对中碳Fe-0.4 C-1.5 Mn-1.5 Si钢,以传统的淬火-回火试样作对比,研究了三种奥氏体化温度处理后淬火-配分试样的干滑动摩擦磨损性能。结果发现,860 ?C和1000 ?C全奥氏体化处理的两种淬火-配分试样中残余奥氏体的含量相近(分别为~14.37 vol.%和~13.79 vol.%),其内的碳浓度较高(分别为1.37 wt.%和1.38 wt.%),机械稳定性较强。在恒定低载荷(50 N)和恒定低滑动速度条件(40 mm/s)下,摩擦过程中不易诱发马氏体相变,导致两种试样的耐摩擦摩损性能均很低。受显微组织细化影响,奥氏体化温度较低的试样具有更高的耐摩性。当奥氏体化温度降低到800 ?C时,获得临界淬火-配分的试样。显微组织分析表明,该试样中不仅包含少量的铁素体(~6.75 vol.%),而且存在最高含量的残余奥氏体(~22.28 vol.%),使得在四组试样内的显微硬度值最低。但由于低的碳浓度(~1.06 wt.%),残余奥氏体的机械稳定性较弱,在摩擦过程中易诱发马氏体相变,不仅贡献额外的硬化,而且马氏体相变体积膨胀引起的材料表面层压应力对提高耐磨性也有利,由此导致临界淬火-配分试样表现出最好的耐磨损性能。因此,在给定的摩擦参数条件下,残余奥氏体对马氏体钢抗磨损性能的影响主要决定于在摩擦过程中是否能经相变而引起附加的硬化作用。
Effect of retained austenite on the wear property of martensitic steel is still in controversial by now. Selecting traditional quenching and tempering (Q&T) sample with identical composition Fe-0.4C-1.5Mn-1.5Si as reference, the dry sliding wear property of quenching and partitioning (Q&P) samples with different austenitization temperatures was studied. The results show that the volume faction of retained austenite in the Q&P samples with full austenitization at 860 ?C or 1000 ?C respectively is nearly same (~14.37 vol.% in the former and ~13.79 vol.% in the later). The corresponding carbon concentration in retained austenite is relatively high (1.37 wt.% in the former and 1.38 wt.% in the later). Therefore, its mechanical stability is very strong. Under the conditions of constant low loading (50 N) and slide speed (40 mm/s), it is not easy to induce martensitic transformation. Which results in the low friction and wear resistance of these two kinds of samples. The slight better in wear resistance of samples with low austenitization temperature can be attributed to the microstructural refinement. When the austenitization temperature was reduced to 800 ?C, the critical Q&P samples were obtained. Microstructure analysis indicates there exist the highest volume fraction of retained austenite (~22.28 vol.%) plus a small amount of ferrite (~6.75 vol.%) in martensitic matrix, which results in the lowest microhardness among present four kinds of samples. However, the mechanical stability of these retained austenites is weak due to low carbon concentration (~1.06 wt.%). The obvious martensitic transformation occurred accompanying sliding wear, contributing to extra hardening and providing additional compressive stress on the touching surface caused by volume expansion. Therefore, the critical Q&P samples with austenitization temperature at 800 ?C exhibit the best wear resistance among present four kinds of samples. Based on experimental results, it is true that it is the weak mechanical stability, but not the amount only, of retained austenite in martensitic steel, plays critical role in improving wear resistance by additional hardening from martensitic transformation.