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Phase Analysis and Microstructural Investigations of Ce2Zr2O7 for High-Temperature Coatings on Ni-Base Superalloy Substrates

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High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 38 Issue 2019

Abstract

Crystalline cerium-zirconate (CZ) powders were synthesized via solution-assisted combustion synthesis route and calcined at 850°C for 8 h to obtain coarse crystalline powders. SEM (scanning electron microscopy) characterization studies were done to evaluate the morphology of the powders. XRD analysis of the resulting powder confirmed the presence of crystalline α-Ce2Zr2O7 along with a Ce2Zr2O8 phase having a disordered fluorite cubic lattice. Phase composition, lattice parameters, and the atomic positions were also investigated. Refinement of XRD data was done to quantify the amount of α-Ce2Zr2O7 and Ce2Zr2O8 phases. Ni-base superalloy Inconel 625 was chosen as the coating substrate, and the powders were coated using an air plasma spraying (APS). A thermally grown oxide (TGO)/Al2O3 layer was observed owing to the high temperature of the substrate as well as the diffusion of bond coat material into the substrate. Coated samples were characterized by SEM to study the surface morphology, coating thickness, and interface microstructures. The thickness of the coated sample was found to be 400 μm. Thermal cycling test of the coated sample was carried out at 750°C for 50 h to evaluate the thermal shock resistance of the coating as well as the spalling behavior of the coating. Preliminary oxidation tests were carried out for 50 h at 750°C to evaluate the oxide growth by measuring weight gain of the oxide layers formed. Oxide growth signifies the gradual increment of layers over a period with a parabolic rate constant of about Kp= 1.18 × 10–3 mg2 cm–4 h–1.

Keywords: thermal barrier coatings; combustion synthesis; cerium zirconate; Air Plasma Spraying (APS); NiCrAlY; TGO and oxidation resistance

Introduction

Coatings on superalloy substrates are well known for various intrinsic and extrinsic applications that were governed by the influence of temperatures. An extremely oxidative environment requires protective coatings that do not spall easily. Ceramic coatings having high hardness and wear resistance exposed to thermal and corrosive conditions coupled with relatively low densities offer several advantages over metallic materials. A ceramic top coat has significantly lower thermal conductivity than the metallic substrate, and by applying an internal coating of the components, it is possible to establish a significant temperature drop (several 100 K) across the ceramic layer by suitably selecting materials for Thermal Barrier Coatings (TBCs). During past decades, Yttria Stabilized Zirconia (YSZ) was identified as one of the essential ceramic topcoat material developed in the last 30 years [1]. Role of the ceramic top coat is to reduce the effect of temperature by insulating, while the metallic bond coat decreases coefficient of thermal expansion (CTE) mismatch between the top coat and the substrate, thus enhancing the efficiency and service life of gas turbines. Among the potential ceramic candidates for TBCs Fluorites, Perovskites, YSZ, Mullites, Lanthanide orthophosphates as well as pyrochlore structures which shows, promising thermophysical properties [1, 2, 3]. The linear Thermal Expansion Coefficient of Lanthanum Cerium Zirconate (LCZ) is higher than that of 8 mol% YSZ when the temperature is above 400°C, but the thermal conductivity of La2Zr2O7 was much lower than that of YSZ. With an increase in temperature, the Thermal Expansion Coefficient of these ceramics increases, while the thermal conductivity decreases [4, 5, 6]. The endurance of the coatings against thermal cycle/shock and its degradation depends on adherence of coating layers as well oxide layer growth on coating surface during service [7, 8]. Though LaAlO3 (LA) is being claimed as a potential oxide metal which can replace YSZ, Not much literatures has been on LaAlO3 coatings. LA has been synthesized and characterized, for their flow-related characteristics, and the capability to deliver stoichiometric perovskite structures [8]. Microstructural studies of layered TBCs showed three coating layers such as an Interfacial layer, bond, and top coats, respectively and the mechanical properties were compared with the common TBCs with a single layer of each coat. The porosities in the top coats of the single structure (TBC-1 and TBC-2) were 19.6% and 10.2%, respectively, and those of the layered structure (TBC-3 and TBC-4) changed from 8.2% to 18.9% [9]. Longer dwell times and higher particle temperatures increase the thickness of the oxide layer and a high concentration of oxide stringers within the bond coat [10]. Growth of the TGO layer is more related to the bond coat properties and chemistry since ZrO2 is stable at high temperature [11]. Thermal Spalling tests were performed for two TBCs samples based on zirconia with different thicknesses in the top and bond coats [12]. Atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) were commonly used techniques for bond coated oxides that are seen as dark, elongated phases that appear in the microstructure, parallel to the interface. Interface roughness of the bond coat was found as one of the likely factors that affect the lifetime of TBC systems [12, 13, 14]. Two types of the bond coat were prepared by different methods namely, APS and HVOF [14]. Hardness and fracture toughness values of TBCs increased due to densification of the top coat during cyclic thermal exposure, and the bond coat prepared by the HVOF process showed higher values than that by APS process. At high temperatures, tensile stresses occur as a result of differences in thermal expansion coefficient and those Stresses driven surface diffusion was proposed as a plausible mechanism of the bond coat rumpling observed in TBCs upon thermal cycling [15, 16]. Some important characteristics of the top coat are high melting temperature, low thermal conductivity, the thermal expansion coefficient by underlying superalloy, resistance to oxidation and corrosion, strain tolerance [16]. At high temperatures, tensile stresses result from differences in thermal expansion coefficient and temperature gradients during rapid thermal cycling are stabilized between the substrate and ceramic layer [16]. The fracture resistance and adhesion behavior of the interfacial Al2O3 scale may also be important issues although these topics have received relatively little attention about plasmasprayed TBCs [17].

With an increase in temperature, the thermal expansion coefficient of La2Zr2O7 ceramics was enhanced. The corresponding reduction in thermal conductivity of La2Zr2O7 can be attributed to the significantly higher concentration of oxygen vacancies and the larger atomic weight of the solute cations in this material [6]. The misfits between the bond coat and substrate are more subtle such that they occur not only from thermal expansion but also from phase transformations and void swelling. Understanding these misfits, ascertaining their importance to system durability, and finding means to control them, has been an important area of research focus. Actual spall formation is preceded by smaller cracks that extend and coalesce along delamination planes, located either within the oxide layer or at the interface between the TGO and the bond coat [18]. Composite powders of Al2O3and Ce2Zr2O7 prepared as the top coat material shows the highest values of KIC (6.5 MPa m−1) and (620 MPa) were achieved in 10 vol% Ce2Zr2O7 composites, sintered more than theoretical density [19].

