The microstructures and stress-controlled fatigue behavior of austenitic stainless steel(AISI 316 L stainless steel)fabricated via laser-powder bed fusion(L-PBF)technique were investigated.For L-PBF process,zigzag las...The microstructures and stress-controlled fatigue behavior of austenitic stainless steel(AISI 316 L stainless steel)fabricated via laser-powder bed fusion(L-PBF)technique were investigated.For L-PBF process,zigzag laser scanning strategy(scan rotation between successive layer was 0°,ZZ sample)and crosshatching layer scanning strategy(scan rotation between successive layer was 67°,CH sample)were employed.By inducing different thermal history,it is found that the scan strategies of laser beam have a significant impact on grain size and morphology.Fatigue cracks generally initiated from persistent slip bands(PSBs)or grain boundaries(GBs).It is observed that PSBs could transfer the melt pool boundaries(MPBs)continuously.The MPBs have better strain compatibility compared with grain boundaries(GBs),thus MPBs would not be the initiation site of fatigue cracks.A higher fatigue limit strength could be achieved by employing a crosshatching scanning strategy.For the CH sample,fatigue cracks also initiated from GBs and PSBs.However,fatigue crack initiated from process-induced defects were observed in ZZ sample in high-cycle regions.Solidification microstructures and defects characteristics are important factors affecting the fatigue performance of L-PBF 316 L stainless.Process-induced defects originated from fluid instability can be effectively reduced by adjusting the laser scan strategy.展开更多
激光粉末床熔融(laser powder bed fusion,LPBF)增材制造技术广泛用于航空航天领域复杂结构的镍基高温合金零件的一体化制造,但是其粗糙度问题限制了该项技术的应用.基于此,通过采用双轮廓扫描策略优化表面成形质量,并研究轮廓参数的热...激光粉末床熔融(laser powder bed fusion,LPBF)增材制造技术广泛用于航空航天领域复杂结构的镍基高温合金零件的一体化制造,但是其粗糙度问题限制了该项技术的应用.基于此,通过采用双轮廓扫描策略优化表面成形质量,并研究轮廓参数的热输入对表面成形质量及微观组织、显微硬度的影响.结果表明,上表面粗糙度Sa随上轮廓参数的热输入增加逐渐降低,并在功率为220 W,扫描速度为0.1 m/s时粗糙度Sa达到3.1μm最优值,但在高热输入时近表面会形成匙孔诱发的孔洞缺陷,因此表面粗糙度优化需折衷考虑近表面孔洞缺陷;此外,双轮廓参数的热输入与下表面粗糙度之间没有明显的相关性.不同轮廓参数下制备的样品下表面粗糙度Sa在13.5~16.5μm之间;轮廓参数的单向扫描策略导致了粗大柱状晶粒的形成,并且随着热输入的增加,上层轮廓层的显微硬度显著增加。展开更多
基金the National Magnetic Confinement Fusion Science Program of China(No.2014GB117000)the Joint Funds of the National Natural Science Foundation of China(No.U1605243)。
文摘The microstructures and stress-controlled fatigue behavior of austenitic stainless steel(AISI 316 L stainless steel)fabricated via laser-powder bed fusion(L-PBF)technique were investigated.For L-PBF process,zigzag laser scanning strategy(scan rotation between successive layer was 0°,ZZ sample)and crosshatching layer scanning strategy(scan rotation between successive layer was 67°,CH sample)were employed.By inducing different thermal history,it is found that the scan strategies of laser beam have a significant impact on grain size and morphology.Fatigue cracks generally initiated from persistent slip bands(PSBs)or grain boundaries(GBs).It is observed that PSBs could transfer the melt pool boundaries(MPBs)continuously.The MPBs have better strain compatibility compared with grain boundaries(GBs),thus MPBs would not be the initiation site of fatigue cracks.A higher fatigue limit strength could be achieved by employing a crosshatching scanning strategy.For the CH sample,fatigue cracks also initiated from GBs and PSBs.However,fatigue crack initiated from process-induced defects were observed in ZZ sample in high-cycle regions.Solidification microstructures and defects characteristics are important factors affecting the fatigue performance of L-PBF 316 L stainless.Process-induced defects originated from fluid instability can be effectively reduced by adjusting the laser scan strategy.
基金National Natural Science Foundation of China(Nos.52001140,52274363)Guangdong Basic Applied Basic Research Foundation,China(Nos.2022A1515010558,2022A1515011597,2022A1515240065)。
