Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting
Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting
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热处理冷却条件对选区激光熔炼钴铬钼合金组织和疲劳性能的影响
DOI：
10.3390/met11071005
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发表时间：
2021-06
期刊：
影响因子：
2.9
通讯作者：
Hla Htoot Wai Cho;Atsushi Takaichi;Yuka Kajima;Hein Linn Htat;Nuttaphon Kittikundecha;T. Hanawa;N. Waka
中科院分区：
文献类型：
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作者：
Hla Htoot Wai Cho;Atsushi Takaichi;Yuka Kajima;Hein Linn Htat;Nuttaphon Kittikundecha;T. Hanawa;N. Waka
虽然后热处理可以提高选择性激光熔化（SLM）制造的钴铬钼（CoCrMo）合金的疲劳寿命，冷却条件对这种合金的疲劳性能的影响仍然不清楚。在这项研究中，我们制作了SLM CoCrMo合金试样，并在热处理后，通过水冷（FC）或空冷（AC）冷却。随后，我们使用扫描电子显微镜结合能量色散X射线光谱，电子背散射衍射，共聚焦激光扫描显微镜和X射线衍射分析了它们的微观结构。拉伸和维氏硬度（HV）测试和轴向疲劳测试也进行了评估其机械和疲劳性能，分别。所有试样的显微组织均为均匀的等轴晶，AC试样的晶粒尺寸（84.9 μm）小于FC试样的晶粒尺寸（109.7 μm）。AC样品表现出比FC样品更好的延展性。然而，我们在0.2%屈服强度和HV试验中未观察到显著差异。疲劳试验的S-N曲线表明AC试样的疲劳寿命大于FC试样。因此，在后热处理期间的高冷却速率在减小晶粒和沉淀物尺寸方面是有效的，从而导致改善的延展性和疲劳寿命。
Although post-heat treatment can improve the fatigue life of selective laser melting (SLM)-fabricated cobalt chromium molybdenum (CoCrMo) alloys, the effect of cooling conditions on the fatigue properties of such alloys remains unclear. In this study, we fabricated SLM CoCrMo alloy specimens and, after heat-treating them, cooled them either via furnace-cooling (FC) or air-cooling (AC). Subsequently, we analyzed their microstructures using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, electron backscattered diffraction, confocal laser scanning microscopy, and X-ray diffraction. Tensile and Vickers hardness (HV) tests and axial-fatigue tests were also conducted to assess their mechanical and fatigue properties, respectively. The microstructures of all samples showed homogeneous equiaxed grains, with the grains and precipitates of the AC samples (grain size: 84.9 μm) smaller than those of the FC samples (grain size: 109.7 μm). The AC samples exhibited better ductility than the FC samples. However, we observed no significant differences in the 0.2% yield strength and HV tests. The S–N curve derived from the fatigue tests showed that the AC samples had greater fatigue life than the FC samples. Therefore, a high cooling rate during post-heat treatment is effective in reducing grain and precipitate sizes, resulting in improved ductility and fatigue life.