Fabrication processing and mechanical properties of Si3N4 ceramic turbocharger wheel

A composite technique was chosen to fabricate Si3N4 ceramic turbine wheel based on modified investment casting (MIC), slip casting (SP) and mold constraint hot isostatic pressing (MCHIP) aided by a near-net dimension using the gypsum mold and multi-piece Y2O3 ceramic mold. The detailed fabrication processing of Si3N4 ceramic turbine wheel was described. And the flexural strength and fracture toughness after different work temperature and speed were discussed. The results showed that owing to occurrence of phase transformation and chemical reaction, excess temperature resulted in interface cracking and interface debonding, flexural strength and fracture toughness decrease. Thermal expansion and centrifugal force under excessive high speed brought many pores in the microstructure and resulted in crack initiation and crack propagation. The critical work temperature was 700 °C and critical work speed was 100,000 r/min, which were obtained from the test and simulation results.