Quantitative Characterization of Microstructure of WC-Co/TiC-Al2O3 Composite Materials with Relate to Mechanical Properties.

Abstract

The microstructure of WC-Co/TiC-Al2O3 sintered composites has been characterized quantitatively by means of image analysis. The areal fraction, the grain size distribution and the uniformity of spatial distribution expressed by the void size distribution of each component have been correlated with the mechanical properties of samples such as Vickers hardness and transverse rupture strength under various sintering temperatures.The results revealed that the larger amount of WC dissolution and smaller grains were obtained at higher sintering temperature, while the total areal fraction of β-matrix formed increased to get higher hardness but lower strength. Further, at the higher temperature, the lower areal fraction of Al2O3 was obtained from densification of alumina aggregates due to the rearrangement of individual particles to yield lower composite strength.Void size distributions of total components were relatively uniform due to the high degree of mixing of powder achieved by means of Hybridizer™. Further, more uniform dispersions of WC and Al2O3 grains were obtained at low sintering temperature, while the TiC-WC phase was dispersed uniformly at the high temperature. Thus, the areal fraction and spatial uniformity of WC and Al2O3 components were most influential to the higher strength of composite, while the higher hardness was governed by those of the β -phase.