The phase diagram of CeO2-ZrO2 from Figure 1 shows that cubic solid solution forms CeO2 at ZrO2 (< 10 mol%) below 900°C [20]. High-temperature coating using Ce2Zr2O7 (CZ) has been investigated for oxidation resistance and spalling behavior of the thermally sprayed coatings. Microstructural analysis of coatings shows the formations of the dense compound with a low porosity level of the coatings. This primary investigation generally talks about the improvement of oxidation resistance and how the oxide layer affects the compound stability. The first attempt in developing cerium zirconate (CZ) as a candidate material for the top coat and structural correlations of the phases obtained from the solid solution of CeO2-ZrO2 were made.

Figure 1 Phase diagram of CeO2-ZrO2 reproduced from Saha and D.C Agarwal [21].
Figure 1

Phase diagram of CeO2-ZrO2 reproduced from Saha and D.C Agarwal [21].

Experimental work

Experimentation part consists of the preparation of CZ with a pyrochlore phase and thermal spraying of the powders onto an Inconel 625 substrate followed by the characterization of the coated samples for microstructure, thermal cycling, and oxidation behavior.

Materials and preparation

High purity compounds Cerium nitrate, 98% pure (Ce (NO3)2), Zirconyl Nitrate powder, 99% pure (ZrO(NO3)2), Glycine, 99% pure (CH2NH2COOH), Nitric acid, 10N (HNO3) of analytical grade were used as a precursor for Ce2Zr2O7 powders. The synthesis technique used here is solution assisted combustion technique with precursors of Cerium Nitrate Hexahydrate (Ce(NO3)2) and Zirconyl Nitrate (ZrO(NO3)2) along with Glycine (C2H5NO2) as fuel. The stoichiometric property of reactant was prepared based on the reaction.

The stoichiometric reaction is presented below

(1)6Ce(NO3)2+6Zro(NO3)2+10C2H5NO2→3Ce2Zr2O7+20CO2                 +20N2+67H2O

The synthesis was carried out by dissolving each of the reactants in nitric acid, and the complete mixing of the powders into the solution was ensured. Zirconyl nitrate solution was treated with cerium nitrate solution initially. Glycine was dissolved in distilled water and then added in drops to the mixture with the slow stirring rate. The whole mixture was stirred for about 45 min with mild heating until a clear solution was obtained. This solution mixture was transferred to an alumina crucible and was kept in a muffle furnace at 923 K (650°C) for 10 to 15 min per batch to obtain the powders. Finally, the powders were sintered at 1100°C for the formation of a complete Ce2Zr2O7 pyrochlore phase as were seen in the phase diagram of the CeO2-ZrO2 system [15, 16]. The agglomerate was crushed and sieved, which yielded powders of size 25 μm and above.

Substrate preparation

Inconel 625 samples of dimensions 3 cm × 3.8 cm were taken and sandblasted to get a 100 μm surface roughness to improve coating adherence. Samples surface was then degreased and cleaned with acetone to remove any entrapped silica particles and other foreign particles. Optical emission spectroscopy (OES) was carried out before coating to obtain the composition of the substrate (Table 1).

Table 1

Composition of Inconel 625.

ElementCMnSiPSNiCoNb
Percentage (%)0.080.350.350.0150.01553.501.004.5
ElementCrFeAlMoTiBCu
Percentage (%)19.515.60.83.001.10.0060.15

Thermal spray coating of Inconel sample

A most conventional form of thermal spraying is air plasma spraying (APS) where argon and hydrogen gasses are used as primary and secondary gasses, respectively. Thermal plasma spray (TPS) is a molten droplet deposition technology in which micrometer-sized particles of metals and ceramic powders are introduced into an arc plasma jet, entrained therein and propelled onto a polished substrate. The particles acquire thermal energy and momentum from the thermal plasma; undergo melting, followed by impact on the substrate surface and rapid solidification. Typically, for oxides and even most metallic alloys, plasma spraying is conducted under ambient conditions and hence the term APS (spraying of oxidation-sensitive metals in a low-pressure environment). The resultant deposited materials comprise of an assemblage of “splats” of rapidly solidified materials assembled to form a brick wall structure. Typical powder particle sizes range from 10 to 100 μm with resultant splats of the order of a few microns in thickness and 100–150 μm in diameter. Parameters used for APS coated top coat and bond coat are shown in Table 2.

Table 2

Coating parameters used in preparation of APS bond and top COATS.

ParametersBond CoatTop Coat
(NiCrAlY)(Ce2Zr2O7)
Feed rate (mg/mm)90100
Powder Carrier Gas (l/min)33
Gun to work distance (mm)180150
Current/Voltage (A/V)450/90550/100
Gun speed (mm/s)1010
Primary and secondary gas30/2045/5
(Ar/He)
Step distance (mm)85

Characterization of powders and coated samples

XRD analysis is a rapid analytical technique used for phase identification of a crystalline material and can provide useful information such as crystal structure, unit cell dimensions, and crystallite size. Identification and characterization of compounds can be carried out from the diffraction pattern. In the present work, X’pert High Score plus software, an indigenously developed software with ICDD database, which was used to analyze the crystallographic information on phase formations and their lattice parameters. Also, Structure Prediction Diagnostic Software (SPuDS Version is 2.12.12.20. The software was developed by Michael Lufaso from university of north Florida and Pat Woodward from Ohio state university, United States of America.) was used for analyzing the atomic lattice positions and the bond distance between various atoms. The microstructural study was carried out using a JEOL 600 make Scanning Electron Microscopy. Secondary electron (SE) imaging mode was used to analyze the morphology and size of the powder particles. The coated layers, thickness, and morphology of coating were also analyzed using SEM. Thermal cycling tests were performed using a muffle furnace to check the stability of the coatings, involving repeated heating and cooling cycles for about 10 min duration. Thermal cycling was carried out for 50 cycles, and the microstructural results were analyzed. High-temperature isothermal oxidation studies were conducted to evaluate the coating performance at high temperature and stability. Isothermal oxidations were carried out at 750°C for 50 h to determine the onset of oxide growth relate the ease with which a material develops an oxide layer as well as the stability of the oxides grown. Evaluation of oxide growth was done by taking the rate constant of the oxide layers. By measuring the weight gain of the oxide layer with increasing oxidation times and plotting the weight gain against the oxidation time, the rate constant for the oxidation process was obtained.

Results and discussion

Results of characterization of the CZ powders initially and as well as microstructural analysis and thermal behavior of coated samples are discussed in detail in the following section.

