Li Shaoying, Xi Xiaojun, Luo Yiwa, Mao Mingtao, Shi Xiao, Guo Jing, Guo Hanjie
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing 100083, China.
Materials (Basel). 2018 Dec 7;11(12):2491. doi: 10.3390/ma11122491.
In this paper, the precipitation of carbide and wear loss of high-carbon 8 mass% Cr tool steel at two tempering conditions (i.e., 773⁻803 K and 823⁻853 K) were studied by INCA Steel, EPMA-1720H, XRD, and ML-10 tester. The results show that the particles of test steels include the carbides (Cr₇C₃ and CrC₆) and carbides nucleated on Al₂O₃. When carbides are of the same size, the number of carbides in test steel at a tempering temperature of 773⁻803 K is greater than that at a tempering temperature of 823⁻853 K, especially when the size of carbides is less than 5 μm. Compared with the test steel tempered at 823⁻853 K, the distance between adjacent actual particles reduced by 80.6 μm and the maximum amount of reduction was 9.4% for single wear loss at the tempering temperature of 773⁻803 K. It can be concluded from thermodynamics results that Al₂O₃ inclusions began to precipitate in liquid, and the precipitation of carbides was at the solid⁻liquid region. Al₂O₃ can be used as the nucleation interface of carbide, thus promoting the formation of carbides. During the cooling of molten steel, a lower temperature can increase the difference of actual solubility product bigger than equilibrium solubility product, thus promoting the carbide formation.
本文采用INCA Steel、EPMA - 1720H、XRD和ML - 10测试仪，研究了高碳8质量% Cr工具钢在两种回火条件（即773⁻803 K和823⁻853 K）下碳化物的析出及磨损损失。结果表明，试验钢中的颗粒包括碳化物（Cr₇C₃和CrC₆）以及在Al₂O₃上形核的碳化物。当碳化物尺寸相同时，回火温度为773⁻803 K的试验钢中碳化物数量多于回火温度为823⁻853 K的试验钢，尤其是当碳化物尺寸小于5μm时。与在823⁻853 K回火的试验钢相比，在773⁻803 K回火温度下，相邻实际颗粒间距减小了80.6μm，单次磨损损失最大降幅为9.4%。从热力学结果可以得出，Al₂O₃夹杂物在液相中开始析出，碳化物的析出发生在固液区域。Al₂O₃可作为碳化物的形核界面，从而促进碳化物的形成。在钢液冷却过程中，较低的温度可使实际溶解度积与平衡溶解度积的差值增大，从而促进碳化物的形成。
