In the current investigation, a comparison between two type 4130 low-alloy steel powders produced by both gas and water atomization, and later processed by Laser-powder bed fusion was carried out. Samples fabricated from the water atomized powder showed relative density levels exceeding 99%, slightly lower than those achieved with the gas atomized powder. Both steels exhibited similar metallurgical features after solidification, showing a microstructure that is mainly composed of partially tempered martensite, bainite, and retained austenite. Additionally, micro-segregation of alloying elements was detected in the as-built microstructure, which contribute to a local increase in microhardness. The excess of oxygen found in the water atomized powder tended to combine with silicon and form nano-sized SiO₂ inclusions. During the laser processing, the complex heating and cooling effects generated by adjacent laser tracks and by overlapping layers led to an in-situ tempering of the fresh martensite. Accordingly, the hardness values of steels in as-built condition were equivalent to those of conventionally quenched samples tempered at 350 °C and 450 °C, for gas atomized and water atomized steels, respectively. Finally, a comparison in terms of mechanical properties of the investigated steels showed that the powder atomization process resulted in limited changes in steel performance.

在本次调查中，对气雾化和水雾化两种4130型低合金钢粉末进行比较，然后进行激光粉末床熔合处理。由水雾化粉末制成的样品显示出超过 99% 的相对密度水平，略低于气体雾化粉末所达到的密度。两种钢在凝固后表现出相似的冶金特征，显示出主要由部分回火马氏体、贝氏体和残余奥氏体组成的显微组织。此外，在竣工微观结构中检测到合金元素的微观偏析，这有助于显微硬度的局部增加。在水雾化粉末中发现的过量氧倾向于与硅结合并形成纳米尺寸的 SiO ₂夹杂物。在激光加工过程中，相邻激光轨迹和重叠层产生的复杂加热和冷却效应导致新鲜马氏体的原位回火。因此，对于气体雾化钢和水雾化钢，在建造状态下钢的硬度值与在 350 °C 和 450 °C 下回火的常规淬火样品的硬度值相当。最后，对所研究钢的机械性能的比较表明，粉末雾化过程导致钢性能的变化有限。