合金成分对GH4099合金激光选区熔化成形组织及性能的影响

Effect of alloy composition on the microstructure and properties of GH4099 alloy formed by Selective Laser Melting

通过激光选区熔化成形工艺制备不同成分的GH4099合金试样,研究不同合金成分对组织形貌及其力学性能的影响规律。结果表明,三组成分GH4099合金打印成形态组织均无明显的缺陷,但经固溶热处理后晶粒等轴化程度有所差异,主要是由于C、Cr、Mo、W、Ti等碳化物形成元素差异促使GH4099合金中碳化物特征差异所致。各成分GH4099合金900℃拉伸强度和塑性具有明显的差异,与各合金等轴化程度及其组织中碳化物的分布位置和形态有明显关联,等轴状晶粒晶界非连续分布的碳化物与晶内弥散分布的细小颗粒状M23C6型碳化物有利于保持较高的强度和塑性;初始组织中较高含量的MC型碳化物沿晶界连续分布,钉扎晶界导致晶粒等轴化程度较低,展现强度高、塑性低的特点,断口形貌呈现沿原始柱状晶晶界断裂。Ti元素等促MC型碳化物形成元素对晶粒等轴化不利,同时沿晶界连续分布的MC型碳化物不利于900℃拉伸塑性,Cr、Mo、W等促M_(23)C_6型碳化物形成元素,虽对晶粒等轴化有所影响,但可通过固溶强化提高高温强度,在900℃保持较好的塑性。

The GH4099 alloy samples with different compositions were printed using selective laser melting manufacture, the influence of different alloy compositions on the microstructure and mechanical properties was investigated. The results showed that there were no obvious defects in the as-printed microstructure of the three component GH4099 alloy, but there were differences in the degree of equiaxation of the columnar grains after solution heat treatment, mainly due to differences in the carbides formation elements such as C, Cr, Mo, W, and Ti, which led to different characteristics of carbides in GH4099 alloy. The tensile strength and plasticity of GH4099 alloy at 900 ℃ have significant differences among different compositions, which are significantly related to the degree of equiaxation and the distribution position and morphology of carbides in the microstructure of each alloy. The discontinuous distribution of carbides at equiaxed grain boundaries and the dispersed distribution of fine M_(23)C_6 type carbides within grains are beneficial for maintaining high strength and plasticity. The high content of MC type carbides in the initial microstructure is continuously distributed along the grain boundaries,and pinning the grain boundaries results in a lower degree of equiaxation of the columnar grains, exhibiting high strength and low plasticity. The fracture morphology shows fracture along the original columnar grain boundaries. Ti and other elements that promote the formation of MC type carbides are not beneficial to grain equiaxation and detrimental to tensile plasticity at 900 ℃ attributed for the continuously distributed MC type carbides along grain boundaries. Cr, Mo, W and other elements that promote the formation of M_(23)C_6 type carbides have an impact on grain equiaxation, but can improve high-temperature strength through solid solution strengthening and maintain good plasticity at 900 ℃.