Heat treatment of thermal spray duplex coating system of aluminum - nickel chromium alloy on carbon steel

摘要

This paper presents our study on the influence of heat treatment at 550°C on the microstructure and microhardness of Al-NiCr20 duplex coating prepared on low carbon steel by electric-arc thermal spray. The annealing duration was in the range of 2-8 hours. The obtained results showed that after annealing, metallic grains inside the coatings became flatter and the coating's porosity decreased considerably. The formed phases and distribution of elements in the coatings was analysed by SEM-EDX method, simultaneously microstructural observation by optical microscope also showed a formation of two diffusion layers at both the interfaces "NiCr20-Al" and "Al-steel" with very high microhardness values (> 900 HV). Based on the chemical composition obtained by SEM-EDX, the chemical formulae of the formed intermetallic compounds were proposed.