Effect of plasma-assisted laser pretreatment of hard coatings surface on the physical and chemical bonding between PVD soft and hard coatings and its resulting properties

This research reveals for the first time, how different surface pretreatments (including mechanical polishing, plasma etching, femtosecond laser texturing, and plasma-assisted femtosecond laser texturing) on the PVD hard coatings impact the physical and chemical bonding between PVD soft and hard coatings and its resulting properties. Therefore, the as-deposited TiAlN coatings were served as substrates for the following pretreatments and the deposition of WS2 soft coatings. The scratch tests and dry wear tests were carried out to investigate the adhesion and tribological performance of these WS2/TiAlN soft/hard composite coated samples. Results show that uniform and periodic nano-textures are fabricated on the TiAlN coatings surface by the plasma-assisted laser texturing, which results in high compressive stress and increased surface activity. Thus, the critical load of WS2 coatings deposited on the plasma-assisted laser textured TiAlN substrates (F-N = 46 N) exhibits higher values in comparison with the WS2 coatings deposited on untreated TiAlN substrate (F-N = 28 N). And, an obviously increasing in wear life of WS2 coatings from 2400 s to 5200 s is achieved by plasma-assisted laser texturing. Additionally, the growth mode of WS2 coatings deposited on the plasma-assisted laser pretreated TiAlN substrare is changed from Volmer-Weber model to Stranski-Krastanov model.