Investigation of surface properties of TiN and CrN coatings on nitrided SKD61 steel using duplex surface treatment technology

Abstract

In this study, CrN and TiN hard thin films were deposited on nitrided SKD61 steel or heat-treated substrates using the cathodic arc plasma evaporation method. The microstructure and surface properties of thin films were investigated by optical microscope, stereo microscope, microhardness test, adhesion test by Verein Deutscher Ingenieure (VDI) 3198 standard, and abrasion test. The microstructure of the duplex-treated surface layer consists of a thin CrN or TiN coating with a thickness of about 2 µm on a nitrided SKD61 steel substrate (~90 µm). The adhesion of CrN and TiN films on the nitrided substrate was enhanced compared to the adhesion of the coatings deposited on the heat-treated steel substrate. The adhesion of CrN and TiN coatings on heat-treated steel substrates only reached HF6, while the adhesion of the corresponding coatings on N-impregnated steel substrates reached HF2-HF3. The surface hardness and wear resistance of the steel were improved by the simultaneous processing of cathodic arc plasma deposition and nitriding technology. The surface of thin film TiN coated on N-treated steel substrates has the best hardness and wear resistance. It is noteworthy that TiN coating exhibits higher surface hardness and wear resistance than CrN coating.