Achieving high fracture toughness and tribological properties in high-carbon steels via sub-zero treatment and low-temperature tempering

摘要

High-carbon martensitic steel possesses extraordinary strength and hardness but inferior fracture toughness, restraining its utilization under high-performance conditions. In the present study, a significant improvement in fracture toughness and tribological properties of high-carbon steel were achieved via a conjugation of sub-zero treatment (SZT) at 233 K for 24 h and low-temperature tempering at 473 K for 2 h owing to the formation of nanoscale transition eta-carbides in a well-distributed manner. Subsequently, the scratch test followed by quantitative analysis of fracture toughness (K(I)c) was carried out on the tiny samples in order to minimize the heterogeneous effects after treatments. SZT sample revealed high value of K(I)c of similar to 43 MPa root m which was higher than conventional counterpart of similar to 29 MPa root m. Additionally, SZT sample showed outstanding nanohardness value of similar to 8 GPa than that of CT of similar to 6 GPa. The underlying mechanisms will be elaborated based on the microstructural analysis and fracture behavior. (C) 2019 Elsevier B.V. All rights reserved.