Stellite coating deposited by directED energy deposition

Abstract

This paper explores a protective stellite coating on 1.4922 martensitic steel. Stellite coatings are often used to improve the properties of the part’s surface. The microstructure of the sample was analysed and its hardness measured. Protective coatings enhance mechanical and corrosion properties of the substrate, and thus extend the life of the respective part. They can be created by galvanizing, ion implantation, thermal spraying, or by more recent methods, such as laser cladding, DED (directed energy deposition) and others. DED is one of the metal deposition processes that fall in the AM category (additive manufacturing). It was used to deposit the protective coating in the present study. DED is an evolving technology which is suitable not only for prototype development, but also for promising applications involving surface treatment and repairs of functional parts. DED uses a laser beam as a thermal source to melt powder which is blown concentrically with the laser beam and the protective gas. The unique advantage of this method is a very good cohesion and bonding between the substrate and the deposited layer with a smaller HAZ (heat-affected zone). It produces comparatively few inhomogeneities and defects, which makes it a promising technique for protective layer applications. Stellite was chosen as a protective coating material because this group of alloys exhibits excellent properties such as high wear resistance, abrasion resistance, superior corrosion resistance and erosion resistance. These are relevant in many industrial sectors, such as power generation, aerospace and others. Stellite 21 was used in the present study.