Microstructure features of 24CrNiMo alloy steel fabricated by laser additive manufacturing

Abstract

Herein, the single-track and block samples of 24CrNiMo alloy steel were prepared by selective laser melting (SLM) technology and laser melting deposition (LMD) technology. The phase composition, microstructure, texture types and micro-hardness of 24CrNiMo low alloy steel under two laser irradiation conditions were studied. The results show that the main phase compositions of 24CrNiMo alloy samples prepared by two methods are α-Fe phase and a small amount of Fe3C.Furthermore, the grain orientation of SLM single-track deposited sample is random and disordered, and there is no obvious preferred orientation.However, the preferred orientation of LMD single-track deposited sample is the (110)〈101〉 plane texture. The grain of SLM block sample has weak 〈111〉 texture parallel to the deposition direction, LMD block sample has strong texture with the 〈111〉epitaxial growth orientation.Additionally, the main microstructure of as-built SLM sample is lower bainite, and the microstructure of as-deposited LMD sample mainly consists of lathbainite. The average micro-hardness SLM sample with fine grain and lower bainite microstructure is higher than that of LMD sample.

Keywords

• selective laser melting
• laser melting deposition
• 24crnimo alloy steel
• microstructure
• texture