Influence of laminar plasma surface quenching on the microstructure and corrosion resistance of AISI 52100 bearing steel

In this work, the effect of laminar plasma quenching on microstructure and corrosion resistance of AISI 52100 bearing steel was studied and its mechanism was discussed. The results indicate that the microstructure of bearing steel material treated by laminar plasma quenching changed from tempered martensite to fine cryptocrystalline martensite, and the quantity of carbide obviously decreased. The average grain size is 746 nm, the carbide content is 3.5 %, and the microhardness is 900 HV0.5. The self-corrosion current density of the treated material is 1.8456 x 10-5 A/cm2 in 3.5 wt% NaCl solution, and it has excellent corrosion resistance. The carbon atoms more easily dissolved into alpha-Fe to form a supersaturated solid solution due to rapid high-temperature heating and cooling during laminar plasma treatment. The decrease in the amount of carbides after laminar plasma quenching is the cause for the improvement in the corrosion resistance of the bearing steel.