Sun Xin, Ren Jianbiao, Wang Yachao, Zhao Dingguo, Wang Shuhuan, Xiong Xiaojing, Rao Jeremy Heng
School of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063009, China.
Ji Hua Laboratory, Institute of Advanced Additive Manufacturing, Foshan 528200, China.
Materials (Basel). 2023 Mar 21;16(6):2505. doi: 10.3390/ma16062505.
High-nitrogen stainless steels are widely used due to their excellent comprehensive performance. In this study, the effects of process parameters (laser power, scanning speed, and cavity pressure) on the formation of high-nitrogen stainless steels were studied by using conventional selective laser melting and high-pressure selective laser melting (HPSLM). The nitrogen content, nitrogen emission, phase composition, microstructure, and microhardness of the high-nitrogen stainless steel samples obtained through selective laser melting (SLM) were analysed by using an oxygen/nitrogen/hydrogen analyser, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. The results showed that the maximum nitrogen emission in the SLM sample was 0.175 wt.%, the emission rate reached up to 54.7%, and the maximum nitrogen content in the HPSLM sample was 1.07 wt.%. There was no significant difference between the phase peak positions of the SLM samples with different laser powers and the original powder. The main phase of the HPSLM sample changed at 0.3 MPa (from α-Fe to γ-Fe phase); the microstructure of the SLM sample was mainly composed of columnar and cellular crystals, and columnar crystal bands formed along the direction of heat flow. The HPSLM sample was mainly composed of equiaxed crystals with a grain size of 10-15 μm. At an energy density of 136 J/mm, the microhardness and relative density reached their peak values of 409 HV and 98.85%, respectively.
高氮不锈钢因其优异的综合性能而被广泛应用。在本研究中，采用传统选择性激光熔化和高压选择性激光熔化（HPSLM）研究了工艺参数（激光功率、扫描速度和腔体压力）对高氮不锈钢形成的影响。通过氧/氮/氢分析仪、X射线衍射、扫描电子显微镜、能量色散X射线光谱仪和电子背散射衍射对通过选择性激光熔化（SLM）获得的高氮不锈钢样品的氮含量、氮排放、相组成、微观结构和显微硬度进行了分析。结果表明，SLM样品中的最大氮排放为0.175 wt.%，排放率高达54.7%，HPSLM样品中的最大氮含量为1.07 wt.%。不同激光功率的SLM样品与原始粉末的相峰位置之间没有显著差异。HPSLM样品在0.3 MPa时主相发生变化（从α-Fe相转变为γ-Fe相）；SLM样品的微观结构主要由柱状晶和胞状晶组成，沿热流方向形成柱状晶带。HPSLM样品主要由尺寸为10 - 15μm的等轴晶组成。在能量密度为136 J/mm时，显微硬度和相对密度分别达到峰值409 HV和98.85%。
