碳含量对自保护明弧高铬堆焊涂层性能的影响

Effect of Carbon Content on Properties of Self-shielded Open Arc Hardfacing Coating

采用药芯焊丝明弧自保护焊方法制备了含有2.0%～4.5%C、21%～23%Cr、1.5%～1.7%Si、0.2%～0.3%B（质量分数）的耐磨涂层,对其显微组织及耐磨性进行了表征,并考察了碳含量的影响。结果表明,其显微组织由酌-Fe＋α-Fe＋M7C3＋M3（C,B）＋Si5C3＋Fe4N等组成。随碳含量提高,胞状富铬酌-Fe基体数量逐渐减小,直至消失,而位于晶界区域的硬质相体积分数增加。当碳含量为3.5%时,出现15～40μm六边形初生M7C3相颗粒,Fe4N相因石墨氧化形成保护气体量增加而下降。此外,湿砂耐磨性试验结果显示,堆焊涂层磨损为磨粒微切削机制为主,但无明显的塑性变形痕迹,其耐磨性不仅取决于其初生M7C3相数量,还与其共晶组织中二次M7C3数量和形态相关。

Wear-resisting coating containing 2.0%-4.5%C, 21%-23%Cr, 1.5%-1.7%Si, 0.2%-0.3%B（mass fraction）was deposited by a method of flux-cored wire self-shielded open arc hardfacing. Microstructural characterization and abrasion testing were performed as well as the research on the effect of carbon content. The results show that the microstructure is consists of γ-Fe, α-Fe and hard phases such as M7C3, M3（C, B）, Si5C3, Fe4 N etc. With the increase of carbon content, cellarγ-Fe matrix reduces gradually until entirely disappears and the volume fraction of hard phases distributing in the grain boundary increases. At 3.5%C, some 15-40 micron hexagonal primary M7C3 grains appear, but the volume fraction of Fe4 N phase decreases due to the reinforcement of shield gas provided by the oxidation of graphite. Furthermore, the results of wet sand rubber wear tests indicate that the main mechanism of material wear removal is micro-cutting of abrasive particles without plastic deformation traces. Abrasion resistance not only depends on the volume fraction of primary M7C3 grains, but also is related with the size and volume fraction of secondary M7C3 grains contained in the eutectic.