碳化硼对粉/丝复合堆焊高硼铁基合金组织结构的影响

为了探讨合金元素B,C对高硼铁基堆焊合金组织结构、裂纹敏感性的影响,采用粉/丝复合堆焊技术配合不同B₄C含量合金粉体制备高硼铁基堆焊合金,通过显微组织结构、微区成分、显微硬度及宏观硬度试验检测,分析不同B,C元素含量及配比的堆焊合金组织与性能. 结果表明,高硼铁基堆焊合金由α-Fe,Fe₂B,Fe₃(C,B)相组成,随着B₄C的添加,初晶岛状α-Fe消失,菱形初晶Fe₂B、粒状Fe₃(C,B)析出,鱼骨状、条状共晶状组织α-Fe+Fe₂B体积分数趋于减小并消失,菊花状α-Fe+Fe₂B+Fe₃(C,B)包晶组织成为堆焊合金的主体. 高硼铁基合金中硼、碳的含量及配比是影响堆焊合金组织结构、裂纹敏感性的原因之一,约30%合金粉体(含35%硼铁粉、5%B₄C)配合约70%H08Mn2Si焊丝获得的堆焊层,可有效抑制堆焊裂纹的出现,并可获得稳定的高硬度值66 HRC.

Influence of BC on microstructure of high boron content iron-based alloy in hybrid powder/wire overlay welding

In order to study the influence of the element of boron and carbon on the microstructure and cracking sensitivity of the high boron content iron-based overlaying weld, the hybrid powder/wire overlaying weld technology was used to prepare the coating by adding different content of B4C. The structure and the mechanical performance of the coating were studied by the microstructure observation, micro zone element analysis, micro hardness and macro hardness. Results showed that the high boron content iron-based alloy consisted of α-Fe, Fe₂B and Fe₃(C,B) phase. With the increase of the content of B4C, the primary land-shape α-Fe began to disappear and the diamond-shape primary Fe₂B and granular Fe₃(C,B) began to precipitate. The volume fraction of the fish bone shaped and lath shaped eutectic microstructure (α-Fe+Fe₂B) was gradually reduced and finally disappeared. The main microstructure was characterized with flower-shape α-Fe+Fe₂B+Fe₃(C,B) peritectic structure in the overlaying weld. The content of boron and carbon and their ratio are the the key factor affecting the microstructure and the cracking sensitivity. The overlaying welding consisted of about 30% alloy powder (including 35% boron iron and 5% B₄C) and about 70% H08Mn2Si welding wire could effectively restrain the initiation of cracking. The hardness could reach a stable value of 66HRC.