Si3N4-based composites suitable for the production of complex shape by improved machinability

The effect of addition of 20vol% h-BN on the mechanical properties, surface finishing and machinability of a Si3N4-5vol% MoSi2 hot-pressed matrix was studied. After preparation of the specimens, the surface finishing of the BN-containing composite was much lower than the starting matrix. The introduction of BN phase remarkably reduced all the mechanical properties of the reference matrix. In the case of hardness and Young s modulus, the decrease measured in the composite was mainly due to the low hardness and Young s modulus for the BN phase. The materials machinability was quantitatively assessed by turning and drilling tests. In the severe turning tests, the wear resistance of the BNcontaining composite was three times lower than the starting matrix. In the mild drilling tests, the high machinability of the composite was clearly put in evidence as the reference matrix couldn t be drilled at all.