Thermomechanical behaviour of WC-W2C composites at first wall in fusion conditions

Abstract

Metallic tungsten and tungsten carbide are some of the more relevant candidates proposed because of their high melting point, shielding capabilities and resistance to neutron damage. In this work, the microstructural and high temperature mechanical characterization of WC matrices with additions of 10, 20 and 50 vol% of W, dispersed by colloidal processing routes and sintered by Spark Plasma Sintering (SPS), are presented. Flexural elastic modulus, fracture strength and SENB toughness has been determined by the three-point bending tests at 600, 800, 1000 and 1200 °C.Microstructural analysis shows that after SPS all the metallic tungsten has reacted to form W2C, and sintering process is able to stabilize phases corresponding to temperatures higher than achieved as a consequence of the additional energy provided by the method. Mechanical results indicated that resistance of all materials increases as the operating temperature increases. Furthermore, remarkably great results are obtained for the composition with 10 and 20 vol% of W. This macroscopic behaviour has been related to the microstructural decomposition of the metastable W2C, to WC and W, as temperature for the bending tests approach to the equilibrium temperature (1250 °C). It was found that the presence of metallic tungsten in the final microstructure could be the responsible of the plastic behaviour of the tested pieces at 1200 °C and the doubled value of the toughness.