Preparation and Study of Ni–Al–O System Cermet Composites with a Small Addition of MgAl2O4 Nanoparticles

This paper presents the results of obtaining and studying the structure and properties of cermets based on powders of aluminum oxide and nickel–aluminum alloy doped with 0.1 wt % of aluminum–magnesium spinel nanoparticles sintered by the electrospark method on a FCT-HP D 25 unit in argon at t = 1470°C for 30 min. The results of the NiAl–65Al2O3 charge TG and DSC analysis at up to 1300°C are presented. It is found that the MgAl2O4 spinel in the form of individual nanoparticles (60 nm) or aggregates (less than 700 nm) are present along the grain boundaries of the composite. Internal friction studies at t = 20–900°C and high-temperature X-ray phase analysis at t = 700, 800, and 900°C were carried out to describe the degradation mechanisms of the strength properties of the materials. The effect of nanoparticles on the internal friction of the composite within Δt = 20–900°C in the NiAl–65Al2O3–0.1MgAl2O4 system is shown. Potential mechanisms for cermet strength-property degradation with increasing temperature are discussed. It is suggested that the appearance of extrema on internal friction curves at high temperatures can be caused by shifted phase boundaries of intermetallic compounds and the oxide component due to different coefficients of thermal expansion (CTE). A positive effect of doping with spinel nanoparticles on the short-term heat resistance of cermets at t = 750°C is found. The study of short-term heat resistance at t = 750°C shows that the sample with nanoparticles is more stable than the unmodified sample, which can be associated with the influence of interfacial hardening zones formed around nanoparticles according to the Obraztsov–Lurie–Belov theory and a number of studies carried out on metal matrices.