Liquid Metal Embrittlement of Flange Connector Studs in Contact With Cadmium

Four cadmium-plated ASTM A193 grade B studs from a steam line connector associated with a power turbine failed unexpectedly in a nil-ductility manner. Fracture surfaces were covered with a light-colored, lustrous deposit. Optical microscope, SEM, and EDS analyses were conducted on sections from one of the studs and revealed that the coating on the fracture surface was cadmium. The fracture had multiple origins, and secondary cracks also contained cadmium. The fracture topography was intergranular. The failures were attributed to liquid metal embrittlement caused by the presence of a cadmium plating and operating temperatures at approximately the melting point of cadmium. It was recommended that components exposed to the cadmium be replaced.