CVD Multiple-Layer Coatings on 9Cr18 Steel and Its Application for High-Precision Ball Bearings

Abstract

The process, microstructure and mechanical properties of the chemical vapor deposition (CVD) multiple-layer coatings titanium carbide, titanium carbonitride, and titanium nitride (TiC,TiCN,TiN) on 9Crl8 (1%°C, 18%°C) steel were investigated, and the process has been successfully applied to high-precision bearings. The results indicate that CVD multiple-layer coating has fine-grained microstructure and good adhesion, i.e., the bond strength to substrate. CVD multiple-layer-coated 9Crl8 steel has good properties of friction-wear resistance and high rolling contact fatigue life. The coating follows perfectly the substrate deformation at the compressive load testing, and its bearing load capacity depends on the strength of substrate. After CVD-coated 9Crl8 steel balls were lapped in batches, their surface roughness was noticeably improved. The performances of the high-precision bearings with CVD-coated balls increased significantly. After 1000 h operation, no trace of wear on the CVD-coated balls and uncoated bearing races was observed.