| High speed steel (HSS) have been mostly used as cutting materials, die materials andwear resistant materials, due to their high hardness, high wear resistance, high cuttingperformance and high temperature hardness, strength. As the development of ceramics, metalceramics and cemented carbides, the emergence of the difficult-to-machine materials and thehigh hardness materials, higher request on the hardness，toughness and wear resistance ofhigh speed steel is put forward. Particle reinforced high speed steel composites (PRHSSCs)combine both the characteristics of high speed steel matrix and the ceramic particles, whichexhibits excellent mechanical properties, high wear resistance, superior thermal conductivityand chemical stability. Therefore, the HSS composites not only traditionally use in the cuttingfield, but also can use as traditional wear resistance structure materials. Thereby, differentcontents of titanium carbide particles (TiC_p) were added to the powders of M2HSS (vt%) inthis study. The fabrication process, microstructures, mechanical properties and friction andwear of the M2HSS composites were investigated.First, xTiC_p/M2HSS (x=5,10,15,20) composite powders were prepared by highenergy ball milling, analyzed the effects of high energy ball milling on the morphology,particle size and microstructure evolution of the HSS composite powders, and then the effectsof TiC content on the morphology and microstructure evolution of the composite powderswere discussed. A relative small particle size, a narrow particle size distribution and a uniformdistribution of TiC particles were obtained. The results showed that average particles size ofthe composite powders decreased to20μm after20h of milling, and the particle sizedistribution was5~40μm. The squeezing and shearing of powders could be enhanced withthe addition of TiC particles in ball milling. It was scarcely effects of balling time and TiCcontent on the phase of the composite powders.The composite powders mentioned above were sintered by spark plasma sintering (SPS).The sintering densification performance was discussed as well as the effects of sinteringtemperature, pressure, holding time and TiC content on microstructures, mechanicalproperties and friction and wear of sintered composites were investigated. The results showedthat the densification process was made of4stages. The sintered composites contained Fe phase，M6C、MC and TiC phase and the TiC particles size was near200nm. When thesintering temperature ranged from960oC to1060oC, the density and the size of the carbides(M6C、MC） increased, while the hardness and the bending strength increased firstly andthen turned to decrease. When the temperature was1040oC, the density, hardness andbending strength increased with the rise of sintering pressure and holding time. The study alsoindicated that the density and bending strength of the sintered composites decreased with theincrease of TiC content, the hardness increased firstly and then decreased with the TiC contentincreasing. The observation of the facture morphology showed that the facture modescontained both ductile facture and brittle facture. It can be seen dimple and the facturemorphology showed obvious inter-grain-boundary facture characteristics.The research of friction and wear behavior of the TiC_p/M2HSS composites indicatedthat as the increasing of TiC content, the average friction coefficient increased, while the wearmass fell down firstly and went up and reached its minimum value of1.30×10-1mm3and2.91×10-1mm3when the content of TiC was10%, under the loading of300N and500N,respectively. When the TiC content is not more than10%, the composites of friction will bestable. Observation of wear tracks showed an abrasive wear mechanism in both M2HSS andTiC_p/M2HSS composites, and the wear mechanism of M2HSS including adhesivemechanism, the TiC_p/M2HSS composites wear mechanism contains fatigue mechanism whenthe TiC content was more than10%.According to the study, an optimal processing parameter was that sintering temperatureof1040oC, sintering pressure of50MPa, holding time of10min and TiC content of10%.The corresponding composite had excellent wear resistance performance and superiorcomprehensive mechanical properties with wear mass were1.30×10-1mm3and2.91×10-1mm3and average friction coefficient were0.312and0.298under the loading of300N and500N, respectively. The density, relative density, hardness and bending strength were7.74g/cm3,98.7%,58.9HRC,1512MPa, respectively. |
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