Thermal properties of spark plasma sintered Inconel 625 modified by titanium zirconium mixed carbide

Nickel-based superalloys are an important group of advanced engineering materials used for high-temperature and/or corrosive environments. Lately, in order to improve their mechanical properties, carbide reinforcement is added to a metal matrix, creating composites of improved hardness, shear resistance, or tensile resistance. In order to preserve the wide applicability of those materials, thermal properties, and corrosion resistance must also be evaluated. Presented research evaluated the thermal properties of Inconel 625—(Ti,Zr)C0.85 composites obtained at 1000 °C by spark plasma sintering process. Sinters containing 5–20 mass% of carbide phases were initially characterized in terms of their density, phase composition, and microstructure. A thorough examination of their thermal properties included: dilatometry, laser flash analysis, and differential scanning calorimetry. Conducted experiments revealed that a growing amount of carbide reinforcement decreased the thermal diffusivity and conductivity of samples. Other materials had a nonlinear correlation with that parameter. Performed analysis allowed to make an initial evaluation of oxidation resistance at 800 °C. It was shown that above 5 mass% addition of (Ti,Zr)C0.85 there is a considerable mass gain change shown by samples during the first hour of oxidation before passive layers were created. Suitable chemical reactions were predicted in order to describe the oxidation process of obtained composites.