This paper aims to the new process of QPQ salt bath composit processing technology that applied to the components of retarder brief introduce its processing character and it also anlyzes the condition of applying of the technoeogy in the cylinder and piston rod of retarder.

Effect of QPQ complex salt bath heat treatment on wear resistance of ductile cast iron has been studied,which has been pretreated to get different ferrite content with 900℃ normalizing and temper at different heat.

The film obtained by Quench-Polish-Quench technology had high corrosion resistance at room temperature and that by chemical Ni-P plating had the best oxidation resistance at 480℃and 570℃.

QPQ technology is a new surface modification and strengthening technology for metals.