XRD analysis

XRD pattern confirmed the presence of α-Ce2Zr2O7 phase and due to the oxidation of Ce3+ to Ce4+ in the Ce2Zr2O7 phase converts the resultant phase as β-Ce2Zr2O8 as very well agreed with the previous literature results [22]. A sharp color change during the calcination process exhibits a distinct light yellowish color after the final transformation. It has a stable structure up to 1600°C similar to Ce2Zr2O7 as well agreed with a phase diagram. Identification of the Ce2Zr2O7 and Ce2Zr2O8 phases are primarily understood concerning the change in lattice parameters. From the XRD pattern shown in Figure 2, the CZ has formed with a different phase composition β-Ce2Zr2O8 along with traces of Ce2Zr2O7, indicating the incomplete transformations of the powders during calcinations. Structure of β-Ce2Zr2O8 reveals the presence of disordered cubic fluorite structure with a pyrochlore form. Pyrochlore generally possesses a structure of cations occupying seven-eighths of the tetrahedral sites with Wycoff positions (special atomic sites) 48f and 8a sites between the cations. Peaks corresponding to 29.18°, 33.82°, 48.59° and 57.67° shows the existence of α-Ce2Zr2O8 peaks matching with the intensities of the cubic phase of (222), (400), (440), (622) and (444) planes, while the peak at 70.7° showed the presence of Ce2Zr2O7 and the reference pattern correctly matched with JCPDF no 052–1104.

Figure 2 XRD analysis of synthesized Ce2Zr2O8 powders.
Figure 2

XRD analysis of synthesized Ce2Zr2O8 powders.

The lattice parameter calculated using above crystallographic data was found to be 10.589 A°, and interfacial angles were 90° each, the volume of the unit cell was found to be 1187.31 A°3. (Table 3)

Table 3

Parameters of Ce2Zr2O8 powders calculated from XRD pattern.

S.no2Theta[°](hkl) Valuesd-spacing[A°]
129.180(222)3.058
233.824(400)2.640
348.596(440)1.872
457.677(622)1.597
570.702(444)1.526

The fractional amount of Ce2Zr2O8 (CZ) formed was estimated from the relative intensities ratio of the primary phase with the secondary phase compounds using the equation given below [20],

(2)%Xcz=I(222)I(222)+I(444)

The above equation can be modified depending on the Miller indices of the specific phases present. The presence of Ce2Zr2O8 phase was estimated using eq. (2). Increasing the sintering temperature to 1200°C improved the phase purity of the compound to 100% with an accompanying increase in grain size of the calcined powders. Lattice parameters and interplanar spacings are calculated as per the standard procedures used in X’Pert High Score plus software.

From the precursors, of ZrO2-CeO2 few other phases were observed along with primary CZ phase. Ceria (CeO2) substitution into the ZrO2 solid solution affects the untransformed Ce2Zr2O7 associated with some lattice strain and has good agreement with the previous literature [22]. Hence the Ce2Zr2O7 phase was analyzed at the peak positions 58.02, 71.01 and 43.62 respectively and found to exactly match the tetragonal structure of CZ as strongly agreed with previous findings [20, 22]. These untransformed tetragonal crystals give rise to the small amount of peak shift as well as peak broadening in the XRD pattern of the CZ powders. Peak broadening associated with the FWHM is a significant factor, and it is found to vary for each peak position. Hence the values of each FWHM determined by using the high score plus software are shown in Table 5. Debye-Scherer formulae (eq. 5) use the FWHM values obtained from the broadening effect of each peak in order to calculate the average crystallite size [19].

Table 5

FWHM values corresponding to the peak positions.

S.no2 theta [o]FWHM[o]
129.1800.207
233.8240.310
348.4960.392
457.6770.400
560.5020.410
(3)D=0.9λ/βcosθ

D – Crystalite size (nm)

λ – Wavelength source

β – FWHM (°)

Crystallite sizes calculated using the above equation (Table 4), shows the presence of fine crystalline CZ phase (Figure 2) with minimum peak broadening,

Table 4

Crystallite size for Ce2Zr2O8 calculated (using Debye-Scherer equation).

S.noPeak Position [o]FWHM [o]Crystallite size (nm)
129.1800.2076.91
233.8240.3104.67
348.4960.3923.87
457.6770.4003.95
560.5020.4103.90

indicating a small amount of lattice strain during phase transformations. Phase quantification shows more broadened peaks that are observed predominantly for Ce2Zr2O8 phases, which indicates a small crystallite size with an average value of 4.66 nm.

The structural refinement of the unit cell data was done using the SPuDS. The primary purpose of using this software is to predict the cell parameters, atomic structural positions along with the bond valence strength calculation of each atom present in the unit cell. Results of SPuDS analysis of pyrochlore structure are presented in Table 6.

Table 6

Summary of results for unit cell refinements [22].

AtomBand valenceOxidation statesOccupancyAtomic sites
Ce2.95931.0016d
Zr3.99841.0016c
O11.89321.0048f
O22.55520.088b
O32.35420.928a

Space group analysis of the phases formed was carried out and found to be the Fd-3 m group for Ce2Zr2O7 and P213 group for Ce2Zr2O8 corresponding to the space group number 227, which confirms the ideal pyrochlore structure. Unit cell parameters obtained from structural analysis were found to be 10.707 Å, and the volume of unit cell was 1225.387 Å3, respectively. The secondary phase observed in the XRD analysis has a space group of P42/nmc with the space group number 137 thereby confirming the presence of primitive tetragonal lattices. The oxygen vacancies occupy 1/8th of the tetrahedral sites (8b) sites and found to have an ordered Ce2Zr2O7 structure. Before oxidation, the oxygen ions initially occupied 8b sites while Ce and Zr ions occupied 16c and 16d sites, respectively. Oxygen atoms remain the same positions before and after oxidation. The site 8a coordinates with four Ce ions and the 8b sites coordinated with 4Ce ions, the 8b sites with 4 Zr ions and the 48f sites coordinated with 2 Ce and 2 Zr ions. Earlier refinement results show that the 48f and oxygen sites have full occupancies, and also the 48f site always occupies as 1 [22].

Details of the occupancy state of various atoms with the atomic coordinates (Table 7) along with the calculated bond distance and valence states are tabulated Table 8.

Table 7

Occupancy state with the atomic coordinates for various atoms.

AtomsSitesXYZOccupancy
Ce16d0.50000.50000.50001.00
Zr16c0.0000.00000.00001.00
O148f0.33040.12500.12501.00
O28b0.12500.12500.12500.08
O38a0000.92
Table 8

Bond distance and valencies data.

A sitesX sitesMultiplication factorDistanceValencyOccupancy
Ce(16d)O(48f)x62.6210.29361.000
Ce(16d)O(8b)x22.3160.24341.000
B SitesX sitesMultiplication factorDistanceValencyOccupancy
Zr(16c)O(48f)x62.0780.10931.000

Tables 7 and 8 relate the atomic positions by the distance between the cations to anions (both A & B sites) together with their occupancies shall be used for the further refinements using the Rietveld method.

