Influence of heat treatment on the structure and properties of the tungsten-containing coating of the working part of oil and gas equipment

Abstract

The influence of heat treatment modes on the structure and properties of the Ni – Cr – B – WC coating system applied by GDCS (cold flame spraying) on the working part of the Compressor Rod product of oil and gas equipment has been revealed. The optimal quenching mode for tungsten coating on AISI 4140 steel is recommended, including heating to temperatures of 1150 °C, exposure, followed by rapid cooling in a water-polymer medium. Using optical and scanning electron microscopy (SEM), the features of the formation of the structure and distribution of the carbide phase in the coating are determined. According to the structural analysis, after heat treatment, partial recrystallization of the binding components (Ni) occurs, redistribution of hardening particles (WC, Cr, B), which leads to a change in the structure and dispersion of the sprayed surface layer of the product. It is established that, depending on the parameters of heat treatment and further local remelting, an increase in interplate cohesion, a decrease in porosity, and a decrease in the microhardness of the coating base on average by 20 % of the initial value is observed, characteristic of this process. Recrystallization processes at the stage of heat treatment of the alloyed coating increase wear resistance despite a decrease in hardness. The achieved results make it possible to predict the possibility of using such products after heat treatment in a friction pair with increased requirements for wear resistance and adhesive strength.