Volume 57, Issue 12

SS-309L and Inconel 625 are recommended buffer layers between nickel-based hardfacing and P91 steel to avoid crack formation due to the martensite formation in heat affected zone (HAZ). These buffer layers have different metallurgical characteristics and significant cost difference. Hence, this article attempts to identify suitable buffer layer between SS-309L and Inconel 625. These buffer layers are deposited independently on P91 steel using flux cored arc welding followed by metallurgical characterizations. Metallographic results confirmed the presence of γ austenitic phases and columnar dendrites in both buffer layers. Lower HAZ hardness was observed due to absence of cube-shaped precipitates and high dilution of iron in SS-309L compared to Inconel 625. Coupled with cost effectiveness and metallographic observations, SS-309L material emerges as candidate buffer layer between nickel-based hardfacing and P91 steel.

Gilded silver thread was used in the baroque era in the manufacture of sumptuous fabrics for princely garments as well as in the interior decoration of the Royal State Apartments. In this work, gilded silver threads from sumptuous fabrics from the era of Augustus the Strong (1670 – 1733) were studied with the aim of examining the microstructure and the chemical composition of the silver threads and the gilding. In addition, the metal threads were examined with regard to occurring corrosion phenomena as well as corrosion mechanisms.

Fatigue failure of a component can occur at service loads considerably lower than the yield strength of the material. Under fatigue loading condition, the material in the vicinity of the tip of a propagating crack repeatedly deforms plastically, leaving microscopic marks on the crack surface, commonly known as fatigue striations. Counting and measuring fatigue striations is a method in estimating the number of loading cycles a component went through until fracture. Some studies suggest a one-to-one relation between the number of fatigue striations and the number of load cycles, but this relation is still debatable, given that there are many factors influencing the formation of those striations. The main purpose of this work is to analyze the influence of microstructure and mechanical strength on the formation of fatigue striations in structural steels, in order to understand how these material properties are related to the fatigue crack behavior. For such, standard Charpy-V samples were subjected to hardness, fatigue and impact testing. Metallography was performed to characterize the microstructure, and a fractographic analysis by using optical and scanning electron microscopy was carried out to investigate the fracture surface. This study shows that steels with higher ductility have a closer one-to-one relation than those with a higher tensile strength. Above a certain level of tensile strength, fatigue striations do form rarely or completely disappear.