Band 65, Heft 10

In this paper, the CoFeMoNiAlCr x coatings with different chromium content ( x  = 0, 0.3, 0.6, 0.9 and 1.2) were prepared by argon arc cladding technology on Q235 steel. The microstructure and phases of the coatings were analyzed by OM, SEM, EDS and XRD. The hardness, wear resistance and corrosion resistance of the coatings were tested by microhardness tester, friction and wear tester and electrochemical workstation. The results show that the highest hardness is obtained in the CoFeMoNiAlCr x =0 high entropy alloy coatings, about 500 HV, which is about 3 times than the hardness of Q235 steel (the substrate). With the chromium content of the CoFeMoNiAlCr x coatings increasing, the wear resistance increases first, and then decreases. When the chromium content is 0.9, the wear resistance of the coating is the highest with the wear loss about 2.6 mg and the friction coefficient about 0.52. The corrosion resistance of the coatings decreases with a small amount of chromium addition. When the Cr content in the coating is close to the atomic ratio, the content of the body-centered cubic phase structure increases, and the face-centered cubic phase structure appears in the coating.

In this study, Al 6061 T6 alloy was joined by friction stir welding method with the same parameters using with different profiled pins. As a result of the experiments carried out, the samples were subjected to metallographic examination, hardness measurements, tensile test and bending test. As a result of the examinations carried out, changes in welding performances were determined with the change of pin profiles. As a result of these changes, it was determined that the pin profile suitable for the applied welding parameters was pyramid. It has been concluded that in the use of triangular profile pins, the welding parameters in question should be higher, and the most important reason for this is that the stir zone is larger.

The transient evolution of oxide was studied after directly adding Ti 3 O 5 powder into HRB400 steel. This experiment was carried out in magnesia crucible with vacuum induction furnace and the intermediate samples were taken at 1, 5, 10, and 15 min after Ti 3 O 5 addition. At 20th min, the furnace was powered off to get furnace-cooled cast sample. For intermediate samples, it is found that with increasing treatment time, the titanium content increased though the acid–soluble aluminum content remained stable. Besides, the Ti-bearing oxides were observed by scanning electron microscope (SEM). Moreover, statistical analysis indicated that for Ti-bearing oxide, both number density and titanium content after further normalization increased with increasing processing time. For cast sample, the characteristic of Ti-bearing oxide at different heights are similar. These results confirmed the adding valid of Ti 3 O 5 , which may be due to its decomposition. Finally, after heat treatment, these introduced Ti-bearing oxides can induce the intragranular ferrite nucleation. This indicates the effectiveness of external adding method in oxide metallurgy.

Materials can display multiple mechanical behaviors when they are biaxially stressed. In this research work, films obtained through the blowing process were investigated in order to compare the mechanical properties and behavior of the film under uniaxial and biaxial stress conditions. Bulge test coupled with a continuous full-field strain measurement was undertaken in order to characterize polymeric film in a biaxial stress state. As far as this study is concerned, a laboratory-made pneumatic bulge test machine was used for the determination of the biaxial behavior of a 50 μm thickness PLSF (modified PLA) film. 3D-digital image correlation (3D-DIC) technique was used in order to compute the strain field continuously during the test. Tensile test was equally performed on the film along its machine direction (MD) and transverse direction (TD). Strain field distribution in the film sample was analyzed and compared in both tests. The tensile test results displayed an isotropic behavior of the film in both directions. However, a difference in the strain at break was noticed because of the thickness instability along the TD. The comparison between uniaxial and biaxial properties resulted in almost the same properties with respect to the Young Modulus as well as the tensile strength.

The Cu effect on the microstructure and corrosion resistance of Al–15Mg 2 Si composites was studied. The results showed that Cu addition decreased the average size of primary Mg 2 Si (Mg 2 Si P ) particles, changed the hopper-like Mg 2 Si P particles to polyhedrals, and caused the formation of θ -Al 2 Cu and Q -Al 5 Mg 8 Si 6 Cu 2 compounds in the composite matrix. According to the image analysis results, increasing the Cu content from 0.01 to 5 wt% halved the average size of Mg 2 Si P particles, increased their fraction by about 40 %, and increased the composite porosity content. The electrochemical impedance spectroscopy showed that adding 5 wt% of Cu resulted in an increase of about 3.7 times in the corrosion resistance as compared to Al–15Mg 2 Si composite. The beneficial effects of Cu were also confirmed by the potentiodynamic polarization experiments. Cu addition seems to promote less intense general corrosion than the base alloy’s localized attack.

