Cr含量对Fe-B-C系耐磨合金堆焊层组织和硬度的影响

为了抑制高硼铁基耐磨堆焊合金硬质相Fe2B内部的显微裂纹，改善堆焊合金层的耐磨性能，向Fe-B-C系耐磨堆焊合金中添加不同含量的Cr，研究Cr含量对堆焊层组织形貌、物相组成及硬度的影响。试验采用添加不同含量微碳铬铁粉的方式，利用等离子粉末堆焊的工艺，在Q235钢板上制备具有不同Cr含量的高硼铁基堆焊合金，通过光学显微镜、XRD，SEM，EDS及洛氏硬度等方法对耐磨堆焊层的组织形貌、物相组成及硬度进行了分析。研究结果表明，未添加微碳铬铁粉时，堆焊合金层由初晶Fe2B相和共晶组织α-Fe+Fe3(C,B)组成；当微碳铬铁粉的添加量为30%时，出现新的初晶相Fe1.1Cr0.9B0.9；Cr元素具有促使堆焊层组织硬质相Fe2B析出的作用，并且能有效抑制初晶Fe2B相显微裂纹的产生；堆焊层的硬度随Cr含量的增加而增加，当微碳铬铁粉添加含量为55%时，硬度高达到65.5 HRC。创新点： 设计了一种高硬度、高抗裂性的高硼铁基耐磨堆焊合金材料。阐明了堆焊合金组织的形成规律，揭示了Cr对堆焊合金的改性机理。堆焊合金以麦穗状初晶相Fe1.1Cr0.9B0.9为耐磨骨架，共晶组织α-Fe+M3(C,B)为支撑相，两者相互协调配合，有效解决了高硼铁基耐磨堆焊合金的脆性过高的难题。

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.