Wear resistance of prenitrided hardcoated steels for tools and machine components

Abstract

Hardened and tempered low-alloy steel 31CrMoV9 and the high-alloy tool steels S 6-5-2 and X155CrMoV121 were nitrided to form a varied structure of the substrate for the subsequent hardcoating. The tool steels were nitrided and hardcoated in a continuous process in a modified commercial PVD plant. The duplex treatment of the low-alloy steel was realized by separate nitriding and hardcoating in different plants. The TiN and CrN were deposited with a thickness of approx. 3 μm by hollow cathode discharge evaporation. The composition and structure of the nitrided case, the interstage treatment before deposition, as well as the deposition parameters influence the properties of the composite. The adhesion can be improved essentially by prenitriding and deposition of a gradient interlayer system. The resistance of the tool steels to metal cutting and forming increases due to the production of an application-specific duplex layer. The resistance to sliding wear and contact fatigue was investigated on various duplex-treated low-alloy steel by nitriding the substrate. Whereas the nitrided case has a very high influence on the contact fatigue limit, the hardcoating reduces the wear by sliding and abrasion, which is of special interest for machine components with higher slip.