High Strength HIPRBSN - An Optimization by Statistical Methods

Abstract

Because of the high content of the beta modification in sintering additive containing RBSN it was assumed that this typ of Si₃N₄ cannot be densified by sintering or HIP to a high strength material. By using statistical methods it could be shown however that the homogeneity of the microstructure - regardless of the beta content - is the most important strength controlling factor. By carrying out 32 Taguchi tests, 2048 experiments have been simulated concerning the influence of the starting silicon powder, the typ and concentration of additives and the preparation parameters on the microstructure and the resulting mechanical strength. By combining the optimum processing parameters Weibull moduli sigma of about 1000 MPa and m of about 30 could be achieved in 4-point bend ^°testing in HIPRBSN with beta contents of about 50 percent in the starting RBSN material.