Microstructures of binary Cr–xNi alloys (0 ≤ Ni ≤ 50 wt.%) in their as-cast state and after high temperature exposure

Abstract

Metallic materials designed for use at very high temperature must be based on elements with high melting points. In this work, several binary alloys, chosen in the Cr-rich part of the Cr–Ni diagram, were elaborated by foundry and characterised by metallography in the as-cast condition and after exposure at 1200 °C. Many of the obtained alloys are composed of imbricated body-centred cubic chromium phase saturated in Ni and face-centred cubic nickel phase saturated in Cr. These structures may evolve more or less at high temperature. High values of hardness were obtained for some of these alloys, suggesting high strength at elevated temperature. The hardness evolution vs. the Cr content was well represented by a law of mixture of the volume fractions and the hardness of the separated phases. Already intrinsically resistant to oxidation at high temperature, most alloys are also not sensitive to internal nitridation, contrary to pure Cr. Such Cr–Ni alloys may be considered as possible bases for heat-resistant alloys.