High-speed laser-clad 3533-00 Fe-based cemented carbide coatings on nuclear power valve sealing surface to enhanced wear and corrosion resistance

Surfacing welding Co-based alloys coatings is often used to improve the wear and corrosion resistance of nuclear power valve sealing surface. The surfacing welding process, however, resulted in a number of defects, such as porosities, inclusions, and even cracks. Moreover, 59Co in wear and corrosion debris in a radioactive environment can form 60Co, which can lead to nuclear contamination and higher maintenance costs. To tackle this issue, high-speed laser cladding technique has been employed to obtain 3533-00 Fe-based cemented carbide coatings on nuclear power valve sealing surface. According to the SEM, XRD, EPMA and EBSD results, 3533-00 Fe-based cemented carbide coatings are mainly composed of austenite, Cr23C6 and Cr7C3, and needle-like Cr23C6 precipitates are present around columnar and equiaxial dendrites of austenite. Benefited from this structural feature, the 3533-00 Fe-based cemented carbide coating has a much higher average hardness (543.4 HV0.5), which is 2.4 times harder than 304 stainless steel substrate (220 HV0.5). Moreover, the 3533–00 Fe-based cemented carbide coatings demonstrate better wear (reduction of wear volume by ∼44 %) and corrosion resistance than the Stellite 6 Co-based alloy coatings. These findings may provide a method for designing wear and corrosion resistant coatings for nuclear valve sealing surface.