Preparation And Characterization Of Ti₂AlC/Cu Composite And Research Of Its Friction And Wear Behavior

Ternary laminated ceramics are also called MAX phase ceramics (M for transitionmetal element, A mainly for III and IV group elements, X for C or N), possess properties ofboth metals and ceramics due to their unique bonding, such as high modulus, good thermalconductivity, micro plastic deformation ability and high damage tolerance. And MAX phaseceramics have a certain degree of self lubricating performance because of their layeredstructure, thus making MAX phase potential material for structure and function application,and broad application prospect in the field of electrical friction area. Recent scientificresearch suggests that the ternary laminated ceramics can be outstanding reinforced inpreparation of metal matrix composites, whose mechanical properties and friction and wearperformance improve obviously. In engineering field, the feasibility of ternary laminatedceramic reinforced metal matrix composite materials used in high-speed railway ofpantograph slide and air foil bearing have been explored. At the same time, research aboutfriction and wear behavior of ternary laminated ceramics also gradually expands, and madesome progress.As a typical representative of211phases in the MAX phase ceramics, Ti2AlC succeedthe unique properties of ternary laminated ceramic, at the same time Ti2AlC have the lowestdensity among MAX family, as well as excellent oxidation resistance. However, reportsabout characterization and preparation of Ti2AlC reinforced metal matrix and friction andwear behavior of Ti2AlC block material are very limited. We will take homemade Ti2AlCprepared by combustion synthesis as reinforcement and commonly used metal Cu in electricfriction field as matrix to prepare composites and study their mechanical properties,microstructure, friction and wear performance. We will also study the friction and wearbehavior of the Ti2AlC alone. Mainly on the following aspects:Firstly, we focus on the stability of Ti2AlC in Cu, we study the phase composition andmorphology of organization through the preparation of Ti2AlC/Cu composites underdifferent temperature conditions to determine the hot-pressing temperature under whichTi2AlC particles remain stable. We find that reaction occurs under800oC, and at950oC,Ti2AlC completely decomposed to TiC, Cu spread to the layer TiC and formed ingredientslaminated organization, mechanical performance of composites improved significantly inthe test of compression.Under800oC, Ti2AlC/Cu composites with different Ti2AlC contents were prepared. Inthe test on the mechanical properties, electrical properties and properties of friction andwear behavior, we found that the addition of Ti2AlC obviously improved compression andtensile performance, conductive loss of composites is small, the friction and wear performance is also very good at the same time. Under lower content of Ti2AlCenhancement (5%~15%), composites showed ultra low friction coefficient and wear rateagainst bearing steel, but friction and wear performance deteriorated because of abrasivewear as Ti2AlC content further increased.In study of Ti2AlC friction and wear behavior, we take GCr15and Al2O3as frictionpairs respectively, and carry on test under the conditions of different vacuum degree, speedsand loads. In atmospheric environment, with the increase of sliding velocity, surface oxidefilm occurs gradually and works as lubricant, the friction coefficient and wear rate dropssignificantly to as low as0.25(GCr15) and0.46(Al2O3) respectively. But layer peeling offof Ti2AlC under low speed comes out and causes serious wear and tear, we think that theoxidation and eduction ofAl atoms under certain speed and load conditions may explain this.In the friction and wear behavior study under different vacuum of Ti2AlC, we found thefriction coefficient firstly rise and then decline as vacuum up, the lowest friction coefficientwas as low as0.19(GCr15) and0.42(Al2O3) respectively even lower than that under theconditions of the oxide film lubrication, this may be also related to Al atoms oxidation andeasier Ti2AlC interlayer sliding, while the variation of wear rate is quite different fromfriction coefficient, only related to vacuum condition and the relevance to the slidingvelocity significantly reduced.