Study of the matrix-carbide eutectic compound in carbon-rich 30wt.% cr-containing nickel, cobalt and iron-based hard alloys

Some of the wear-resistant tools or coatings are based on Ni, Co or Fe and contain very high carbon contents for promoting high volume fractions of carbides in the microstructures.Among them fine eutectic carbides and coarse pro-eutectic carbides do not induce the same properties for the alloys in terms of hardness, wear resistance and impact toughness. Thus itmay be important to knowinwhich proportions they are in the eutectic formand as coarse carbides. Eighteen 30wt.%-containing nickel-based, cobalt-based and iron-based alloys with six different carbon amounts (from2.5 to 5.0wt.%) previously elaborated by high frequency induction melting were metallographically characterized in their as-cast condition and after heat-treatments at high temperature. More precisely their microstructures were quantified by image analysis in order to separate the surface fractions of the pro-eutectic phases (dendrites of matrix or carbides) fromthe eutectic compound. These results were thereafter compared to the ones issued from Thermo-Calc calculations concerning the eutectic solidification part.