磨粒磨损中基体表面形成复合材料层的作用机理及其影响因素的考察

An Examination of Mechanism and Influencing Factors of a Composite Material Layer Formed in the Abrasive Wear

在工程应用中，存在着较低硬度表面比较高硬度表面耐磨性更好的现象。为了弄清其原因，用固定磨粒和活动磨粒分别研究了磨损过程中较低硬度基体表面的强化效应；在给定的试验条件下，固定磨粒和活动磨粒都能够在试件表面形成磨粒－铁复合材料层，从而使表层材料的硬度提高、耐磨性改善、使用寿命延长，其中固定磨粒的粒度越大，越有利于复合材料层的形成；活动磨粒造成的增重效果更加明显，而且复合材料层也比较厚。复合材料层的形成机理主要为磨粒嵌入与破碎，并在其它大磨粒引起的试件表层材料变形过程中与铁基体混合。能谱分析发现，无论是固定磨粒还是活动磨粒，两者在磨损过程中形成的复合材料层所含磨粒／铁的分子混合比均约为２：１，超过此值后将不能保持铁基体的连续性而造成复合材料层的剥落。因此，在工程实际中，对于那些并非很恶劣的磨粒磨损工况的场合，利用这种磨粒引起基体表面强化的手段，可以在很经济的条件下使机械零部件获得更长的使用寿命。

A phenomenon is present in the industrial applications that the surface with lowerhardness shows a better wear-resistance than the surface with higher hardness. In order to clarify itsmechanism,the surface strengthening effect of a substrate with lower hardness in wear process wasinvestigated by using the fixed and free abrasives separately. Under the given test condition,boththe fixed and free abrasives can form an abrasive/iron composite mate rial layer on the surface ofspecimens,in consequence,their hardness and wear-resistance can be increased and their servicelife can be lengthened. The bigger the fixed a brasives,the casier the formation of this compositematerial layer. The effect of in creasing weight is m ore obvious for the free abrasives,and thethickness of the composite lay er is al so larger.The formation mechanism of composite layer ismainly due to the embedmen t and crack of abrasives and mixing with the iron substrate in thedeformation process induced by other big a brasives.The analvsis by EDX found that the ratios ofabrasives to iron in the composite layers are 2:1 regardless the abrasives are fixed or free,becausethe composite layer will peel off due to the damage of continuity of iron substrate when this ratiowas surpassed.Therefore,this surface strengthening measure by forming a composite material layercan be employed in practice very e conomically for lengthening the service life of machinecomponents in the condition of not too severe abrasive wear.