Influence of Cr content on microstructure and hardness of Fe-B-C wear-resistant alloy surfacing layer

In order to inhibit the microcracks in the hard phase Fe2B of the high B Fe-based wear-resistant surfacing alloy and improve the wear resistance of the surfacing alloy layer,different content of Cr was added to the Fe-B-C based wear-resistant surfacing alloy to study influence of Cr content on morphology,phase composition and hardness of the surfacing layer.Method of adding different content of micro-carbon ferrochromium powder was adopted in the experiment,plasma powder surfacing process was used to prepare high-B Fe-based surfacing alloys with different Cr contents on the Q235 steel plate,and morphology,phase composition and hardness of the surfacing layer were analyzed through methods of optical microscope,XRD,SEM,EDS and Rockwell hardness.The results showed that the surfacing alloy layer was composed of primary Fe2B phase and eutectic structure α-Fe+Fe3(C,B)with no addition of micro-carbon ferrochrome powder,and new primary crystal phase Fe1.1Cr0.9B0.9 with 30% addition amount of micro-carbon ferrochromium powder.Cr element had effect of promoting precipitation of the hard phase Fe2B in the surfacing layer,and could effectively inhibit generation of microcracks in the primary Fe2B phase.Hardness of the surfacing layer increased with the increase of Cr content,which was as high as 65.5 HRC with 55% addition amount of micro-carbon ferrochromium powder.Highlights:A kind of high B Fe-based wear-resistant surfacing alloy with high hardness and crack resistance was designed.The formation regularity of microstructure in surfacing alloy was clarified,and modification mechanism of Cr on surfacing alloy was revealed.In surfacing alloy,ear-like primary crystal phase Fe1.1Cr0.9B0.9 was wear-resistant skeleton and eutectic microstructure α-Fe+M3(C,B)was the supporting phase.The problem of high brittleness of high B Fe-based surfacing alloys was effectively solved by coordination between the two phases.