Microstructural study on ultra-high temperature erosion mechanism of infiltrated W-10 wt%Cu composite

It is tried in this paper to study microstructural features related to erosion of infiltrated W-10 wt%Cu at ultrahigh temperature against liquid alumina droplets. Also the effect of post-sintering annealing on the fracture mode and erosion resistance of the composite has been examined. For this purpose, the composite material has been prepared by compressing, sintering (also vacuum annealing) and infiltration of initial tungsten powder. The erosion test carried out by static firing of the bi-propellant engine (using two types of propellant: typically a fuel and an oxidizer) and the microstructure evolutions were studied by SEM and EDS. It is found that the main erosion mechanism of infiltrated W-10 wt%Cu composite, includes inter-granular fracture of tungsten skeleton and chipping. Extra sintering of skeleton takes place in outer copper-free skin of eroded composite. Also, melting and evaporation of copper occurs due to ultra-high temperature of erosion test and leads to formation of evacuated porosities. On the other hand, alumina droplets can penetrate into evacuated porosities. Also, vacuum annealing of sintered skeleton resulted into about 33% higher erosion resistance of composite. The obtained results were discussed based on weak points in infiltrated composite, transpiration cooling and microstructural evolution during erosion. This study provides an insight into correlating microstructural evolution with the erosion mechanism of infiltrated W-10 wt%Cu composite.