Pulse Plasma Nitriding For Plasma Vapour Deposition Coating of High Speed Steels

Abstract

Hard physical vapour deposition (PVD) coatings have extremely desirable properties, tailored to the needs of industrial applications, but sometimes have inadequate frictional properties and frequently fail owing to inadequate support from the steel substrate. Cutting tools are subjected to high subsurface shear stresses and sliding abrasion. Coatings require maximum adhesion onto the substrate and reduced sliding friction and wear coefficients. Optimised pulse plasma nitriding of M2 high speed steel (HSS) prior to PVD processing provides support for the hard coatings and enhances wear resistance. The Eltropuls patented ignition pulse allows stable plasma, minimum heat input, maximum treatable surface, thermal uniformity and minimum energy costs. Pulse plasma nitriding provides optimum surface morphology and composition control within a nitrided case. The inherent high hardness of HSS allows a shallow case to be produced in short nitriding times. Good adhesion is ensured by suppressing compound layer formation. Drilling trials into a 15 mm thick plate of AISI 304 demonstrate that nitriding prior to deposition of TiAlN/VN or C/Cr superlattice PVD coatings significantly increases drill life. SE/502