Microstructural Transformation and High-Temperature Aluminum Corrosion Properties of Co-Based Alloy Coating Prepared by Laser Cladding

A Co-based alloy coating was deposited on H13 steel substrate via pulsed Nd:YAG laser and the corrosion resistance to and mechanism of corrosion in molten aluminum were explored. The results showed that the coating was mainly composed of gamma-Co dendrite and M23C6 precipitation. The average hardness in the cladding layer was 732.6 HV0.5, which was 3.55 times greater than that of the H13 substrate. During the molten aluminum corrosion test, the surface of the Co-based alloy coating was immersed for 4, 8, 16 and 24 h at 700 degrees C. The corrosion rate decreased with increases in aluminum erosion time. It was observed that there were two intermediate layers between the coating and the liquid Al, with (Co, Fe, Cr)(2)Al-9 intermetallic compounds (IMCs) layer near the coating side and the (Fe, Cr)(4)Al-13 and (Co, Fe, Cr)(2)Al-5 intermetallic compounds (IMCs) layer near the Al solidification side. After 24 h of static corrosion, the Co-based alloy coating could still maintain its integrity to protect the substrate.