Laser powder bed fusion (L-PBF) of Co–28Cr–6Mo alloy is a powerful tool for many engineering applications but one has to be familiar with its microstructural instability in the as-produced state. In our previous study [Roudnicka et al., Additive Manuf. 44 (2021) 102025], we depicted the phenomenon of this instability when exposing the material to temperatures above 673 K. Microstructural changes bringing about hardening of the material were studied thoroughly. In the present study, we follow up by revealing the effect of this hardening on mechanical properties in tension and show the beneficial effect of heat treatment on removing the observed instability. Hardening associated with increasing the proportion of HCP ε-phase and with the precipitation of σ-phase has a detrimental effect on material plasticity and can be negatively affect the fatigue too. We thus applied a two-stage heat treatment comprising solution annealing at 1473 K/2 h and aging at 1173 K/5 h. Not only it induced material stability but also increased the material strength with not such a detrimental decrease in material plasticity as was brought by direct aging at 1173 K/5 h.

激光粉末床融合（LCo-28Cr-6Mo 合金的 -PBF) 是许多工程应用的强大工具，但必须熟悉其在生产状态下的微观结构不稳定性。在我们之前的研究中 [Roudnicka et al., Additive Manuf. 44 (2021) 102025]，我们描述了将材料暴露于 673 K 以上的温度时的这种不稳定性现象。彻底研究了导致材料硬化的微观结构变化。在本研究中，我们进一步揭示了这种硬化对拉伸机械性能的影响，并展示了热处理对消除观察到的不稳定性的有益影响。与 HCP ε 相比例增加和 σ 相析出相关的硬化对材料塑性有不利影响，也会对疲劳产生负面影响。因此，我们采用了两阶段热处理，包括在 1473 K/2 h 下固溶退火和在 1173 K/5 h 下时效。它不仅提高了材料稳定性，而且还提高了材料强度，而不会像在 1173 K/5 小时下直接老化所带来的材料塑性降低那样有害。