Microstructural analysis of coated specimens

Observations of thermally grown oxide (TGO)

SEM investigations provided useful information on microstructural features such as phases present, pores, microcrack formations as well as the formation of TGO. SEM characterization of TBC of as-coated specimens was used to analyze the total coating thickness consisting of both topcoat and bond coat. SEM images of the cross-section in the vicinity of the Ce2Zr2O8/NiCrAlY interface are shown in Figure 3(a) and (b).

Figure 3 (a) Cross section of Ce2Zr2O8, (b) NiCrAlY interface.
Figure 3

(a) Cross section of Ce2Zr2O8, (b) NiCrAlY interface.

SEM micrograph (Figure 3(a) and (b)) confirms the presence of a thin TGO layer at the Ce2Zr2O8/NiCrAlY interface with an increased thickness of about 16 μm due to inward diffusion phenomenon of oxygen. Micrograph of the TGO layer also reveals that nonuniform variations in thickness at the Ce2Zr2O8/NiCrAlY interface. This TGO layer is primarily a composite consisting of two layers observed with the contrasting colors one with black layer closer to the bond coat layer, and the gray layer near the CZ phase.

SEM micrograph (Figure 4) of the TGO layer at higher magnification shows the presence of pores and nonuniformly sized particles, especially in the gray layer. Consequently, the TGO layer was identified as Al2O3 (alumina) that usually appears gray (Figure 3) which is in agreement with the previous literature [16, 17].

In air plasma sprayed (APS) samples, inter-splat pores result from the impingement of molten droplets onto micro-cracks and fine grain boundaries. These pores provide a high impedance to heat flow along the thickness of the coating resulting in a TBC with low thermal conductivity. It was observed that the ideal α-Al2O3 (TGO) layer grow on the bond coat both during top coat depositions as well as during component service. Interconnected porosity exists in the coating allows easy diffusion of oxygen from the service environment to the bond coats as illustrated by J.A Haynes et al., during the investigations of the various MCrAlX bond, coats have reported similar observations [17]. The growth rate of the TGO usually follows parabolic growth law given by eq. (4) [7],

Figure 4 SEM micrograph of TGO at higher magnification.
Figure 4

SEM micrograph of TGO at higher magnification.

(4)h2=2 Kp.t

where,

h is the thickness,(μm)

t is the time (sec) and

Kp is the parabolic rate constant (mg2cm−4hour−1)

Thermal cycling studies on coated samples

Thermal stability of the coating was carried out by thermal cycling to check the coating adherence along with the coating shock resistance behavior during the operating temperatures. During the operation of aero gas turbine engines, the coating system is subjected to thermal cycles that increase the bond coat surface temperature close to 1000°C [17, 23]. Under this condition, the temperature difference between the top coat and bond coat may exceed 100°C or more. In the present research, coated samples were subjected to thermal cycling at 850°C with each cycle involving 10 min of alternate heating and cooling.

SEM micrograph (Figure 5) of thermal cycled samples showed that the coating exhibits a strong adherence to the substrate up to 50 cycles with the very minimal amount of distortion. Thermal spalling was not observed until the 20thcycles, and from the micrograph, coating is found to be strongly adherent thereby lowering the coating distortion rate. At this temperature, significant densification of the CZO (sintering) as well as creep of the bond coat occurs and is found to be accompanied by temperature dependent TGO layer growth. However, as the number of thermal cycles increased, the thermal stresses developed by these processes eventually cause spallation of the TBCs, which usually occurs at the Ce2Zr2O8/NiCrAlY interface due to the thermal stress developed. The spallation results from the linkage of the cracks formed in the TBC layer above the TGO.

Figure 5 Thermal cycled at 50th cycle.
Figure 5

Thermal cycled at 50th cycle.

From Figure 5, the failure observed during the thermal cycling might have occurred due to the following reasons and is consistent with the previous literature findings. Abdullah Cahit et al. have reported similar results. [7],

a) Large in-plane compressive stresses in TGO, especially during cooling, leading to rumpling of the coating.

b) During the TGO growth, imperfections exist (or developed) around the TGO. Tensile stresses are induced normal to the TGO/Bond Coat interface, which facilitates crack initiation during early stages at the interface.

Investigation of high-temperature oxidation behavior of coated samples

Isothermal oxidation behavior varies non linearly with the weight gain of the oxide with respect to time in hours. This formed oxide layer was observed to have a mixed type of oxide layer growth, which is again a predominant factor in predicting the lifetime of CZ coatings. Variation in thickness of alumina and mixed oxide layer increases as a function of aging time and the relationship between the average thickness of each layer and aging time was also established to explain the oxidation kinetics of the material.

A plot of weight gain of the oxide layers concerning time (Figure 6) and the slope value gives the rate constant Kp as 1.18 × 10–3 mg2cm−4hour−1, indicating a parabolic growth rate of oxide layers with respect to time. Mohamed Morsi et al. [16] have reported a similar parabolic growth rate in the case of TBCs.

Figure 6 Plot of weight gain as a function of time during oxidation of coated samples.
Figure 6

Plot of weight gain as a function of time during oxidation of coated samples.

Towards observing CZO layer as the top coat that has a little thickness variation despite an increase in aging time. Further, the thickness of the TGO layer gradually increases with aging time. The relationship between TGO thickness and the square root of time shows that the growth of mixed oxide obeys the parabolic law. Hence, the mixed oxide is protective despite the presence of porosity in the coating.

Influence of defects on the coating

SEM micrograph of the oxidized sample shows (Figure 7), the presence of microcracks and porosity in the coating both in CZ and TGO layers of aged specimens. The amount of porosity, as well as the micro cracks in each layer, increased with aging time. In particular, the micro cracks in the CZ top layer increased notably, while the porosities present in the mixed oxide also showed an

Figure 7 SEM micrograph showing the formation of cracks in the mixed oxide layers.
Figure 7

SEM micrograph showing the formation of cracks in the mixed oxide layers.

increase in micro-cracks formations in the alumina layer (TGO). The reason because the porosity and microcrack in the CZO layer are formed due to thermal expansion mismatch accompanying the formation and growth of TGO which is in agreement with the result of a previous study [7]. Further, the formation of various porosities in the mixed oxide is caused by Kirkendall porosity caused by the difference in diffusion rate between the top coat and TGO layer [11].

