Microabrasive wear behavior of different stellites obtained by laser cladding and casting processes

Abstract

Cobalt superalloys are used in several applications, mainly involving corrosive environments and high temperatures, in which wear and corrosion resistance are key factors in their performance. These alloys can be produced by a variety of manufacturing processes. Among these, the technology of laser cladding coatings has emerged as a promising and economically viable alternative to produce coatings from cobalt-based alloys. One of the applications of these alloys is in the production of components to obtain second-generation ethanol. In this application, about 8% of the processed material is composed of micrometric abrasive particles, mainly silica, among others, which cause wear of components. In order to better understand the tribological behavior of these alloys in microabrasion, three coatings of commercial cobalt-based superalloys, Stellite 1, 6 and 12, were produced by laser cladding. Additionally, two cast alloys, Stellite 250 and an experimental Stellite alloy, were also evaluated. Microabrasion tests using a statistical design of experiments were performed with SiO2, Al2O3 and SiC abrasives in a suspension of distilled water. Statistical analysis revealed that the wear coefficients of these alloys are influenced by both the abrasives and the alloy. The as-cast Stellite 250 alloy showed the highest wear coefficients, while the coated Stellite 1 and the as-cast experimental Stellite showed the lowest wear coefficients. The predominant wear micromechanism was scratching, except for Stellite 6 and 12 coated alloys in SiC tests, in which predominant mechanism were mixed and rolling, respectively. The presence of secondary micromechanism of rolling wear was also observed and associated with the granulometric distribution of the abrasives. The analysis of wear severity allowed the comprehension of the granulometric distribution influence of abrasive particles on wear.