HVOF Coating Case Study for Power Plant Process Control Ball Valve Application

This case study is the result of an investigation on HVOF Cr₃C₂-NiCr coating failure of on-off metal seated ball valve (MSBV) used in supercritical steam lines in a power plant and solution. HVOF Cr₃C₂-NiCr coating is used to protect thousands of MSBVs without incident. However, in this case the valves are challenged with exposure to rapid high pressure and temperature variation resulting in a unique situation where the coating experiences cracking and cohesive failure. A detailed investigation was undertaken by Velan, Kennametal Stellite, the National Research Council of Canada and the Ecole Polytechnique to determine possible failure cause and develop solutions in which highlights are presented.