Formation of defects such as micro crack or porosity in the coated specimens increases the stress in the vicinity of the crack tip. Accordingly, a macro-crack or delamination could initiate from the tip of the defects. Hence, the presence of porosities both at the top coat and at the interface zone improves the conductivity by facilitating the inward diffusion of oxygen. Thus it is evident that the thermal conductivity of the top coat gets reduced Sang-Won Myoung et al. [9] have reported a similar result during an investigation on YSZ coatings over a nickel base superalloy substrate.

Conclusions

Major conclusions from the present work are:

  1. Synthesis of CZ by solution assisted combustion synthesis was carried out.

  2. XRD analysis confirmed the presence of nearly pure Cerium zirconate (Ce2Zr2O7) compound along with a minimal amount of secondary phase constituents.

  3. SEM micrograph and the crystallite size obtained from XRD confirmed the nanocrystalline nature of CZ.

  4. SEM micrographs before and after coating show the presence of various layers (Topcoat, Bond coat with CZO/NiCrYAl interface zone).

  5. SEM investigations on thermal cycled confirmed that the coating exhibits excellent adherence to the substrate.

  6. Limited porosity and microcracks were observed after the thermal cycling of specimens, which indicated that the coating has better compatibility along with lower thermal conductivity.

  7. Results of studies on weight gain as a function of time during oxidation studies indicated a parabolic growth with a constant of Kp= 1.18×10−3mg2cm−4hour−1, indicating the protective nature of coatings.

https://orcid.org/0000-0001-5216-7273

Acknowledgements

The authors are grateful to the Management and Department of Metallurgical Engineering, PSG College of Technology, Coimbatore. Also, it gives us a great privilege to acknowledge Dr L. John Berchmans, Principal scientist and head, Pyrometallurgy division, Central electrochemical research institute –CSIR, Karaikudi, India for extending the facilities to carry out this investigation.

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Received: 2018-04-07
Accepted: 2018-12-03
Published Online: 2019-10-01
Published in Print: 2019-02-25

© 2019 Venkatesh et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 Public License.

