Tribological and dry drilling performance of WS2/Cr-AlCrN coatings

Abstract

Dry drilling gives a higher request to the anti-friction property of cutting tools. However, most tool coatings commonly have less lubricant effect. In present paper, WS2/Cr layer was deposited on AlCrN layer by a radio frequency magnetron sputtering system, forming the WS2/Cr-AlCrN lubricant-hard coatings. Its microstructure was studied using scanning electric microscope (SEM) and X-ray diffraction (XRD). Dry sliding tests were carried out against Ti6Al4V balls to evaluate the lubricant effect of the lubricant-hard coatings with different Cr contents in WS2/Cr layer. Dry drilling performance of WS2/Cr-AlCrN coating was also studied compared with uncoated and AlCrN coated tool in dry drilling of Ti6Al4V and 7075Al. It is found that as Cr contents increased, WS2/Cr became denser but the crystallinity decreased. The coating with Cr content of ~9.8 at.% had the best lubricant effect with the lowest friction coefficient and the narrowest wear track. Dry drilling tests show that WS2/Cr-AlCrN coated tool had the longest tool life and produced the lowest surface roughness. The high wear resistance of AlCrN layer was mainly played near cutting edge. While the anti-friction role of the lubricant layer was mainly played on drill flute, resulting in less material adhesion and improved chip removal.