Microwave plasma etching of SS304 substrates for improved PVD coating adhesion

Fabricating microstructures on a substrate surface enhances surface roughness, improving the adhesion of physical vapor deposition (PVD) coatings. Currently, plasma etching is widely used to improve substrate surface roughness. However, it suffers from limitations such as low etching efficiency and substrate damage. This study explores microwave plasma etching as an innovative approach to enhance surface roughness, combined with magnetron sputtering to improve coating adhesion. The effects of etching time on substrate morphology, roughness, and wettability are systematically analyzed, along with their influence on chromium (Cr) coating properties. Results show that microwave plasma etching increases surface roughness and wettability without altering the substrate’s phase structure. The crystallographic orientation of Cr coatings is less affected by the substrate surface roughness. Indentation and scratch tests are conducted to evaluate the adhesion strength under dynamic and static conditions. When the etching time is 2 h and the substrate surface roughness is 10.5 nm, the adhesion strength between the coating and the substrate reaches a maximum of 42.7 N, which is nearly a 100 % improvement compared to the adhesion strength of the polished substrate. This study demonstrates an effective method for improving substrate roughness and provides insights into enhancing the coating adhesion.