Carbon partitioning and structure evolution in the hardening treatments of high strength steel
In this paper, we report the microstructural evolution and carbon partitioning behaviour of an alloyed medium carbon steel in continuous quenching and the subsequent tempering process. The obtained samples were characterized by XRD with Gaussian peak-fitting analysis, field-emission-gun SEM, and TEM. It has been found that, the oil quenched sample was hardened to HV 742, exhibiting a mixed microstructure of plate- and lath-type martensites with a 8.0％ volume fraction of retained austenite, as well as a small number of un-dissolved carbide particles. Carbon partitioning was evidenced in the as-quenched structure by supersaturation of carbon to 0.93 wt％ in the retained austenite. Moreover, careful peak-fitting analysis of the martensite diffraction peak 200M suggested the existence of two martensitic structures having different carbon contents, namely 0.41％ and 0.19 wt％ respectively, which corresponded to the lath- and plate-type martensites as verified by TEM observation. Slower cooling rates in thick samples have been found to facilitate more pronounced carbon partitioning, which included the diffusion of carbon from the newly formed martensite to the un-transformed austenite and the precipitation of carbide particles in the martensite/ferrite matrix. Subsequent tempering following the quenching treatment resulted in a decrease in hardness from 677HV to 542HV due to the recovery of lattice strains in the martensite and, when tempered at 300℃ or higher temperatures, significant decrease in carbon contents with martensite.
carbon partitioning heat treatments steel X-ray diffraction gaussian peak-fitting
Quanshun Luo Matthew Kitchen Vinay Patel Stephen Magowan
Materials and Engineering Research Institute, Sheffield Hal lam University,Howard Street, Sheffield, S11WB, UK
国际会议
北京
英文
111-117
2012-10-23（万方平台首次上网日期，不代表论文的发表时间）