Sliding wear of blended cobalt based alloys

This investigation reports on the tribomechanical evaluations of a Co-based alloy obtained by the hot isostatic pressing (HIPing) of a blend of two standard gas atomized cobalt alloy powders. A HIPed blend of Stellite 6 and Stellite 20 was used to investigate the effect of varying the C, Cr, and W content simultaneously on the structure-property relationships. Microstructural evaluations involved scanning electron microscopy and x-ray diffraction. Experimental evaluations were conducted using hardness, impact, tensile, abrasive wear and sliding wear tests to develop an understanding of the mechanical and tribological performance of the alloys. Results are discussed in terms of the failure modes for the mechanical tests, and wear mechanisms for the tribological tests. This study indicates that powder blends can be used to design for a desired combination of mechanical strength and wear properties in these HIPed alloys. Specific relationships were observed between the alloy composition and carbide content, hardness, impact energy and wear resistance. There was a linear relationship between the weighted W- and C-content and the carbide fraction. The abrasive wear performance also showed a linear relationship with the weighted alloy composition. The pin-on-disc and ball-on-flat experiments revealed a more complex relationship between the alloy composition and the wear rate.