STRUCTURE, PHASE COMPOSITION, AND WEAR MECHANISMS OF PLASMA-SPRAYED NiCrSiB–20 wt.% TiB2 COATING

Abstract

The structure, phase composition, and wear mechanisms of plasma-sprayed NKhTB20 coating (NiCrSiB–20 wt.% TiB2) are studied. To produce NKhTB20 composite powder, commercial PR-NKh16SR3 (NiCrSiB) powder was mixed with 20 wt.% TiB2 and the charge was pressed and sintered in vacuum at 1100C for 30 min. During sintering, the components react to form chromium borides. The sinters were ground and classified into the particle size fraction –100+60 nm for plasma spraying. The plasma-sprayed NKhTB20 coating consists of a nickel-based matrix reinforced with titanium diboride and chromium boride grains. The friction and wear behavior of the NKhTB20 coating in dry friction against plasma-sprayed NiCrSiB and NKhTB20 coatings is examined. It is revealed that the NKhTB20/NiCrSiB friction pair has higher wear resistance than NKhTB20/NKhTB20. The contact surfaces of the NKhTB20/NKhTB20 friction pair are damaged under oxidative and abrasive wear mechanisms. Oxidative wear is the dominant mechanism for the NKhTB20/NiCrSiB friction surface. Complex oxide films form on the NKhTB20/NiCrSiB sliding surface and prevent it from damage.