As an important device to control the drilling direction in the drilling process, centralizer plays an important role in slowing the deviation and improving the casing centering degree. This paper makes a detailed analysis on the fracture failure of centralizer after multiple repair welding. First, the macroscopic appearance of the port is observed by macroscopic inspection. Secondly, the physical and chemical performance analysis shows that all indicators meet the requirements of the indicators. Finally, through the microscopic morphology, energy dispersive spectrometer (EDS) and other means to analyze the port crack source, combined with a variety of tests to find the true cause of fracture failure centralizer. After inspection, it was found that the centralizer was fatigue fracture, and showed multi-source cracking characteristics. Therefore, strict control of centralizer especially after repair welding quality, strengthen the quality inspection of centralizer, to carry out the relevant thermal processing technology research, and further effectively prevent the occurrence of fracture failure.

The main aim of this study is to analyse the influence of tool plunging rate on tool wear and stir zone characteristics of DMR249A high strength low alloy (HSLA) steel joints developed using friction stir welding (FSW). The HSLA steel plates were welded at five levels of tool plunging rates varying from 2.0 mm min −1 to 3.0 mm min −1 . The tool rotational speed of 600 rpm and welding speed of 30 mm min −1 were kept constant during welding. The wear of FSW tool was analysed by microscopic observations of tool condition after welding, stir zone characteristics, weight loss measurement and pin profile analysis. The characterization techniques of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to analyse the microstructural characteristics of stir zone of welded joints. Results disclosed that the severe degradation of FSW tool occurred due to the sudden dynamic impact load on tool pin while plunging and more diffusion of work piece material into the tool pin which leads to insufficient plasticized material flow. The tool plunging rate of 2.5 mm min −1 showed minimum tool wear and produced defect free sound joint.

In this current research paper, the modelling of boron diffusion during the powder-pack boronizing was achieved by utilizing two kinetics approaches: the integral method and average diffusion coefficient (ADC) method. This integral method used a general solution of algebraic differential equations (DAEs) system. The powders mixture composed of: 33.5 wt% B 4 C, 5.4 wt% KBF 4 and 61.1 wt% SiC was employed to generate the Fe 2 B layers on AISI 4147 steel in the interval of 1123–1273 K for 2–8 h. The obtained surface layers have been characterized by Scanning electron microscopy (SEM) to examine the growth front with a typical saw-toothed morphology. The crystalline nature of boride phase has been verified by X-ray diffraction technique (XRD). The calculation results arising from the two models led to the similar boron activation energy in Fe 2 B equal to 196.19 kJ mol −1 . Additionally, both models were checked out empirically by selecting three extra boronizing conditions obtained at 1273 K for increasing times (2.5, 4.5 and 8.5 h). The predicted layers’ thicknesses were found to be in line with the experimental results.

Notched structures in machine parts for several reasons cause discontinuity and stress concentration. It is essential to optimize these stress concentrations in notched parts. This study determined the best notch shape by creating different notch shapes by keeping two key points fixed on the spline curve in the notched region. This paper involves optimizing the shape of a fillet in a notched tension bar. An optimal shape was aimed to minimize the notch factor without causing yield anywhere in the bar by parametrically controlling the spline of the fillet via ANSYS parametric design language code. Optimal shapes of B-spline curves were obtained for round bars subject to axial tension loadings. Changing the code can also be used for bending or combined loading conditions other than tensile loading.

Machining is one of the most precise manufacturing methods used in the manufacturing of machine parts. In machining, significant tool wear is observed due to cutting tool-to-workpiece contact. Controlling tool wear and minimizing the effect of tool wear in this method is an important research topic. In this study, machinability tests were carried out on AISI 4462 duplex stainless steel materials, which are in the hard-to-cut material class. In the experiments, the changes in tool life and surface roughness were analyzed by using 150, 180, and 210 m/min cutting speeds; 0.1 mm feed; and 0.8 mm depth of cut. Increasing cutting speed significantly increased wear and reduced tool life. However, experiments with cutting speeds of 180 m/min and 210 m/min had the same tool life values. In addition, significant notch wear and BUE formation were observed on the tool surface. Besides, it was determined that the surface roughness deteriorated due to tool wear. In addition, surface deterioration due to chip wrapping was also observed in many passes.

