Microstructure and Properties of Al–Ni Intermetallic Compound Coatings Prepared by Cold Spraying

Ni–Al intermetallic compounds (IMCs) attract considerable attention for their low density, high melting point, and excellent acid‐alkali corrosion resistance—NiAl 3 shows favorable tribological properties, while Ni 2 Al 3 has outstanding high‐temperature oxidation and corrosion resistance. As an emerging additive manufacturing technology, cold spraying features low heat input, no oxidation, and no phase transformation, making it ideal for coating preparation. In this study, specimens were prepared via low‐pressure cold spraying combined with diffusion heat treatment. X‐ray diffraction, scanning electron microscope energy dispersive X‐ray spectroscopy, ImageJ software, and a Vickers hardness tester were used to analyze phase composition, microstructural morphology, porosity, and microhardness, as well as to explore their evolution with phase transformation time and diffusion kinetics characteristics. Results show that after 500°C heat treatment for 1–5 h, porosity first rose, then fell. NiAl 3 formed preferentially at 0–1 h; from 1–2 h, Ni 2 Al 3 content increased with porosity due to the Kirkendall effect, peaking at 5 h. Both phases formed synchronously at the initial stage of 550°C heat treatment, with maximum hardness reaching 284.04 HV 0 .5 . This study provides theoretical and experimental references for optimizing high‐performance Ni–Al intermetallic compound coating preparation via cold spraying.