Mechanical response and wear resistance of fe C-CR alloys

This research is tailored to reach compromise between the abrasive wear resistance andtoughness of the high Cr white cast iron to suit the individual application requirements. Inthis study, the abrasive wear behavior of a group of high Cr white cast irons as related totheir microstructure was investigated against 80 mesh AL203 abrasive papers. Six differentalloys of high Cr cast iron with a different chemical composition in the as-cast and heattreated conditions were tested at constant speed under various loads of 15, 30 and 45 N. Thedestabilization heat treatment at 950°C for one hour and a half produced significantimprovements in both hardness and abrasive wear resistance due to the formation ofsecondary carbides in a martensitic matrix surrounded by a network of M7C3 carbides.Subcritical heat treatments at 400°C and 500°C on the destabilized alloys gave little changesin both hardness and wear resistance without any indications to secondary hardening owingto low Mo content. These properties deteriorate significantly after tempering above 500°Cdue to the decomposition of martensite to ferrite/carbide aggregates. No significant changescould be detected in the microstructure of the alloys after subcritical heat treatments by anoptical microscope.Experimental results of this study showed that the alloy W2 with lower Cr/C ratioexhibited the lowest abrasive wear loss while the alloy WI with higher Cr/C ratio exhibitedthe highest abrasive wear loss. from the microstructure observation, it was noted thesignificant influence of Cr/C ratio ( specially with small Mo addition) on the type of thematrix structure in the as-cast condition. Higher Cr/C ratios with small Mo content ( i.e.0.5%) promoted austenitic matrix microstructure in the as-cast condition rather than pearliticmatrix. The differing of responses of the investigated alloys to the destabilization heattreatment at 900°C could be related to Cr/C ratios, where the alloys with lower Cr/C ratiosproduced substantial increases in hardness as compared to other alloys.