Surface phenomena in a precipitation-hardenable nickel–chromium alloy during multiple heating/cooling

Time-of-flight secondary ion mass spectrometry profiling, scanning transmission electron microscopy, and energy dispersive X-ray mapping were used to investigate physical and chemical processes on the surface of a precipitation-hardenable nickel–chromium alloy associated with single or multiple heating/cooling cycles that simulate typical service conditions of aircraft products made of such alloys. Research findings show the growth of oxide, increase of surface roughness, and microstructural changes. The depth distribution of main metal oxides is discussed. It was determined that aluminum diffusing along the alloy grain boundaries forms an oxide on the surface and intergranular Al₂O₃. The Ti and Nb nitride inclusions were found to appear after the first oxidation cycle. - Highlights: • Multiple heating/cooling cycles increase oxide thickness and surface roughness. • The microstructure changes under multiple heating/cooling. • Metal distribution in the oxide is formed mainly after the first heating/cooling. • Ti and Nb nitride inclusions were found in the oxide layer.