Characteristics and wear performance of borided AISI 440C matensitic stainless steel

In this study, some mechanical properties and diffusion kinetics of boride layer on AISI 440C matensitic stainless steel were investigated. Boriding treatment was conducted at temperatures of 1123, 1173, 1223 and 1323 K for 2, 4, 6 and 8 h by pack method. The boride layers were characterised by optical microscopy, X-ray diffraction (XRD), micro-Vickers hardness tester and Daimler-Benz Rockwell-C adhesion test. The boride layers produced on the AISI 440C matensitic stainless steel exhibited a smooth and regular morphology. Depending on treatment time and temperature, the boride layers had a thickness of 9.3 to 97.2 μm. XRD analysis revealed the existence of FeB, Fe₂B and CrB compounds. The hardness of the surface was increased from 393 to 1730–2080 HV_0.05 after the boriding process. The activation energy of layer was 203.723 kJ/mol. The adhesion strength quality of the layers depended on the dual-phase structure according to the VDI 3198 norm. Comparison of wear performance between boride coating and substrate showed that the coating can significantly improve wear resistance of the material. Friction coefficient decreased from the 0.41 to 0.32 and wear weight loss decreased by 82.97%.