| Iron-based powder metallurgical (PM) components are put into use mostly in the kind ofPM materials, but they are more and more difficult to meet the requirements of usage with thedevelopment of the modern industry, science and technology. Therefore, higher request on thecomprehensive performance of this kind of materials is put forward. Particle reinforced metalmatrix composites (PRMMCs) combine the characteristics of metal materials with goodthermal stability, ductility and ceramic particles with wear resistance and high temperatureoxidation resistance. Thereby, in order to fabricate the materials with excellent comprehensiveperformance, some contents of tungsten carbide particles (WCp) were added to the powders ofFe-2Cu-2Ni-1Mo-1C (wt%) in this study. The fabrication process, microstructures andmechanical properties of the iron-based PM materials were investigated.First, Fe-2Cu-2Ni-1Mo-1C-xWC (x=0,5,10,15,20) powders were prepared by ballmilling, and then the topography, phase composition and thermal characteristic of the milledpowders were characterized by the methods of SEM, XRD and DSC, respectively. The resultsshowed that the grinding and crushing of powders could be enhanced with the addition of WCparticles in ball milling. After40h ball milling, fine grains of powders could be obtained,some elements (e.g. Cu, Mo and C) were dissolved into the α-Fe lattice by means of diffusionforming the crystallology supersaturated solid solution. A solid phase transition of the milledpowders was turned up at the temperature range of680~770oC.The milled powders mentioned above were sintered by spark plasma sintering (SPS).The sintering densification process was discussed as well as the effects of heating rate,sintering temperature and WCpcontent on microstructures and mechanical properties ofsintered alloys were investigated. The results showed that shrinkage rate shaked up obviouslywith the increase of heating rate and/or WCpcontent. It meaned that higher heating rate and/ormore WCpcontent were favorable to the densification. The alloy was mainly composed offerrite, pearlite, austenite and bulky WC particles. When the sintering temperature rangedfrom750oC to1000oC, the density increased first and then turned to decreasing. When thetemperature was850oC, the density increased significantly with the increase of WCpcontent,but more WCpcontent was unfavorable to the hardness, bending strength (BS) and the friction stability. Fracture mode and wear mechanism of the alloys were characterized as dimplecoalescence and cleavage, abrasive wear and adhesion wear, respectively.In order to further improve the comprehensive performance of sintered alloys, one of thebetter alloys Fe-2Cu-2Ni-1Mo-1C-15WC was chosen to be quenched and tempered atdifferent temperatures. Effect of tempering temperature on microstructures and mechanicalproperties of the alloys were researched. The results showed that some martensite existed inthe alloys after tempering (180oC). The alloy was mainly composed of pearlite,residualaustenite, martensite and WC particles. Compared with alloys without heatingtreatment, the hardness and BS of the tempered alloys were higher, while the average frictioncoefficient and abrasion loss were lower. It was implied that the friction stability of thetempered alloys was improved obviously. With the increase of tempering temperature, thealloys were constituted of pearlite, residualaustenite and WC particles. The hardness dropedmonotonously, while BS decreased firstly and then increasd. And the friction coefficient andabrasion loss increased.According to the study, an optimal processing parameter was that sintering temperatureof850oC, heating rate of temperature100oC/min, WCpcontent of15%and temperingtemperature of180oC. The corresponding alloy had good comprehensive mechanicalperformance with the density, relative density, hardness, BS, average friction coefficient andabrasion loss were8.46g/cm3,99.56%,61.1HRC,1817MPa,0.3145and0.1mg,respectively. |
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