Study on the process of Co-based alloy hardfacing of latch arm of control rod drive mechanism for nuclear power plant

The difficulty in Co-based alloy hardfacing of latch arm of control rod drive mechanism is eliminating the cracks and porosities of the hardfacing layer, the hardness of the hardfacing layer and the size of the latch arm not conforming to the design requirements. In order to resolve above these problems, the high quality hardfacing layer has been obtained without cracks and pores using proper heat treatment, hardfacing structure, hardfacing sequence, welding method, and thermal insulating tooling. By hardness inspection, metallographic examination and dimensional examination, the inspection results show that the hardfacing layer and the size of the latch arm meet all the design requirements. (authors)