预置硅铁对高铬堆焊合金组织及耐磨性的影响

Effects of presetting ferro-silicon content on microstructure and abrasion resistance of high-chromium hardfacing alloys

共晶碳化物形态影响高铬合金的致脆性。采用药芯焊丝自保护明弧焊方法熔化预置粉末形成高铬堆焊合金,借助金相显微镜、X射线衍射仪及扫描电子显微镜等手段,考察了预置硅铁含量对其组织和耐磨性的影响。结果表明,随着预置硅铁增加,合金初生M7C3相（M代表Fe、Cr、Mn等金属元素）由板条状转变为六方块状弥散分布,其四周共晶碳化物形态由片状转变为颗粒状,显著不同于常规层片状共晶。焊道预置药芯焊丝熔敷金属质量40%~60%的合金粉末,在焊接热输入总量不变的条件下,不仅可使单位熔敷金属的热输入量减小28%~38%,降低焊缝残余热应力,而且使熔敷效率提高36%~55%,并改善了共晶碳化物形态。合金磨损失重随预置硅铁增加而梯次减小,耐磨性提高了40%;该合金磨损机制包括磨粒的显微切削和显微剥落2种,其显微剥落量因共晶碳化物形态改善而持续减小。

The morphology of the eutectic carbides in the high-chromium alloys has an effect on their embrittlement.High-chromium hardfacing alloys were deposited by the method of flux-cored wire self-shielded open arc welding with presetting alloying powders on weld beads.The effects of presetting ferro-silicon content on their microstructure and abrasion resistance were investigated by optical microscopy（OM）,X-ray diffractometer（XRD）together with scanning electron microscopy（SEM）.The results show that,with the continuous addition of ferro-silicon powders,the shape of primary M7 C3 carbides transits from rod-like shape to hexagonal block-like shape in dispersion distributing state,M represents such element as Fe,Cr,Mn.Those surrounding eutectic carbides change from strip shape into granular shape,which is deliberately different from conventional eutectic one.On the condition of invariable weld input gross heat,presetting alloying powders on weld beads with the unit amount in equivalence with 40%to 60% of the mass of flux-cored wire deposited metals in need,can reduce 28%to38% heat input on unit deposited metals and decrease the residual heat stress of weld beads.Presetting alloying powders not only leads to the 36% to 55% boosting of hardfacing deposition efficiency,but also improves the morphology of the eutectic carbides.Their wear mass loss reduces continuously with the increase of ferro-silicon powders and the abrasion resistance improves by at least 40%.Their wearing mechanism includes the micro-cutting and micro-spalling.The micro-spalling amount is reduced persistently for the improvement of the morphology of eutectic carbides.