Effects of Vacuum-Carburizing Conditions on Surface-Hardened Layer Properties of Transformation-Induced Plasticity-Aided Martensitic Steel

• Main Authors: Koh-ichi Sugimoto, Tomohiko Hojo, Yuta Mizuno
• Format: Article
• Language: English
• Published: MDPI AG 2017-08-01
• Series: Metals
• Subjects: vacuum-carburization; carbon potential; fine-particle peening; TRIP-aided martensitic steel; retained austenite; microstructure; hardness; residual stress
• Online Access: https://www.mdpi.com/2075-4701/7/8/301
• ISSN: 2075-4701

The effects of carbon potential in vacuum-carburization on the surface-hardened layer properties of the 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb transformation-induced plasticity-aided martensitic steel were investigated for the fabrication of precision gears. The volume fraction of retained austenite and hardness in the surface hardened layer of the steel increased with increasing carbon potential. Subsequent fine-particle peening enhanced the hardness and the compressive residual stress via severe plastic deformation and strain-induced martensite transformation, especially under a high carbon potential. The severe plastic deformation mainly contributed to increased hardness and compressive residual stress and the contribution of the strain-induced martensitic transformation was relatively small.