Effects of nanoparticle addition on hardening and tempering steel

The effects of nanoparticle addition on the hardening and tempering 20MnCr steel have been investigated. Addition of oxide nanoparticles to the melt, through a new technology that ensures safe handling, was found to give as hardened steel hardness and tensile properties close to those of the conventional steel in the hardened and tempered condition. This has the potential to eliminate the tempering step in component production, with benefits for process efficiency. The effects on microstructure, hardness and tensile properties depend on the type and concentration of the nanoparticles added. The reduced tensile strength and hardness, and increased ductility, of the steels with nanoparticle additions are attributed to the presence of retained ferrite in these microstructures, in both the hardened and tempered condition. It is proposed that the application of this approach at an industrial scale has the potential to reduce energy consumption, cost and time in component production through the elimination of intermediate operations such as tempering.