Rong Liu, Yinping Ding and Kafeel Kamal
Superalloys display exceptional performance in resisting severe wear and corrosion as well as high-temperature degradation. This paper presents a study on 700 Series Stellite alloys, which are cobalt-based superalloys containing high carbon content (> 1 wt.%) with different levels of molybdenum between 5 wt.% and 18 wt.%. The microstructure, hardness, wear and corrosion resistance, of three 700 series Stellite alloys are investigated using scanning electron microscopy (SEM), X ray diffraction (XRD), a Rockwell hardness tester, a pin-on-disc tribometer, and immersion and electrochemical methods, respectively. It is shown that these alloys exhibit high hardness and excellent wear resistance. Both carbon and molybdenum contents influence the microstructure of these alloys significantly. The former determines the volume fraction of carbides precipitated in the alloys and the latter governs the amount of Mo-rich carbides and intermetallic compounds formed in the alloys. In the severe corrosive medium – Green Death solution, 700 Series Stellite alloys perform superbly owing to the ability of forming protective oxide film and retaining it on the alloy surface due to high chromium and molybdenum contents.
Stellite alloy; Molybdenum;Microstructure; Wear; Corrosion