The Study On Mechanism Of Rear Earth Elements In Iron Based Powder Metallurgical Friction Material

The emphasis of this thesis is the study on the effect and mechanism of mechanical and friction performance caused by rare earth elements in iron based powder metallurgical friction material. Then, the model of the mechanism engendered those effects was founded.The principle part of composition in this research was the composition of FMPS iron based powder metallurgical friction material.At first, one kind of rare earth was pick out from four different types of material and the optimized interpolative quantity was ascertained. According to the result of mechanical performance testing, the research focused on specimens that had been added class A rare earth alloy.The methods of microscopic analysis included quantitative metallographic analysis, SEM, ED AX, XPS. The result is: the rare earth exerted adequately while its' amount was optimum, the specimen obtained best mechanical performance at the same time; and when the amount of rare earth was excessive, non-dissolve rare earth appeared. The non-dissolve rare earth could evoke MoSa which was added as lubricant, and made it decompose. The decomposition of MoS2 could create atomic S, and then atomic Swould combine with Mn which was alloy element and turned into MnS. So the mechanical performance of specimen decreased.Two supplemental experiments were carried out for the sake of in-depth researching on mechanism of MoS2's decomposition. The conclusion of the two supplemental experiments proved that MoS25s decomposition needs three conditions. The first was existing of the non-solution RE, the second was existing of Pb, the last was the specimens' sintering temperature exceed Tc. The rare earth acted as similar 'catalyst' and Pb acted as similar 'medium' during the reaction. According to that, the "Pb pool" mode was put forward. EDAX, XPS, thermodynamical analysis and calculation showed that outcomes of "Pb pool" were Mo and MnS.Small specimens' frictional experiment, one-third scale frictional experiment and trim size frictional experiment were carried out in this research. The result of frictional experiments showed that the rule of all the tribological parameters's variational trending under different conditions during three frictional experiments was consistent with that of mechanical performance and microscopic analysis very much. So, there had an optimized interpolative quantity while adding rare earth into FMPS iron based powder metallurgical friction material, and then the material got more better mechanical performance and frictional property.