| Powder metallurgy is a near-net forming technology with less or non-machining. It has the advantages of saving raw materials, high efficiency, non-polluting, less investment and so on. The most commonly used metal powder are iron and copper powder in powder metallurgy process. The application of iron-based powder is becoming increasingly widespread in the field of power metallurgy because of the low price of iron powder, high strength after pressing and sintering, simple production process. The anti-friction performance of traditional iron-based powder metallurgy is good, but the strength is lower. And iron-based powder metallurgy structural parts have good mechanical properties, but poor friction reducing effect. For this phenomenon, this thesis chooses the iron-based powder metallurgical materials with porosity from 13%to 20%. Then the materials are on melt infiltration treatment. The tin-copper and bismuth-copper powder having a certain friction-reducing effect and lower melting point than the matrix skeleton are used as infiltration agent. Then infiltrating into the three sets of base material prepared. The infiltration microstructure, mechanical properties and friction and wear properties of materials in before and after infiltration are studied. The Research results indicate:(1) Using the AE alloy powder as based material, then the matrix materials with density of 6.3,6.5 and 6.8 g/cm3 are prepared by powder metallurgy process. As the density increases, the hardness and crushing strength gradually raise. But the oil content is gradually reduced and the friction reducing effect is also gradually deteriorated. When progressive loading friction and wear tests, the density of 6.3 g/cm material has relatively good ability of anti-bite and its scratch load reaches 2800 N.(2) The porosity is decreased and the compressive strength increases, but the effect of reducing friction is poor when the Iron based materials are infiltrated with tin and copper powder. The matrix material with density of 6.3 g/cm3 are infiltrated with tin and copper infiltration agent containing of 90%copper, the compressive strength reached 992 MPa, an increase of 71%, anti bite capacity and wear resistance also has certain improvement.(3) After iron-based material is totally infiltrated with bismuth, the increase of the compressive strength are not obvious, but the anti adhesion ability was increased and the load was obviously increased. When the load is high, the friction-reducing effect of low-melting after softening bismuth playing together with the lubricants is better than before the infiltration as materials with more bismuth content. And it is useful to improve the anti-seizure and anti-abrasion performance.(4) After adding the copper into the bismuth agent, the increasing of compressive strength of the sample after infiltration is more obvious. At the same time, as the content of bismuth in the sample is decreased, it leads to the reduction of the antifriction effect. When the load is more higher, the friction coefficient of matrix material has little difference compared to the before and after infiltrating matrix material whose density is 6.5 g/cm3 with bismuth and copper infiltration agent containing 60% copper. But the anti abrasion and anti seizure ability compared with the matrix material with density of 6.5 g/cm3 are significantly improved. Its crushing strength is 1051 MPa, an increase of 72%, and its scratch load is 3200N, an increase of 33%. |
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