Zhang Yun, Lai Richen, Chen Qiang, Liu Zhen, Li Ruiqing, Chen Jufei, Chen Pinghu
State Key Laboratory of High Performance Complex Manufacturing, Light Alloys Research Institute, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
College of Mechatronics & Control Engineering, Shenzhen University, Shenzhen 518060, China.
Materials (Basel). 2021 Aug 3;14(15):4343. doi: 10.3390/ma14154343.
In this study, four kinds of heat treatments were performed to obtain a certain amount of retained austenite, which can result in good toughness and low brittleness accompanied with wear resistance of an in situ VC particle reinforced iron-based composite (VCFC). Microstructure, mechanical properties and wear resistance of the samples under heat treatment of QP, QPT, MQP and MQPT were compared. The experimental results indicated that there is a huge difference in microstructure between MQPT and the other heat treatments. High-proportion retained austenite and white net-like precipitates of MC carbide existed in the MQPT-treated sample, but thick MC carbide with brittleness was discovered in the other sample. Thereby, high-proportion retained austenite contributed to its low hardness of 634 HV and high tensile strength of 267 MPa, while a maximum hardness of 705.5 HV and a minimum tensile strength of 205 MPa were exhibited in the QPT-treated sample with a V-rich carbide of high hardness, a Cr-rich carbide of brittleness and a high-proportion martensite. Meanwhile, a phase transformation from retained austenite to martensite could increase the hardness and enhance wear resistance based on the transformation-induced plasticity (TRIP) effect; its wear rate was only 1.83 × 10 mm/(N·m). However, the wear rates of the samples under QP, QPT and MQP heat treatments increased by 16.4%, 44.3% and 41.0%, respectively. The wear mechanism was a synergistic effect of the adhesive wear mechanism and the abrasive wear mechanism. The adhesive wear mechanism was mainly considered in the MQPT-treated sample to reduce the wear rate attributed to high-proportion retained austenite and the existence of wear debris with a W element on the surface of the wear track. However, the abrasive wear mechanism could exist in the other samples because of a lot of thick, brittle MC, thereby resulting in a higher wear rate due to immediate contact between the designed material and the counterpart.
在本研究中，进行了四种热处理以获得一定量的残余奥氏体，这可使原位VC颗粒增强铁基复合材料（VCFC）具有良好的韧性和低脆性，并兼具耐磨性。比较了经QP、QPT、MQP和MQPT热处理的样品的微观结构、力学性能和耐磨性。实验结果表明，MQPT与其他热处理的微观结构存在巨大差异。经MQPT处理的样品中存在高比例的残余奥氏体和MC碳化物的白色网状析出物，但在其他样品中发现了具有脆性的粗大MC碳化物。因此，高比例的残余奥氏体导致其硬度低至634 HV，抗拉强度高至267 MPa，而经QPT处理的样品中，由于存在高硬度的富V碳化物、脆性的富Cr碳化物和高比例的马氏体，表现出最大硬度705.5 HV和最小抗拉强度205 MPa。同时，基于相变诱发塑性（TRIP）效应，残余奥氏体向马氏体的相变可提高硬度并增强耐磨性；其磨损率仅为1.83×10⁻⁶ mm²/(N·m)。然而，经QP、QPT和MQP热处理的样品的磨损率分别增加了16.4%、44.3%和41.0%。磨损机制是粘着磨损机制和磨料磨损机制的协同作用。在经MQPT处理的样品中，主要考虑粘着磨损机制以降低磨损率，这归因于高比例的残余奥氏体以及磨损轨迹表面上存在含W元素的磨损碎屑。然而，由于存在大量粗大、脆性的MC，其他样品中可能存在磨料磨损机制，从而由于设计材料与配对物之间的直接接触而导致更高的磨损率。
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