Investigation of the effect of SiC content on the microstructure, physical properties and hardness of SiC/Ni composites

Abstract

Nickel matrix composites reinforced with alpha-silicon carbide of various concentrations (up to 4 wt.%) were investigated. Samples were made by powder mixing followed by a process of powder technology. The resulting SiC/nickel composite powders were cold compacted at 400 MPa in a single-axis head, followed by sintering in a controlled furnace at 1000 °C in an atmosphere of sintering a hydrogen/nitrogen mixture of 3:2. The SiC/Ni powders, as well as crushed and polished consolidated composites were investigated using a scanning electron microscope and X-ray diffraction (XRD). The microstructures of the obtained sintered SiC/Ni composites show a uniform distribution of SiC particles in the nickel matrix. XRD data showed that the sintered SiC/Ni composites consist mainly of (fcc) Ni as the main phase and α-SiC phase. To assess the sintering process of the obtained SiC/Ni composites, their density, electrical conductivity, coefficient of thermal expansion at various temperatures, and hardness were measured. The relative density, electrical conductivity, and thermal expansion coefficient of the sintered SiC/Ni composites obtained decreased; hardness increased by increasing the SiC content in the nickel matrix.