低碳钢搅拌摩擦焊用摩擦头的失效研究

Failure investigation of tool for mild steel in friction stir welding

选用YG8硬质合金作为摩擦头材料进行低碳钢的搅拌摩擦焊试验。采用游标卡尺测量工具、X射线衍射仪和能谱仪等分析摩擦头在焊接过程中的主要失效形式。结果表明,YG8硬质合金摩擦头在低碳钢的搅拌摩擦焊过程中的主要失效形式为机械磨损、氧化剥落、搅拌针脆性断裂和轴肩变形失效等。引起失效的主要原因是摩擦头长时间的高温高压摩擦,导致粘结相Co分布不均匀或部分扩散流失,严重破坏了硬质合金的骨架模型;失效后摩擦头组织中出现了游离碳和硬脆相Co6W6C,减弱粘结相Co对基体相碳化钨的固溶强化作用,最终导致摩擦头的硬度、强度和耐磨性等下降。

The materials of tool for mild steel in friction stir welding is YG8 cemented carbide.In this paper,venire caliper,X-Ray diffractomer and energy disperse spectroscopy are used to analyze main failure forms of tool in welding.The research shows that the main failure forms of tool are mechanical wear,oxidation pee, brittle fracture of pin and failure of shoulder.Under the high temperature pressure power and long friction,the paper shows that the Cobalt of cemented carbides is uneven distribution or partly lost which badly damaged the skeleton model of cemented carbide.The new phase composition of failure tool such as free carbon and brittle phase Co6W6C lead to withdrawal of solution hardening of Cobalt for Tungsten carbide in cemented carbides,and the strength, hardness and wear resistance of tool are down.That is the important microscopic factor affecting the failure of tool.