Articles in the same Issue

  1. Frontmatter
  2. Review Article
  3. Research on the Influence of Furnace Structure on Copper Cooling Stave Life
  4. Influence of High Temperature Oxidation on Hydrogen Absorption and Degradation of Zircaloy-2 and Zr 700 Alloys
  5. Correlation between Travel Speed, Microstructure, Mechanical Properties and Wear Characteristics of Ni-Based Hardfaced Deposits over 316LN Austenitic Stainless Steel
  6. Factors Influencing Gas Generation Behaviours of Lump Coal Used in COREX Gasifier
  7. Experiment Research on Pulverized Coal Combustion in the Tuyere of Oxygen Blast Furnace
  8. Phosphate Capacities of CaO–FeO–SiO2–Al2O3/Na2O/TiO2 Slags
  9. Microstructure and Interface Bonding Strength of WC-10Ni/NiCrBSi Composite Coating by Vacuum Brazing
  10. Refill Friction Stir Spot Welding of Dissimilar 6061/7075 Aluminum Alloy
  11. Solvothermal Synthesis and Magnetic Properties of Monodisperse Ni0.5Zn0.5Fe2O4 Hollow Nanospheres
  12. On the Capability of Logarithmic-Power Model for Prediction of Hot Deformation Behavior of Alloy 800H at High Strain Rates
  13. 3D Heat Conductivity Model of Mold Based on Node Temperature Inheritance
  14. 3D Microstructure and Micromechanical Properties of Minerals in Vanadium-Titanium Sinter
  15. Effect of Martensite Structure and Carbide Precipitates on Mechanical Properties of Cr-Mo Alloy Steel with Different Cooling Rate
  16. The Interaction between Erosion Particle and Gas Stream in High Temperature Gas Burner Rig for Thermal Barrier Coatings
  17. Permittivity Study of a CuCl Residue at 13–450 °C and Elucidation of the Microwave Intensification Mechanism for Its Dechlorination
  18. Study on Carbothermal Reduction of Titania in Molten Iron
  19. The Sequence of the Phase Growth during Diffusion in Ti-Based Systems
  20. Growth Kinetics of CoB–Co2B Layers Using the Powder-Pack Boriding Process Assisted by a Direct Current Field
  21. High-Temperature Flow Behaviour and Constitutive Equations for a TC17 Titanium Alloy
  22. Research on Three-Roll Screw Rolling Process for Ti6Al4V Titanium Alloy Bar
  23. Continuous Cooling Transformation of Undeformed and Deformed High Strength Crack-Arrest Steel Plates for Large Container Ships
  24. Formation Mechanism and Influence Factors of the Sticker between Solidified Shell and Mold in Continuous Casting of Steel
  25. Casting Defects in Transition Layer of Cu/Al Composite Castings Prepared Using Pouring Aluminum Method and Their Formation Mechanism
  26. Effect of Current on Segregation and Inclusions Characteristics of Dual Alloy Ingot Processed by Electroslag Remelting
  27. Investigation of Growth Kinetics of Fe2B Layers on AISI 1518 Steel by the Integral Method
  28. Microstructural Evolution and Phase Transformation on the X-Y Surface of Inconel 718 Ni-Based Alloys Fabricated by Selective Laser Melting under Different Heat Treatment
  29. Characterization of Mn-Doped Co3O4 Thin Films Prepared by Sol Gel-Based Dip-Coating Process
  30. Deposition Characteristics of Multitrack Overlayby Plasma Transferred Arc Welding on SS316Lwith Co-Cr Based Alloy – Influence ofProcess Parameters
  31. Elastic Moduli and Elastic Constants of Alloy AuCuSi With FCC Structure Under Pressure
  32. Effect of Cl on Softening and Melting Behaviors of BF Burden
  33. Effect of MgO Injection on Smelting in a Blast Furnace
  34. Structural Characteristics and Hydration Kinetics of Oxidized Steel Slag in a CaO-FeO-SiO2-MgO System
  35. Optimization of Microwave-Assisted Oxidation Roasting of Oxide–Sulphide Zinc Ore with Addition of Manganese Dioxide Using Response Surface Methodology
  36. Hydraulic Study of Bubble Migration in Liquid Titanium Alloy Melt during Vertical Centrifugal Casting Process
  37. Investigation on Double Wire Metal Inert Gas Welding of A7N01-T4 Aluminum Alloy in High-Speed Welding
  38. Oxidation Behaviour of Welded ASTM-SA210 GrA1 Boiler Tube Steels under Cyclic Conditions at 900°C in Air
  39. Study on the Evolution of Damage Degradation at Different Temperatures and Strain Rates for Ti-6Al-4V Alloy
  40. Pack-Boriding of Pure Iron with Powder Mixtures Containing ZrB2
  41. Evolution of Interfacial Features of MnO-SiO2 Type Inclusions/Steel Matrix during Isothermal Heating at Low Temperatures
  42. Effect of MgO/Al2O3 Ratio on Viscosity of Blast Furnace Primary Slag
  43. The Microstructure and Property of the Heat Affected zone in C-Mn Steel Treated by Rare Earth
  44. Microwave-Assisted Molten-Salt Facile Synthesis of Chromium Carbide (Cr3C2) Coatings on the Diamond Particles
  45. Effects of B on the Hot Ductility of Fe-36Ni Invar Alloy
  46. Impurity Distribution after Solidification of Hypereutectic Al-Si Melts and Eutectic Al-Si Melt
  47. Induced Electro-Deposition of High Melting-Point Phases on MgO–C Refractory in CaO–Al2O3–SiO2 – (MgO) Slag at 1773 K
  48. Microstructure and Mechanical Properties of 14Cr-ODS Steels with Zr Addition
  49. A Review of Boron-Rich Silicon Borides Basedon Thermodynamic Stability and Transport Properties of High-Temperature Thermoelectric Materials
  50. Siliceous Manganese Ore from Eastern India:A Potential Resource for Ferrosilicon-Manganese Production
  51. A Strain-Compensated Constitutive Model for Describing the Hot Compressive Deformation Behaviors of an Aged Inconel 718 Superalloy
  52. Surface Alloys of 0.45 C Carbon Steel Produced by High Current Pulsed Electron Beam
  53. Deformation Behavior and Processing Map during Isothermal Hot Compression of 49MnVS3 Non-Quenched and Tempered Steel
  54. A Constitutive Equation for Predicting Elevated Temperature Flow Behavior of BFe10-1-2 Cupronickel Alloy through Double Multiple Nonlinear Regression
