The effect of gas atmosphere on the coating formation by electric arc surfacing with cermet SHS electrodes of the TiB2–Co2B composition

Abstract

Due to their unique properties, metal-matrix composite materials, when used as a surfacing material for electric arc surfacing, provide high properties of the deposited layers. SHS-extrusion is a promising method for a wide range of surfacing metal-matrix electrodes. The gas environment of surfacing affects the quality of coatings formed by SHS electrodes, their microstructure and properties. In this paper, cermet SHS electrodes of the TiB2–Co2B composition obtained by SHS-extrusion were used to form protective coatings on a steel substrate by electric arc surfacing in an argon atmosphere and in a nitrogen atmosphere. The elemental and phase composition, as well as the microstructure of the deposited layers, were investigated. Based on the conducted studies, the influence of the gas atmosphere on the formation of the structure of cermet coatings was established. It is shown that, despite the similar phase composition, there are fundamental differences in the microstructures of the deposited coatings, which are caused by the partial fusion of the tungsten electrode and the transfer of the electrode material in the coating during surfacing in an argon atmosphere. The maximum values of the microhardness of coatings deposited in a nitrogen atmosphere exceed the maximum microhardness of coatings obtained by surfacing in an argon atmosphere by 200–450 HV.