高致密度激光选区熔化Inconel 718合金中的微小孔隙缺陷和拉伸性能

Micro-porosity and Tensile Property of High Density Inconel 718 Superalloy Fabricated by Selective Laser Melting

摘要:

本文采用激光选区熔化技术制备了高致密度Inconel 718合金试样，研究了工艺参数（激光功率，扫描速度）对合金试样致密度的影响规律，分析了孔隙缺陷的形成原因，对比研究了微小孔隙缺陷存在条件下的拉伸性能变化，并比较了热处理对不同致密度合金力学性能影响。实验结果表明：工艺参数的改变决定了激光与粉末相互作用的模式，在较高激光功率、低扫描速度条件下发生了“匙孔”模式，气孔较多，致密度降低；当功率减小或者扫描速度增大会由“匙孔”模式向“热传导”模式转变，气孔较少，致密度会升高；但是当激光功率过小或者扫描速度过大时产生未熔合孔隙缺陷，使得材料的致密度出现大幅度减小的现象。拉伸测试结果表明，激光选区熔化成形Inconel 718合金的强度并不会随着致密度的增大呈严格单调增大的变化趋势，微小孔隙缺陷的形貌、数量和尺寸也会对拉伸性能产生影响。SIDA热处理可以大幅提高激光选区熔化成形Inconel 718合金的显微硬度及抗拉强度，但塑性呈显著降低。

Abstract:

Inconel 718 alloy samples with different densities were prepared by selective laser melting technology. The influence of processing parameters including laser power and scanning speed on the density of alloy samples was studied. The formation causes of micro pore defects and its effect on the tensile property were analyzed. The mechanical properties of alloys with different densities were studied by SIDA heat treatmet. The results showed that the interaction mode between laser and powder was determined by processing parameters. The "keyhole" mode occurred under the condition of high laser power and low scanning speed, which resulted in the decrease of density. When the power decreased or the scanning speed increased, the "keyhole" mode would change to the "heat conduction" mode, and the density would increase. However, when the laser power was too small or the scanning speed was too large, the unfused pore defects would occur, which would greatly reduce the density of the sample. The strength of the selective laser melting Inconel 718 alloy sample did not increase in a strictly monotonic manner with increasing the density. The morphology, quantity and size of the micro pore defects also had an effect on the tensile properties of the samples. SIDA heat treatment can greatly improve the microhardness and tensile strength of selective laser melting formed Inconel 718 alloy, but the plasticity is significantly reduced.