  55. Oxidation Behavior of Ferritic Steel T22 Exposed to Supercritical Water
  56. A Multi Scale Strategy for Simulation of Microstructural Evolutions in Friction Stir Welding of Duplex Titanium Alloy
  57. Partition Behavior of Alloying Elements in Nickel-Based Alloys and Their Activity Interaction Parameters and Infinite Dilution Activity Coefficients
  58. Influence of Heating on Tensile Physical-Mechanical Properties of Granite
  59. Comparison of Al-Zn-Mg Alloy P-MIG Welded Joints Filled with Different Wires
  60. Microstructure and Mechanical Properties of Thick Plate Friction Stir Welds for 6082-T6 Aluminum Alloy
  61. Research Article
  62. Kinetics of oxide scale growth on a (Ti, Mo)5Si3 based oxidation resistant Mo-Ti-Si alloy at 900-1300∘C
  63. Calorimetric study on Bi-Cu-Sn alloys
  64. Mineralogical Phase of Slag and Its Effect on Dephosphorization during Converter Steelmaking Using Slag-Remaining Technology
  65. Controllability of joint integrity and mechanical properties of friction stir welded 6061-T6 aluminum and AZ31B magnesium alloys based on stationary shoulder
  66. Cellular Automaton Modeling of Phase Transformation of U-Nb Alloys during Solidification and Consequent Cooling Process
  67. The effect of MgTiO3Adding on Inclusion Characteristics
  68. Cutting performance of a functionally graded cemented carbide tool prepared by microwave heating and nitriding sintering
  69. Creep behaviour and life assessment of a cast nickel – base superalloy MAR – M247
  70. Failure mechanism and acoustic emission signal characteristics of coatings under the condition of impact indentation
  71. Reducing Surface Cracks and Improving Cleanliness of H-Beam Blanks in Continuous Casting — Improving continuous casting of H-beam blanks
  72. Rhodium influence on the microstructure and oxidation behaviour of aluminide coatings deposited on pure nickel and nickel based superalloy
  73. The effect of Nb content on precipitates, microstructure and texture of grain oriented silicon steel
  74. Effect of Arc Power on the Wear and High-temperature Oxidation Resistances of Plasma-Sprayed Fe-based Amorphous Coatings
  75. Short Communication
  76. Novel Combined Feeding Approach to Produce Quality Al6061 Composites for Heat Sinks
  77. Research Article
  78. Micromorphology change and microstructure of Cu-P based amorphous filler during heating process
  79. Controlling residual stress and distortion of friction stir welding joint by external stationary shoulder
  80. Research on the ingot shrinkage in the electroslag remelting withdrawal process for 9Cr3Mo roller
  81. Production of Mo2NiB2 Based Hard Alloys by Self-Propagating High-Temperature Synthesis
  82. The Morphology Analysis of Plasma-Sprayed Cast Iron Splats at Different Substrate Temperatures via Fractal Dimension and Circularity Methods
  83. A Comparative Study on Johnson–Cook, Modified Johnson–Cook, Modified Zerilli–Armstrong and Arrhenius-Type Constitutive Models to Predict Hot Deformation Behavior of TA2
  84. Dynamic absorption efficiency of paracetamol powder in microwave drying
  85. Preparation and Properties of Blast Furnace Slag Glass Ceramics Containing Cr2O3
  86. Influence of unburned pulverized coal on gasification reaction of coke in blast furnace
  87. Effect of PWHT Conditions on Toughness and Creep Rupture Strength in Modified 9Cr-1Mo Steel Welds
  88. Role of B2O3 on structure and shear-thinning property in CaO–SiO2–Na2O-based mold fluxes
  89. Effect of Acid Slag Treatment on the Inclusions in GCr15 Bearing Steel
  90. Recovery of Iron and Zinc from Blast Furnace Dust Using Iron-Bath Reduction
  91. Phase Analysis and Microstructural Investigations of Ce2Zr2O7 for High-Temperature Coatings on Ni-Base Superalloy Substrates
  92. Combustion Characteristics and Kinetics Study of Pulverized Coal and Semi-Coke
  93. Mechanical and Electrochemical Characterization of Supersolidus Sintered Austenitic Stainless Steel (316 L)
  94. Synthesis and characterization of Cu doped chromium oxide (Cr2O3) thin films
  95. Ladle Nozzle Clogging during casting of Silicon-Steel
  96. Thermodynamics and Industrial Trial on Increasing the Carbon Content at the BOF Endpoint to Produce Ultra-Low Carbon IF Steel by BOF-RH-CSP Process
  97. Research Article
  98. Effect of Boundary Conditions on Residual Stresses and Distortion in 316 Stainless Steel Butt Welded Plate
  99. Numerical Analysis on Effect of Additional Gas Injection on Characteristics around Raceway in Melter Gasifier
  100. Variation on thermal damage rate of granite specimen with thermal cycle treatment
  101. Effects of Fluoride and Sulphate Mineralizers on the Properties of Reconstructed Steel Slag
  102. Effect of Basicity on Precipitation of Spinel Crystals in a CaO-SiO2-MgO-Cr2O3-FeO System
  103. Review Article
  104. Exploitation of Mold Flux for the Ti-bearing Welding Wire Steel ER80-G
  105. Research Article
  106. Furnace heat prediction and control model and its application to large blast furnace
  107. Effects of Different Solid Solution Temperatures on Microstructure and Mechanical Properties of the AA7075 Alloy After T6 Heat Treatment
  108. Study of the Viscosity of a La2O3-SiO2-FeO Slag System
  109. Tensile Deformation and Work Hardening Behaviour of AISI 431 Martensitic Stainless Steel at Elevated Temperatures
  110. The Effectiveness of Reinforcement and Processing on Mechanical Properties, Wear Behavior and Damping Response of Aluminum Matrix Composites
https://doi.org/10.1515/htmp-2019-0033
Keywords for this article
thermal barrier coatings; combustion synthesis; cerium zirconate; Air Plasma Spraying (APS); NiCrAlY; TGO and oxidation resistance
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BY 4.0

