Cobalt based alloy PTA hardfacing on different substrate steels

Abstract

Components from equipment for different processing industries are exposed to severe service conditions. Parts are therefore manufactured so that specific demands can be met through adequate selection of surface processing techniques and hardfacing alloys. Whenever surface welding techniques are used to improve a component's performance, quality requirements such as controlled dilution of the deposited alloy by the substrate are a priority. This work has evaluated this interaction between a hardfacing Co based alloy and the substrate steel. A high carbon cobalt based alloy was ‘plasma transferred arc’ (PTA) deposited on three different substrate steels. The role of the chemical composition of the substrate on the characteristics of the coatings was evaluated for two sets of processing parameters, targeting two extreme dilution levels. Coatings characterisation was assessed through microstructure analysis, microhardness measurements, dilution levels, and wear rate measurements. Results showed that the influence of the substrate chemical composition was more significant for coatings of controlled low dilution deposits. The selection of the substrate steel affected dilution levels, microstructure, hardness values, and sliding wear rates exhibited by the coatings. On both sets of coatings deposits made on carbon steel gave better wear performance than those deposited on the stainless steels tested.