Cavitation and Slurry Erosion Wear of Thermally Sprayed Hardmetal Coatings

Abstract

Thermally sprayed coatings are used to protect and provide life extension to components intended to perform in aggressive conditions such as extreme temperatures, wear and corrosive environments. In the present study two hardmetal compositions, Cr3C2-25NiCr and WC-10Co4Cr, were thermally sprayed with three different technologies: high-velocity oxygen fuel (HVOF) with gas or liquid fuel and high-velocity air fuel (HVAF) spray process. The samples were exposed to slurry and cavitation erosion conditions using a pin mill slurry pot unit and a vibratory apparatus, respectively. The slurry pot tests were performed with two different abrasive particle sizes. Besides the volume loss results obtained, SEM micrographs of the surface coatings were taken before and after the tests to study the erosion mechanisms. Regarding cavitation erosion, HVAF coatings were the best performing ones, followed by liquid fuel HVOF coatings. The same trend was observed for slurry erosion test results but with some exceptions, e.g. one of the HVAF coatings of Cr3C2-25NiCr presented bigger volume loss than the HVOF coatings. In addition, the liquid fuel HVOF sprayed coatings of WC-10Co4Cr were the worst performing in the test with coarse erodent particles.