The Impact of Prenitriding on the Microstructure and Mechanical Properties of the Carburized Surface Layer in a Martensitic Stainless Steel

Herein, it is proposed to obtain a favorable combination of microstructure and mechanical properties of martensitic stainless steel 14Cr14Co13Mo5 by prenitriding method before carburizing and appropriate heat treatment processes. The result indicates that the effective hardened layer depth is increased by 32% to 0.66 mm, and the hardness is significantly improved by prenitriding. The confocal laser scanning microscope and electron backscattered diffraction show that the prenitriding can effectively refine the martensite substructure of the carburized layer after quenching due to the refinement of prior austenite grain. In addition, plenty of second-phase particles M2N with finer size appear at the same case layer depth instead of coarse M23C6 in the specimen prenitrided, which optimize the microstructure of the case layer.