ESTIMATION OF THERMAL RESIDUAL STRESSES IN THIN COBALT BOND LAYERS OF THE WC–Cо HARDMETAL

Abstract

The task of the scientific study is to estimate the level of thermal residual stresses in the thin layers of the binding phase, and the carbide grains it surrounds, in alloys WC-Co. For this purpose, analytical methods, taking into account the stereometric parameters of the microstructure of the industrial marks of hardmetals, are defined in the plane section. It was established that the tensile stresses in thin cobalt layers for WC-4 wt% Co to WC-25 wt % Co alloys are 1350-1103 MPa and are lower than the average stresses in the bundle volume. Carbide grains in alloys WC-4 wt % Co  to WC-15 wt % Co are under the influence of tensile stresses, and WC-20 wt %Co and WC-25 wt %Co are compressive stresses, their level is much lower than in polycrystalline aggregates of carbide grains.  The application of the proposed method will allow monitoring the accuracy of the measurement of residual thermal stresses, will help to determine the optimal structure and technological cooling mode after sintering. Reducing local thermal stresses in alloys WC-Co will improve their strength, fracture toughness, wear resistance.