Test method for coarse-grained tungsten alloy samples for creep under compression deformation

A method for studying the deformation mechanism in the creep mode during compression tests of industrial tungsten alloy samples is proposed. The tests are performed using a Dr. Sinter model SPS-625 vacuum spark plasma sintering unit. Compression tests are performed on cylindrical samples placed between two punches; the sample is heated by radiation heating from a graphite mold with a diameter greater than that of the sample. The temperature is controlled using an optical pyrometer focused on the surface of the graphite mold through which high-power millisecond current pulses are passed. Sample deformation is controlled using a dilatometer included in the Dr. Sinter model SPS-625 unit. Before testing, the temperature dependence of sample shrinkage is studied in the heating mode at a given rate. Creep tests are carried out in two modes: (i) isothermal holding at different temperatures (975 – 1050 °C) at a given stress (50 MPa), which allows estimating the creep activation energy; (ii) stress jump tests at a fixed temperature (975 °C), which allow estimating the coefficient n in the power creep equation. The activation energy of creep activation energy for tungsten alloy (~ 18 – 19 kTm) and the coefficient n in the power creep equation (n ~ 2.3) are determined. The calculated parameters of the creep equation correspond to the case of sliding and climb of lattice dislocations in a field of uniformly spaced point obstacles. The microstructure and microhardness of the samples after creep tests at different temperatures are studied.