Prochaska Stephanie, Raikar Subbarao, Hildreth Owen
Department of Mechanical Engineering, Materials Science Program, Colorado School of Mines, Golden, Colorado, USA.
Department of Mechanical Engineering, Colorado School of Mines, Golden, Colorado, USA.
3D Print Addit Manuf. 2024 Aug 20;11(4):1523-1532. doi: 10.1089/3dp.2022.0346. eCollection 2024 Aug.
The poor surface finish of as-printed (AP) laser powder bed fusion (L-PBF) 316L stainless steels has detrimental impacts on the resulting fatigue and corrosion performance. One postprocessing method, a self-terminating etching process (STEP), can improve the surface finish of parts up to 76%, but the resulting effects on fatigue life and corrosion reliability remain unknown. This work evaluates the effect of the STEP on the fatigue and corrosion performance of L-PBF 316L. In addition, to determine the influence of changing the microstructures from the as-built condition, specimens having undergone a pre-STEP stress relief (SR + STEP) heat treatment and a pre-STEP solution anneal (SA + STEP) were evaluated. The results showed that a pre-STEP SR resulted in the best Sa roughness, while a pre-STEP SA had the biggest improvement in Sv roughness. Despite Sv roughness being a major indicator of fatigue performance, the coarse grains and internal porosity in the SA specimens resulted in the poorest fatigue performance. The SR + STEP specimens' fatigue lives were 10 × higher than the AP samples under a load of 275 MPa and 2-3 × higher under a 350 MPa load. The SR + STEP specimen also had the best corrosion performance in a sodium chloride electrolyte due to the smoother surface and least remnant surface carbides.
增材制造（AP）的激光粉末床熔融（L-PBF）316L不锈钢的表面光洁度较差，会对其疲劳和耐腐蚀性能产生不利影响。一种后处理方法，即自终止蚀刻工艺（STEP），可将零件的表面光洁度提高76%，但该工艺对疲劳寿命和耐腐蚀可靠性的影响尚不清楚。本文评估了STEP对L-PBF 316L疲劳和耐腐蚀性能的影响。此外，为了确定改变增材制造状态下微观结构的影响，还评估了经过STEP前应力消除（SR + STEP）热处理和STEP前固溶退火（SA + STEP）的试样。结果表明，STEP前进行SR处理可获得最佳的Sa粗糙度，而STEP前进行SA处理则在Sv粗糙度方面有最大的改善。尽管Sv粗糙度是疲劳性能的主要指标，但SA试样中的粗大晶粒和内部孔隙导致其疲劳性能最差。在275MPa的载荷下，SR + STEP试样的疲劳寿命比AP试样高10倍，在350MPa的载荷下高2至3倍。由于表面更光滑且残余表面碳化物最少，SR + STEP试样在氯化钠电解液中也具有最佳的耐腐蚀性能。
