Failure Analysis of M330 Plastic Mould Steel Insert

Premature failure of a plastic mould insert made of M330 steel for injecting cellphone was analyzed. The morphology and microstructure of the failed inserts working surface were analyzed by scanning electron microscopy and Rockwell hardness was also tested. The hardness of the surface micro-areas was measured by nanoindentation. It was found that the main reason resulting in the failure was the reduction of hardness and wear resistance caused by three times of tempering among which an additional tempering was aimed to the convenience of etching process. Another main factor was the change of the working surface corroded dots design, because the new design made the insert plastic flow more freely than the old one and the abrasion was aggravated.