Articles in the same Issue

  1. Frontmatter
  2. Review Article
  3. Research on the Influence of Furnace Structure on Copper Cooling Stave Life
  4. Influence of High Temperature Oxidation on Hydrogen Absorption and Degradation of Zircaloy-2 and Zr 700 Alloys
  5. Correlation between Travel Speed, Microstructure, Mechanical Properties and Wear Characteristics of Ni-Based Hardfaced Deposits over 316LN Austenitic Stainless Steel
  6. Factors Influencing Gas Generation Behaviours of Lump Coal Used in COREX Gasifier
  7. Experiment Research on Pulverized Coal Combustion in the Tuyere of Oxygen Blast Furnace
  8. Phosphate Capacities of CaO–FeO–SiO2–Al2O3/Na2O/TiO2 Slags
  9. Microstructure and Interface Bonding Strength of WC-10Ni/NiCrBSi Composite Coating by Vacuum Brazing
  10. Refill Friction Stir Spot Welding of Dissimilar 6061/7075 Aluminum Alloy
  11. Solvothermal Synthesis and Magnetic Properties of Monodisperse Ni0.5Zn0.5Fe2O4 Hollow Nanospheres
  12. On the Capability of Logarithmic-Power Model for Prediction of Hot Deformation Behavior of Alloy 800H at High Strain Rates
  13. 3D Heat Conductivity Model of Mold Based on Node Temperature Inheritance
  14. 3D Microstructure and Micromechanical Properties of Minerals in Vanadium-Titanium Sinter
  15. Effect of Martensite Structure and Carbide Precipitates on Mechanical Properties of Cr-Mo Alloy Steel with Different Cooling Rate
  16. The Interaction between Erosion Particle and Gas Stream in High Temperature Gas Burner Rig for Thermal Barrier Coatings
  17. Permittivity Study of a CuCl Residue at 13–450 °C and Elucidation of the Microwave Intensification Mechanism for Its Dechlorination
  18. Study on Carbothermal Reduction of Titania in Molten Iron
  19. The Sequence of the Phase Growth during Diffusion in Ti-Based Systems
  20. Growth Kinetics of CoB–Co2B Layers Using the Powder-Pack Boriding Process Assisted by a Direct Current Field
  21. High-Temperature Flow Behaviour and Constitutive Equations for a TC17 Titanium Alloy
  22. Research on Three-Roll Screw Rolling Process for Ti6Al4V Titanium Alloy Bar
  23. Continuous Cooling Transformation of Undeformed and Deformed High Strength Crack-Arrest Steel Plates for Large Container Ships
  24. Formation Mechanism and Influence Factors of the Sticker between Solidified Shell and Mold in Continuous Casting of Steel
  25. Casting Defects in Transition Layer of Cu/Al Composite Castings Prepared Using Pouring Aluminum Method and Their Formation Mechanism
  26. Effect of Current on Segregation and Inclusions Characteristics of Dual Alloy Ingot Processed by Electroslag Remelting
  27. Investigation of Growth Kinetics of Fe2B Layers on AISI 1518 Steel by the Integral Method
  28. Microstructural Evolution and Phase Transformation on the X-Y Surface of Inconel 718 Ni-Based Alloys Fabricated by Selective Laser Melting under Different Heat Treatment
  29. Characterization of Mn-Doped Co3O4 Thin Films Prepared by Sol Gel-Based Dip-Coating Process
  30. Deposition Characteristics of Multitrack Overlayby Plasma Transferred Arc Welding on SS316Lwith Co-Cr Based Alloy – Influence ofProcess Parameters
  31. Elastic Moduli and Elastic Constants of Alloy AuCuSi With FCC Structure Under Pressure
  32. Effect of Cl on Softening and Melting Behaviors of BF Burden
  33. Effect of MgO Injection on Smelting in a Blast Furnace
  34. Structural Characteristics and Hydration Kinetics of Oxidized Steel Slag in a CaO-FeO-SiO2-MgO System
  35. Optimization of Microwave-Assisted Oxidation Roasting of Oxide–Sulphide Zinc Ore with Addition of Manganese Dioxide Using Response Surface Methodology
  36. Hydraulic Study of Bubble Migration in Liquid Titanium Alloy Melt during Vertical Centrifugal Casting Process
  37. Investigation on Double Wire Metal Inert Gas Welding of A7N01-T4 Aluminum Alloy in High-Speed Welding
  38. Oxidation Behaviour of Welded ASTM-SA210 GrA1 Boiler Tube Steels under Cyclic Conditions at 900°C in Air
  39. Study on the Evolution of Damage Degradation at Different Temperatures and Strain Rates for Ti-6Al-4V Alloy
  40. Pack-Boriding of Pure Iron with Powder Mixtures Containing ZrB2
  41. Evolution of Interfacial Features of MnO-SiO2 Type Inclusions/Steel Matrix during Isothermal Heating at Low Temperatures
  42. Effect of MgO/Al2O3 Ratio on Viscosity of Blast Furnace Primary Slag
  43. The Microstructure and Property of the Heat Affected zone in C-Mn Steel Treated by Rare Earth
  44. Microwave-Assisted Molten-Salt Facile Synthesis of Chromium Carbide (Cr3C2) Coatings on the Diamond Particles
  45. Effects of B on the Hot Ductility of Fe-36Ni Invar Alloy
  46. Impurity Distribution after Solidification of Hypereutectic Al-Si Melts and Eutectic Al-Si Melt
  47. Induced Electro-Deposition of High Melting-Point Phases on MgO–C Refractory in CaO–Al2O3–SiO2 – (MgO) Slag at 1773 K
  48. Microstructure and Mechanical Properties of 14Cr-ODS Steels with Zr Addition
  49. A Review of Boron-Rich Silicon Borides Basedon Thermodynamic Stability and Transport Properties of High-Temperature Thermoelectric Materials
  50. Siliceous Manganese Ore from Eastern India:A Potential Resource for Ferrosilicon-Manganese Production
  51. A Strain-Compensated Constitutive Model for Describing the Hot Compressive Deformation Behaviors of an Aged Inconel 718 Superalloy
  52. Surface Alloys of 0.45 C Carbon Steel Produced by High Current Pulsed Electron Beam
  53. Deformation Behavior and Processing Map during Isothermal Hot Compression of 49MnVS3 Non-Quenched and Tempered Steel
  54. A Constitutive Equation for Predicting Elevated Temperature Flow Behavior of BFe10-1-2 Cupronickel Alloy through Double Multiple Nonlinear Regression
  55. Oxidation Behavior of Ferritic Steel T22 Exposed to Supercritical Water
  56. A Multi Scale Strategy for Simulation of Microstructural Evolutions in Friction Stir Welding of Duplex Titanium Alloy
  57. Partition Behavior of Alloying Elements in Nickel-Based Alloys and Their Activity Interaction Parameters and Infinite Dilution Activity Coefficients
  58. Influence of Heating on Tensile Physical-Mechanical Properties of Granite
  59. Comparison of Al-Zn-Mg Alloy P-MIG Welded Joints Filled with Different Wires
  60. Microstructure and Mechanical Properties of Thick Plate Friction Stir Welds for 6082-T6 Aluminum Alloy
  61. Research Article
  62. Kinetics of oxide scale growth on a (Ti, Mo)5Si3 based oxidation resistant Mo-Ti-Si alloy at 900-1300∘C
  63. Calorimetric study on Bi-Cu-Sn alloys
  64. Mineralogical Phase of Slag and Its Effect on Dephosphorization during Converter Steelmaking Using Slag-Remaining Technology
  65. Controllability of joint integrity and mechanical properties of friction stir welded 6061-T6 aluminum and AZ31B magnesium alloys based on stationary shoulder
  66. Cellular Automaton Modeling of Phase Transformation of U-Nb Alloys during Solidification and Consequent Cooling Process
  67. The effect of MgTiO3Adding on Inclusion Characteristics
  68. Cutting performance of a functionally graded cemented carbide tool prepared by microwave heating and nitriding sintering
  69. Creep behaviour and life assessment of a cast nickel – base superalloy MAR – M247
  70. Failure mechanism and acoustic emission signal characteristics of coatings under the condition of impact indentation
  71. Reducing Surface Cracks and Improving Cleanliness of H-Beam Blanks in Continuous Casting — Improving continuous casting of H-beam blanks
  72. Rhodium influence on the microstructure and oxidation behaviour of aluminide coatings deposited on pure nickel and nickel based superalloy
  73. The effect of Nb content on precipitates, microstructure and texture of grain oriented silicon steel
  74. Effect of Arc Power on the Wear and High-temperature Oxidation Resistances of Plasma-Sprayed Fe-based Amorphous Coatings
  75. Short Communication
  76. Novel Combined Feeding Approach to Produce Quality Al6061 Composites for Heat Sinks
  77. Research Article
  78. Micromorphology change and microstructure of Cu-P based amorphous filler during heating process
  79. Controlling residual stress and distortion of friction stir welding joint by external stationary shoulder
  80. Research on the ingot shrinkage in the electroslag remelting withdrawal process for 9Cr3Mo roller
  81. Production of Mo2NiB2 Based Hard Alloys by Self-Propagating High-Temperature Synthesis
  82. The Morphology Analysis of Plasma-Sprayed Cast Iron Splats at Different Substrate Temperatures via Fractal Dimension and Circularity Methods
  83. A Comparative Study on Johnson–Cook, Modified Johnson–Cook, Modified Zerilli–Armstrong and Arrhenius-Type Constitutive Models to Predict Hot Deformation Behavior of TA2
  84. Dynamic absorption efficiency of paracetamol powder in microwave drying
  85. Preparation and Properties of Blast Furnace Slag Glass Ceramics Containing Cr2O3
  86. Influence of unburned pulverized coal on gasification reaction of coke in blast furnace
  87. Effect of PWHT Conditions on Toughness and Creep Rupture Strength in Modified 9Cr-1Mo Steel Welds
  88. Role of B2O3 on structure and shear-thinning property in CaO–SiO2–Na2O-based mold fluxes
  89. Effect of Acid Slag Treatment on the Inclusions in GCr15 Bearing Steel
  90. Recovery of Iron and Zinc from Blast Furnace Dust Using Iron-Bath Reduction
  91. Phase Analysis and Microstructural Investigations of Ce2Zr2O7 for High-Temperature Coatings on Ni-Base Superalloy Substrates
  92. Combustion Characteristics and Kinetics Study of Pulverized Coal and Semi-Coke
  93. Mechanical and Electrochemical Characterization of Supersolidus Sintered Austenitic Stainless Steel (316 L)
  94. Synthesis and characterization of Cu doped chromium oxide (Cr2O3) thin films
  95. Ladle Nozzle Clogging during casting of Silicon-Steel
  96. Thermodynamics and Industrial Trial on Increasing the Carbon Content at the BOF Endpoint to Produce Ultra-Low Carbon IF Steel by BOF-RH-CSP Process
  97. Research Article
  98. Effect of Boundary Conditions on Residual Stresses and Distortion in 316 Stainless Steel Butt Welded Plate
  99. Numerical Analysis on Effect of Additional Gas Injection on Characteristics around Raceway in Melter Gasifier
  100. Variation on thermal damage rate of granite specimen with thermal cycle treatment
  101. Effects of Fluoride and Sulphate Mineralizers on the Properties of Reconstructed Steel Slag
  102. Effect of Basicity on Precipitation of Spinel Crystals in a CaO-SiO2-MgO-Cr2O3-FeO System
  103. Review Article
  104. Exploitation of Mold Flux for the Ti-bearing Welding Wire Steel ER80-G
  105. Research Article
  106. Furnace heat prediction and control model and its application to large blast furnace
  107. Effects of Different Solid Solution Temperatures on Microstructure and Mechanical Properties of the AA7075 Alloy After T6 Heat Treatment
  108. Study of the Viscosity of a La2O3-SiO2-FeO Slag System
  109. Tensile Deformation and Work Hardening Behaviour of AISI 431 Martensitic Stainless Steel at Elevated Temperatures
  110. The Effectiveness of Reinforcement and Processing on Mechanical Properties, Wear Behavior and Damping Response of Aluminum Matrix Composites
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