After installation and commissioning, cracks were found in the iron-base alloy hard-faced sealing surface and the iron-base alloy hard-faced guide surface of bulk imported valve parts from a foreign valve manufacturer. After systematic analysis and testing of the typical crack-containing parts, the root cause of the weld cracks was determined and summarized. After optimizing the structure of the hard face layer and the hard-facing progress, the replacement valve parts have been proven have better crack resistance and anti-expansion ability. Above all, this provides an engineering reference for the iron-based alloy welding in nuclear power equipment applications.