Combined post-treatment approach for improving the surface integrity of CVD α-Al2O3 coating and the tool wear resistance

Abstract

Wet blasting effectively reduces roughness and introduces residual compressive stress on the chemical vapor deposition (CVD) coating surface; however, it possesses some limitations when the roughness exceeds a certain threshold due to the coating thickness reduction caused by wet blasting. In contrast, sprayed abrasives polishing (SAP) further reduces surface roughness but does not significantly alleviate tensile stress. To address these challenges, a composite process that combines wet blasting and SAP is employed for CVD post-treatment. This study aims to compare the effects of this composite process with those of wet-blasting and SAP processes in terms of surface morphology, surface roughness, physical structure, residual stress, adhesive strength between the coating and substrate, and cutting performance. Among different post-treatment methods, the composite process proves to be the most effective, resulting in superior surface roughness and morphology, similar residual compressive stress compared with the wet-blasting process, and strongest adhesive strength between the coating and substrate. This composite process achieves a smoother surface while maintaining the same level of residual compressive stress and preventing further significant thinning of the coating compared with the wet-blasting process. Finally, the composite process successfully enhanced the wear resistance of the CVD-coated inserts as demonstrated by cutting tests.