Laser metal deposition (LMD) as an additive manufacturing (AM) is widely used to repair and extend wear and fatigue life of the critical components. This paper has investigated the application of ball burnishing (BB) to improve surface integrity and high-cycle fatigue resistance of LMDed AISI 431 alloys. Results showed that the BB treated samples exhibited significant surface finish improvement by lowering roughness by 91 %. Microhardness increased from 490 to 530 HV0.1, an increase by 10 % with a modified depth of 400 µm from the top surface. XRD results showed a peak shift and increase in FWHM by up to 17 %. This had been corroborated by EBSD exhibiting a 20 % increase in dislocation density and 24 % increase in localised misorientation within microstructure. As a result, the overall high cycle fatigue strength of the burnished sample increased by 50 %, and the cracks initiated from sub-surface level defects at a depth of 350 μm below the top surface, delaying the crack propagation and fracture failure. The findings clearly highlight that the burnishing treatment can be a plausible approach in improving the dynamic fatigue resistance and the overall service life of LMDed AISI 431 steel alloys components in engineering applications.

中文翻译：

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塑性球抛光改性直接激光金属沉积 AISI 431 合金的表面完整性和高周疲劳寿命


激光金属沉积（LMD）作为增材制造（AM）的一种，广泛用于修复和延长关键部件的磨损和疲劳寿命。本文研究了球磨光 (BB) 的应用，以提高 LMDed AISI 431 合金的表面完整性和高周疲劳抗力。结果表明，经过 BB 处理的样品表面光洁度显着提高，粗糙度降低了 91%。显微硬度从 490 HV0.1 增加到 530 HV0.1，距离顶面的深度修改为 400 µm，增加了 10%。 XRD 结果显示峰值发生偏移，并且半峰宽 (FWHM) 增加了高达 17%。 EBSD 证实了这一点，显示位错密度增加了 20%，微观结构内的局部取向差增加了 24%。结果，抛光样品的整体高周疲劳强度提高了50%，并且裂纹从顶面以下350μm深度的亚表面级缺陷开始，延缓了裂纹扩展和断裂失效。研究结果清楚地表明，抛光处理可能是提高 LMDed AISI 431 钢合金部件在工程应用中的动态疲劳抗力和整体使用寿命的可行方法。