Structural and Phase Composition and Wear Mechanisms of Plasmasprayed NiCrSiB-20 wt.% TiB₂ Coating

Abstract

The structural and phase composition and wear mechanisms of the plasma-sprayed NKhTB20 coating (NiCrSiB–20 wt.% TiB₂) are studied. To produce the NKhTB20 composite coating, the commercial PR-NKh16SR3 powder was mixed with 20 wt.% TiB₂ and the charge was pressed and sintered in vacuum at 1100 °C for 30 min. The system components chemically interact in the sintering processes to from chromium borides. The sinters were ground and classified into the powder fraction –100+60 nm for plasma spraying. The plasma-sprayed NKhTB20 coating consists of a nickel-based matrix strengthened 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. 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.