Effects of plasma surface quenching on strength and crack resistance property of PCrNi3 Mo steel

Abstract

Plasma surface quenching technology uses a high-energy beam to rapidly heat the PCrNi3Mo steel material. Simultaneously, the treated workpiece is rapidly cooled by its own heat transfer to realize surface quenching. The metallographic structure showed that the grains of the PCrNi3Mo steel treated by plasma quenching were significantly refined. The DEFORM software was utilized to simulate the heat treatment process, and the results showed that the martensitic volume fraction of the plasma quenching treatment of PCrNi3Mo steel was as high as 83.6%~95.9%, and the simulated hardness value was HRC55~57. The actual hardness of the specimen after plasma surface quenching was HRC54~56, which was in good agreement with the simulation value. The plasma was employed to treat the PCrNi3Mo steel tensile specimen, the processing depth was only 1/10 of the thickness of the specimen. Through the MTS tensile experiment, it was observed that the tensile strength of specimens treated with plasma increased by 9.2% when compared to the untreated specimens. Despite the high hardness of the treated specimen, fracture strain exceeded 7%. Furthermore, before the fracture of the tensile specimen occurred, the plasma quenching part effectively prevented crack propagation and delayed fracture, and the fracture necking phenomenon of the specimen was not obvious.