WEAR-RESISTANCE OF PRENITRIDED HARDCOATED STEELS FOR TOOLS AND MACHINE COMPONENTS

Hardened and tempered low-ahoy steel 31CrMoV9 and the high-ahoy tool s teels S 6-5-2 and X155CrMoV121 were nitrided to form a varied structur e of the substrate for the subsequent hardcoating. The tool steels wer e nitrided and hardcoated in a continuous process in a modified commer cial PVD plant. The duplex treatment of the low-alloy steel was realiz ed by separate nitriding and hardcoating in different plants. The TiN and CrN were deposited with a thickness of approx. 3 mu m by hollow ca thode discharge evaporation. The composition and structure of the nitr ided case, the interstage treatment before deposition, as well as the deposition parameters influence the properties of the composite. The a dhesion can be improved essentially by prenitriding and deposition of a gradient interlayer system. The resistance of the tool steels to met al cutting and forming increases due to the production of an applicati on-specific duplex layer. The resistance to sliding wear and contact f atigue was investigated on various duplex-treated low-ahoy steel by ni triding the substrate. Whereas the nitrided case has a very high influ ence on the contact fatigue limit, the hardcoating reduces the wear by sliding and abrasion, which is of special interest for machine compon ents with higher slip.