目的：研究微弧火花渗碳对定向凝固高温合金 DZ125 L 表面再结晶的控制效果。方法对DZ125 L合金进行吹沙变形处理,以石墨棒为碳的来源,通过微弧火花渗碳工艺在吹沙表面进行渗碳处理后,与直接吹沙的试样一起进行热处理,通过光学显微镜( OM )、扫描电子显微镜( SEM )、X 射线衍射( XRD)等手段表征组织结构。结果与合金直接吹沙产生的表面再结晶相比,经过微弧火花渗碳+吹沙处理的样品,表面再结晶深度只有直接吹沙处理样品的60%。 XRD分析表明,微弧火花渗碳处理后,合金表层产生了TiC和( Cr,Mo)23 C6等碳化物。能谱分析表明,渗碳样品截面外表层富集Ti、Mo、W、Cr、C等元素,产生了大量碳化物,进一步阻碍了再结晶晶界的迁移。微弧火花渗碳强化了合金表层,使合金在吹沙处理时产生的变形层较浅,抑制了再结晶表面形核。结论通过微弧火花渗碳工艺可以有效抑制定向凝固高温合金的再结晶。
Objective To investigate the control effect of micro-arc carburization on the surface recrystallization ( RX) of a di-rectionally solidified superalloy DZ125L. Methods After being deformed by shot-peening, the DZ125L samples were carburized by micro-arc carburization with graphite bars. And then they were heat treated with those samples that were shot-peened directly. Mi-crostructure was characterized by optical microscopy ( OM) , scanning electron microscopy ( SEM) , and X-ray diffraction ( XRD) . Results Compared with surface recrystallization produced by direct shot-peening, the depth of surface recrystallization after micro-arc carburization combined with shot-peening accounted for only about 60% of samples without micro-arc carburization. The XRD analysis indicated that plenty of TiC and ( Cr,Mo) 23 C6 were formed on the surface layer of alloy after micro-arc carburization treat-ment. Enrichment of Ti, Mo, W, Cr and C was found by energy dispersive spectroscopy ( EDS) analysis on the surface layer of carburization treated samples, which further indicated that plenty of carbides were formed. These carbides retarded the migration of RX grain boundary. Furthermore, micro-arc carburization strengthened the surface layer of alloy and the carbides covered the sur-face of the alloy, which made the deformed layer become smaller and suppressed the RX nucleation on the surface, and resulted in the smaller RX depth finally. Conclusion Therefore, RX can be suppressed effectively by micro-arc carburization treatment.
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