Vutova Katia, Stefanova Vladislava, Markov Martin, Vassileva Vania
Institute of Electronics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.
Department of Metallurgy of Non-Ferrous Metals and Semiconductors Technologies, University of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria.
Materials (Basel). 2023 Mar 26;16(7):2634. doi: 10.3390/ma16072634.
The hardness of heat (thermally) treated CoCrMo ingots, recycled by electron beam melting and refining (EBMR) of a technogenic CoCrMo material (waste from the dental technology) under different process conditions (temperature and residence time) is examined. The heat treatment consists of two-step heating up to temperatures of 423 K and 1343 K and retention times of 40 and 60 min, respectively. The influence of various loads (0.98 N, 1.96 N, 2.94 N, 4.9 N, and 9.8 N) on the hardness of the CoCrMo alloy, recycled by EBMR, before and after heat treatment is studied. It has been found that regardless of the EBMR process conditions, the obtained samples after heat treatment have similar hardness values (between 494.2 HV and 505.9 HV) and they are significantly lower than the hardness of the specimens before the heat treatment. The highest hardness (600 HV) is measured in the alloy recycled at 1845 K refining temperature for 20 min. This is due to the smaller crystal structure of the resulting alloy and the higher cobalt content. The results obtained show that the heat treatment leads to considerable changes in the microstructure of the CoCrMo ingots recycled by EBMR. With the increase of the e-beam refining temperature, after the heat treatment, the grains' size increases and the grains' shape indicates an incomplete phase transition from γ-fcc to ε-hcp phase. This leads to a slight increase in the hardness of the alloy.
研究了通过电子束熔炼和精炼（EBMR）对一种技术钴铬钼材料（牙科技术废料）在不同工艺条件（温度和停留时间）下进行回收得到的热处理钴铬钼铸锭的硬度。热处理包括两步加热，分别加热到423K和1343K，保温时间分别为40分钟和60分钟。研究了不同载荷（0.98N、1.96N、2.94N、4.9N和9.8N）对经EBMR回收的钴铬钼合金在热处理前后硬度的影响。结果发现，无论EBMR工艺条件如何，热处理后得到的样品具有相似的硬度值（在494.2HV和505.9HV之间），且显著低于热处理前试样的硬度。在1845K精炼温度下回收20分钟的合金中测得最高硬度（600HV）。这是由于所得合金的晶体结构较小且钴含量较高。所得结果表明，热处理导致经EBMR回收的钴铬钼铸锭的微观结构发生显著变化。随着电子束精炼温度的升高，热处理后，晶粒尺寸增大，晶粒形状表明从γ-fcc到ε-hcp相的相变不完全。这导致合金硬度略有增加。
