固溶时效对SLM成形316L不锈钢块体件显微组织及硬度的影响

Effect of solution and aging on microstructure and hardness of 316L stainless steel block formed by SLM

采用选区激光熔化技术(Selective laser melting, SLM)成功制备了316L不锈钢块体件,借助光镜(OM)和扫描电镜(SEM)及维氏硬度计研究了不同时效工艺(时效温度分别为650℃和850℃)对SLM成形316L不锈钢块体件显微组织以及显微硬度的影响。结果表明,SLM成形316L不锈钢块体件显微组织主要由细小柱状晶和蜂窝状晶粒组成。“层-层”和“道-道”熔池边界清晰可见,经固溶时效后边界基本消失,但晶界清晰可见,再结晶晶粒呈合并生长方式长大。650℃时效时,试样中少量M_(23)C_(6)分布于晶界,显微硬度相对较高;随着时效温度的升高,850℃时效后试样的晶粒进一步长大,沿晶界形成了大量不连续M_(23)C_(6)。

316 L stainless steel block was successfully prepared by selective laser melting(SLM) technology. The effect of aging temperature(650 ℃ and 850 ℃) on microstructure and microhardness of 316 L stainless steel block formed by SLM was studied by means of optical microscope(OM), scanning electron microscope(SEM) and Vickers hardness tester. The results show that the microstructure of 316 L stainless steel block formed by SLM is mainly composed of fine columnar grains and honeycomb grains. The boundaries of “layer-layer” and “channel-channel” molten pools are clearly visible. After solution and aging, the boundaries of “layer-layer” and “channel-channel” molten pools disappear, but the grain boundaries are clearly visible and the recrystallized grain grows in a combined growth mode. A small amount of M_(23)C_(6) are distributed at grain boundaries in specimen after aging at 650 ℃, and the microhardness is relatively high. With the increase of aging temperature, the grain of specimen after aging at 850 ℃ grows further, and a large amount of discontinuous M_(23)C_(6) are formed along the grain boundaries.