Mechanical Properties And Wear Mechanism TiC/TRIP Steel Composites

In this paper, TRIP steel powder and TiC powder were used to fabricated theTiC/TRIP steel matrix composites with different TiC content via hot pressingsintering with the condition of1150℃,30MPa,1hour, which was protectedunder N2atmosphere. In order to systematic research the influence of TiC contentand heat treatment to mechanical property of TiC/TRIP steel composites, we usedthe X ray diffraction (XRD), scanning electron microscopy (SEM), method ofthree point bending beam and unilateral incision to characterize the properties ofthis composites. In addition, we also set Si3N4ceramic ball as friction pair todiscuss the influence of TiC content and heat treatment to friction and wearproperties of TiC/TRIP steel composites.The result indicated that the density, bending strength and fracturetoughness of TiC/TRIP steel matrix composites decreased with the increase ofTiC content. The maximum value of density, bending strength and fracturetoughness was97.7%,1079.8MPa and7.51MPa·m1/2, which appeared withoutthe addition of TiC. In contrast, the hardness enhanced with the increase of TiCcontent and the maximum value reached4.40GPa under TiC content of40wt.%.After heat treatment, the change trends of the density, bending strength andfracture toughness of TiC/TRIP steel composites were the same as those beforeheat treatment. Comparing the TiC/TRIP steel composites before and after heattreatment, when TiC content was less than10wt.%, the bending strength andfracture toughness enhanced, and the trends could be opponent with the TiCcontent larger than10wt.%.The XRD analysis showed that the TiC/TRIP steel composites wascomposited with α-Fe, γ-Fe(main composition of TRIP steel) and TiC phasebefore heat treatment, which indicated that there was no chemical reaction inpreparation process and the two phases exhibited excellent chemical compatibility. After heat treatment, the TiC/TRIP steel composites wascomposited with α-Fe phase and TiC phase which indicated that the γ-Fe phasetransferred into α-Fe phase.The SEM of fracture morphology indicated that the rupture mode of TiC andTRIP steel in TiC/TRIP steel composites were intergranular fracture, othertranscrystalline fracture and ductile fracture respectively. The rupture mode afterheat treatment is the same as that before heat treatment, but the ductile fracture ofTRIP steel decreased with the increasing of TiC content, which resulted in thedecrease of fracture toughness and bending strength after heat treatment.The friction and wear performance of TiC/TRIP steel composites withdifference TiC content were tested under the same condition of fixed load, slidingspeed and time. Those indicated that with the increasing of TiC amount, frictioncoefficient of composites present a trend which was first decreased and thenincreased, and the wear rate and wear diameter of ceramic ball presented a trendcongeniality. With the TiC amount of30wt.%, the friction coefficient, wear rateand ball wear diameter of both before and after heat treatment reached theminimum diameter (0.531,2.810-7g/N m,0.72mm and0.523,2.510-7g/N m,0.71mm respectively).The friction and wear mechanism of TiC/TRIP steel composites with bothbefore and after heat treatment were abrasive wear and fatigue wear. As theadding TiC played a role of grits, abrasive wear became the most serious wearform. But with the increasing of TiC content, fatigue wear occurred easily andthe maximum of abrasive wear appeared with TiC content of40wt.%.