Features of oxidation of copper-nickel alloys synthesized by spark plasma sintering

Abstract

Data on high-temperature tests for heat resistance of copper-nickel-based powder materials synthesized by spark plasma sintering (SPS) are presents. The features of oxidation of copper-nickel alloys with various alloying elements at temperatures above 1000 °C have been studied. Based on the research results, the dependence of the growth rate of the oxide film on the high-temperature oxidation temperature was established, and the influence of alloying elements in the composition of sintered copper-nickel alloys on their heat resistance was considered. It is shown that the highest heat resistance is provided by alloying copper-nickel alloys with aluminum and chromium. For all considered compositions of copper-nickel alloys synthesized by spark plasma sintering, the temperature point of 1100 °C during a 20-hour heat resistance test is the limiting one, since most of the samples are completely destroyed. The scale growth rate for composition Cu – Ni – Cr – Al 1.49·10–3 g/cm3 is lower than the oxidation rate of pure nickel 3.78·10–3 g/cm3 at 1000 °C and these two samples demonstrate the lowest weight gain after testing at 1000 °С. For compositions Cu – Ni, Cu – Ni – Cr – C(graphite) and Cu – Ni – Al the oxidation rate increases by two orders of magnitude, for compositions Cu – Ni – Cr and Cu – Ni – Cr – Si — by three orders of magnitude. Despite increase of test temperature up to 1100 °C, the rate of scale growth on the surface of Cu – Ni – Cr and Cu – Ni – Al specimens remain practically unchanged: 124.01·10–3 and 210.43·10–3 g/cm3 at 1000 °C; 153.44·10–3 and 203.87·10–3 g/cm3 at 1100 °C. Deceleration of the oxidation kinetics of these samples with temperature increase is ensured by formation of oxide film on the surface, which has a dense structure with good adhesion to the basic material.