B元素对Fe-Cr-C系耐磨堆焊合金组织和耐磨性的影响

Effects of boron on microstructures and wear resistance of Fe-Cr-C system hardfacing alloys

关键词:  Fe-Cr-C堆焊合金  药芯焊丝  微观组织  耐磨性

Key words:  Fe-Cr-C hardfacing alloys  flux cored wires  microstructures  wear resistances

摘要:

采用直径为1.6 mm的细径药芯焊丝,利用CO₂气体保护焊堆焊的方法制备了含有1.0%~3.0%C(质量分数),15%~20%Cr,0%~2.0%B的高铬堆焊合金.研究了B₄C含量对堆焊合金的硬度及耐磨性的影响.结果表明,堆焊合金的硬度从57.1 HRC增加到65.2 HRC,硬度提高14.2%;堆焊层合金的相对耐磨性从3.5倍提高到18.0倍.借助光学显微镜、扫描电镜和X射线衍射等微观分析方法,研究了堆焊合金的显微组织及碳化物分布形貌.结果表明,堆焊合金的显微组织主要由铁素体+奥氏体+(Fe,Cr)₇C₃组成,加入B₄C可显著改善堆焊合金层基体组织,使碳化物(Fe,Cr)₇C₃数量增加且呈弥散分布.

Abstract:

Fe-Cr-C based hardfacing alloys were produced by the CO₂ gas shielded welding process utilizing the flux cored wires of 1.6 mm in diameter on low-carbon steel substrates. The hardfacing alloys contained the carbon contents in the range of 1.0%-3.0%,chromium contents of 15%-25%,boron contents of 0%-2.0%. The effects of boron carbide contents on the microhardness and wear resistance of the hardfacings were studied. The results show that the hardness increased from 57.1 HRC to 65.2 HRC as the boron contents reaches up to 2.0%. Compared without boron addition,the hardness increases by 14.2% times. The relative wear resistance increases from 3.5 to 18.0 times. By using of the optical microscope (OM),scanning electron microscope (SEM) and X-ray diffraction (XRD),the microstructures and distribution of carbides in the matrix were investigated. The microstructures of metallic matrix are composed by ferrite, austenite,(Fe,Cr)₇C₃,Fe₂B,etc. The additions of boron carbide in the wires can improve the microstructure of the matrix of the hardfacing alloys and the quantities of the carbides. The distribution of (Fe,Cr)₇C₃ particles are uniformly dispersed.