Due to the philosophy of the process, the surface roughness is usually high for the parts produced with laser powder bed fusion (L-PBF) additive manufacturing (AM). Parts produced by this method need surface quality improvement processes for many applications. One of the methods used for this purpose is high speed machining (HSM). HSM is a modern manufacturing technique that offers several benefits, including improved productivity, enhanced product quality, and reduced production costs. In addition, HSM can improve the quality of finished products by reducing machining errors. In this study, samples produced with 316L powder in size of 10 × 10 × 5 mm using three different hatch spacings (60, 70, 80 µm) and building orientations (0°, 45°, 90°) were produced by L-PBF method, and HSM process was applied to these samples. In this context, the present study aimed to investigate the effects of porosity, microstructure and microhardness properties of 316L samples produced by L-PBF method using different hatch spacings and build orientations on cutting forces, surface roughness and burr formation in HSM. When the numerical values of the cutting forces were analyzed in both x and y directions, it was observed that the greatest cutting force occurred in the x direction. While the Fx force ranged from 6.23 to 9.35 N, the Fy force ranged from 4.88 to 8.27 N. It has been determined that as the build orientation increases at the same hatch spacing value, the cutting forces increase due to the increased porosity ratio.

The chemical and physical characterization of glass beads in different sizes with diameters 3 mm, 4 mm, 5 mm and 6 mm, respectively, have been studied in this paper. The X-ray Diffraction (XRD) analysis exhibited that the structure of glass bead is amorphous, and the diffraction peaks for annealing sample 400 °C and 600 °C, respectively, are seen at 2 θ values ranged (26.165°–29.47°). The Scanning Electron Microscopy (SEM) and chemical composition measurement by Energy Dispersive Spectrometer (EDS) system have been conducted; they exhibited that all the samples have the same smooth surface, and the chemical composition analysis showed that the weight percentage of oxygen and silicon were dominant elements in the main structure of glass beads as well as some other elements like Ca, Mg, and Na were observed.

Polyurethane is a versatile polymer with a high degree of toughness and ductility used in a wide variety of applications. In this study, two-part thermoset polyurethane was used as a matrix material to prepare hybrid and non-hybrid composites. Hybrid laminates were prepared by combining either glass fiber or basalt fibers with steel fibers. The mechanical properties of prepared composite specimens were characterized and scanning electron microscope (SEM) observation was performed around the fracture region of the tested specimens. The results revealed a significant increment in tensile strength, and flexural strength in BS 1 -PU (8 layers of basalt-1 layer of steel) hybrid laminate by 357.74 % and 64.59 %, respectively, compared to steel fibers reinforced polyurethane composites. Furthermore, GS 4 -PU hybrid composite (5 layers of glass-4 layers of steel) achieved an improvement in tensile strain by 12.07 %, flexural strain by 25.32 %, and absorbed energy by 18.21 %, compared to glass fibers reinforced polyurethane composite. Moreover, the SEM observations revealed that the replacement of some basalt and glass layers with steel layers leads to a positive hybridization effect of the overall produced hybrid composites.

The disc under diametral compression is one of the preferred specimens for the calibration of photoelastic materials. Current calibration methods have some limitations from a metrological point of view, because they do not provide measurement uncertainties and they assume that observations are independent and with the same accuracy. In this work, a new calibration method is proposed to avoid the above-mentioned metrological limitations: The generalized least squares by Lagrange multipliers method. This methodology accepts correlated input quantities or with different accuracy through the input covariance matrix, and it provides, through a least-squares adjustment, the estimates of the quantities to be measured and their associated standard uncertainties. The application of the method shows coherent results and it also provides a chi-square value that can be used to test the consistency of the measurement model, and the normalized deviations between the input estimates and their fitted values, which are a tool to identify potential outliers. Results reveal a great influence of the radius of the specimen on the uncertainty of the stress-optic coefficient measurement, which casts serious doubt on previous affirmations about the disc in compression is preferable over other specimens.