时效对Fe基合金激光重熔层组织和性能的影响

Effect of aging on microstructure and properties of laser remelted layer of Fe-based alloy

利用场发射扫描电镜、透射电镜、X射线衍射仪和电化学工作站等,对比分析了Fe基合金原始热喷焊层、在500℃经不同时间时效处理后激光重熔层的组织和性能。结果表明,火焰喷涂后的热喷焊层组织较粗大,经激光重熔后组织明显细化,由较细小的树枝晶间均匀分布着层片状共晶组织构成;随时效时间的增加,重熔层中距离共晶组织较近的柱状晶球化,基体中Cr7C3、Cr23C6型碳化物进一步析出,弥散分布在枝晶间层片状共晶组织上;时效6 h所获得的激光重熔层组织硬度最大,可达507 HV0.5,随时效时间继续增加,硬度有所下降,但仍高于未经时效处理时的激光重熔层组织硬度;热喷焊层经激光重熔,耐腐蚀能力显著提高到最强,时效6 h的激光重熔层耐腐蚀性降低不明显,时效48 h的激光重熔层的耐腐蚀性则明显降低。

Microstructure and properties of thermal spraying welded layer and laser remelted layer with different aging treatment at 500℃ of an Fe-based alloy were compared and analyzed by using field emission scanning electron microscope(FE-SEM),transmission electron microscope(TEM),X-ray diffractometer(XRD)and electrochemical workstation.The results show that the microstructure of the thermal spraying welded layer after flame spraying is relatively coarse,which is markedly refined as composed of fine dendrites with lamellar eutectic evenly distributed in between after laser remelting.With the increase of aging time,columnar crystals closer to the eutectic structure in the remelting layer start to spheroidize,Cr7C3 and Cr23C6 carbides are further precipitated in the matrix and distribute in the lamellar eutectic structure between the dendrites.The hardness of the laser remelting layer aged for 6 h is the highest,as up to 507 HV0.5.With the aging time continues to increase,the hardness decreases,but it is still higher than that of the laser remelted layer without aging.After laser remelting,the corrosion resistance of the thermal spraying welded layer is significantly improved to the maximum,and that aged for 6 h is not significantly reduced,while that aged for 48 h is significantly reduced.