Effects of Dual‐Phase Region Quenching Treatment on Microstructure and Mechanical Properties of 24CrNiMo Low‐Alloy Steel Prepared by Selective Laser Melting

Abstract

Herein, 24CrNiMo low‐alloy steel is successfully prepared using selective laser melting (SLM) technology. Effects of dual‐phase region quenching treatment on microstructure and mechanical properties of SLM 24CrNiMo low‐alloy steel are analyzed. The results show that after three kinds of dual‐phase region quenching treatment, different martensite–ferrite dual‐phase microstructure of the as‐quenched alloy steel is obtained. In the range of austenitizing temperature from 760 to 820 °C, the content and size of the ferrite decrease; on the contrary, the content and size of the martensite increase. Furthermore, with the austenitizing temperature increasing, the morphology of the ferrite gradually changes from acicular ferrite + polygonal ferrite to acicular ferrite, while the lath characteristics of the martensite become more and more obvious. For electron backscatter diffraction results, with increasing the quenching temperature, the crystallographic morphology gradually changes from columnar grains to equiaxed grains; meanwhile, the extreme value of texture strength and the average size of grains are both decreased. When the austenitizing temperature is 820 °C, the microhardness and tensile strength of the as‐quenched alloy steel are much higher than that of the as‐deposited alloy steel.