Structure and Properties of the Surface Layer of a Wear-Resistant Coating on Martensitic Steel after Electron-Beam Processing

Abstract

The paper reports electro-contact welding on Hardox 450 steel with С-V-Cr-Nb-W flux-cored wire. Supplementary irradiation by intense pulsed electron beam was carried out to improve mechanical properties. Micro-and nanohardness, Young modulus and tribological parameters of the modified surface were tested mechanically. It is pointed at the significant increase in the friction coefficient because the surface layer fractures and particles of the surfaced layer are involved in the process of friction. Using the methods of optical and scanning microscopy a great number of micro-pores were detected both on the irradiated surface and through the surfaced layer modified by intense pulsed electron beam. It is demonstrated that electron-beam processing of the deposited layer surface is the reason for occurrence of multi-layer structure. According to measurements it was determined that the modified (surface and transition) layers are 0.3 to 0.5 μm on overage. It was also found out that irradiation of the surfaced metal leads to significant refining of structural elements because of ultrahigh speeds of crystallization and further cooling down of the modified layer. The phase composition of the surfaced metal modified by pulsed electron beam is explored. Niobium carbide (NbC) is reported to form in the surface layer.