Deposition of DLC/oxynitriding Films onto JIS SKD11 Steel by Bipolar-pulsed PECVD

Traditionally, JIS SKD11 tool steel is corresponding to the AISI D2. Since this material possesses high hardness and excellent wear resistance, it is usually used as a mold material and cutting tools.1,2) In order to improve the tool life, many studies have focused on surface treatment as a method of protecting the internal material.2) Nitriding is a thermo-chemical process with nitrogen diffusion, which leads to increase the surface hardness of the treated steels. It reveals an effective improvement of thermal fatigue characteristics due to the effects of compressive stress and the hardened surface.3) In addition, oxynitriding processes use air or steam at the end of the nitriding stage; used as an oxidizing medium, they are an integral part of the treatment. Generally, the oxynitriding process can form several kinds of nitride (Fe2N, Fe3N and Fe4N) and oxides (Fe2O3 and Fe3O4). Especially, the Fe3O4 layer of oxidation treatment can effectively protect and improve the erosion and corrosion resistance of steels.4,5) Diamond-like carbon (DLC) films are metastable amorphous carbon (sp3 and sp2 bonds) materials with superior tribological characteristics.6) The high hardness, low friction coefficient and chemical resistance of the DLC films make them good candidates as protective coatings for metal, steels and optical or electronic components.7) Recently, direct curDeposition of DLC/oxynitriding Films onto JIS SKD11 Steel by Bipolar-pulsed PECVD