Structural and Tribological Performance of Solid NiCr-WSe₂-BaF₂·CaF₂-Y-hBN and NiCr-WSe₂-BaF₂·CaF₂-Y Lubricant Coatings Produced by Atmospheric Plasma Spray

ABSTRACT

NiCr matrix WSe₂-BaF₂·CaF₂-Y-hBN and WSe₂-BaF₂·CaF₂-Y powders were prepared by mechanical granulation and crushing, and composite coatings were fabricated by atmospheric plasma spray technology. The microstructures and phase compositions of the powders, as well as the coatings, were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The friction coefficient and the wear behavior of the coatings from ambient temperature to 800°C were evaluated using a ball-on-disk tribometer. From the investigation of the worn surfaces, it was concluded that brittle fracture and delamination were the dominant wear mechanisms of the coatings at low temperature. At higher temperatures, a dense and protective oxide layer (BaCrO₄ and NiO) is generated on the worn surfaces of the coatings. Layered hexagonal BN particles reduce the direct contact and severe adhesion between friction pairs. Thus, the friction coefficient of the NiCr-WSe₂-BaF₂·CaF₂-Y-hBN coating is stable at the evaluated temperatures relative to the non-hBN coating. These fluorides exhibit excellent properties in these coatings over a large temperature range.

KEYWORDS:

• Solid lubricant coating
• tribology
• high temperature
• thermal spray coating
• sliding wear

Funding

The authors acknowledge financial support from the National Natural Science Foundation of China (NSFC) (Grant No. 51405497).