【作者】 韩同同；

【导师】 索进平；

【作者基本信息】 华中科技大学 ， 材料工程， 2011， 硕士

【摘要】 高铬白口铸铁因其优良的耐磨料磨损性能被广泛应用在抗磨料磨损的铸造设备上。国外进口的高铬白口铸铁钢管,具有好的耐磨料磨损性能,为了揭示其优良耐磨性的原因,对其组织进行了研究。金相和XRD研究发现其基体为马氏体,并含有大量弥散不连续分布高硬度合金碳化物。通过销-盘磨损实验,与正火态的45#钢对比,发现其相对耐磨性约为45#钢的2.5倍。并通过对磨损面形貌、磨屑形貌分析表明,高铬白口铸铁的破坏形式主要是基体的犁削和切削以及合金碳化物的断裂引起的磨损失效。实验室自主研发的7CrMnMoS易切削钢,需进行调质处理以期得到具有良好的综合力学性能并利于机加工的回火索氏体组织。本文设计旨在既保留回火索氏体组织又能细化晶粒的多次调质热处理工艺,以期使其耐磨性得到提高。通过销-盘、销-环实验对其磨料磨损性能进行了测试。结果表明,两种实验方法下,随着调质次数的增加,干、湿环境下7CrMnMoS的耐磨料磨损性呈增大趋势。利用单划痕模型对其做了较好的解释。除此之外,还对磨料磨损的机理进行了分析研究,结果表明磨料磨损的过程是微观切削、犁削、疲劳综合作用的过程。销-环情况下7CrMnMoS的干滑动磨损实验表明,干磨损条件下主要表现为剥层为主和氧化为辅的复合磨损形式。并通过对磨损面形貌、磨屑形貌、亚表层组织形貌、亚表层硬度分布的研究加以证实。结果还表明材料的干滑动耐磨性和磨损条件有着较大的关系。低载、低速下磨损量随着调质次数先增大后稍微降低。高载、高速下磨损量随着调质次数的增加而降低的趋势更加明显。出现上述现象的原因和磨损过程中材料强化机制的作用尺度效应有关。随着载荷和速度的增大,磨损亚表层变形层深度增加,细晶强化的效果表现的更明显。更多还原

【Abstract】 Because of the high wear resistance to abrasives high chromium white cast iron is widely used in foundry equipments. In this paper, imported high chromium white cast iron pipe with perfect wear resistance was used as objective material. In order to interpret the reason to its high wear resistance, microstructure of the white cast iron was systematically studied. Metallurgical structure research and XRD research both demonstrate the high Cr white cast iron with high hardness martensite and alloy carbide rods. Pin-on-disk testing shows its relative wear resistance is 2.5 times higher than normalized 45# steel. Moreover, according to the research on wear surface morphology and wear particle morphology, the wear failure of high chromium is main caused by substrate micro-cutting and micro-ploughing and the fracture of alloy carbide rods.Free-cutting steel 7CrMnMoS independently researched and developed by laboratory was used as experimental material. As good machining performance and good mechanical properties is needed, 7CrMnMoS was quenched and tempered as tempered sorbite as the final microstructure. In this paper, repeated quenching and tempering processing was used to not only refine the grain size and but also keep the microstructure as tempered sorbite. Good wear resistance is also desired to be obtained by the processing. And then, pin-on disc and pin-on-ring machine were both used to test wear loss. And the results show that no matter dry or wet conditions the wear resistance of 7CrMnMoS increases with the quenching and tempering numbers. Single scratch experiment model was used to give a good explanation. In addition, abrasive wear mechanism was also studied, and micro-cutting, micro-ploughing and micro-fatigue were all discovered during wear process.Pin-on-ring dry sliding wear test results indicate that the wear mechanism is plastic deformation dominated and oxidation- supplemented combined wear mechanism. This mechanism was later proved by wear surface morphology, wear particle morphology, subsurface microstructure, subsurface hardness distribution. The results also show the dry sliding wear resistance has close relationship with wear condition. Under the condition of low load and speed, wear loss increases with the quenching and tempering numbers and then slightly decreases. When the load and speed reach a high level, wear loss obviously shows decreasing trend with the increase of quenching and tempering numbers. The reason to the results we observed is that the size effect strengthening mechanisms works during the wear process. With the increase of load and speed, the thickness of the worn surface caused by wear process will increase and the grain refinement strengthening mechanism will work effectively.更多还原