激光重熔和时效处理的镍基合金热喷焊层组织和性能的研究

Research of Microstructure and Properties of Ni-based Alloy Hot Sprayed-welding Layers by Laser Remelted and Aging Treatment

利用金相显微镜、扫描电镜和X射线衍射仪等分析手段,重点研究激光重熔镍基合金热喷焊层经不同时效工艺处理后的组织结构变化过程,并对其进行显微硬度测定的比较。试验结果表明,镍基合金热喷焊层经激光重熔处理后,组织得到明显的细化和改善,重熔喷焊层组织主要由细小的树枝晶及枝晶间极细的层片状共晶构成;在时效温度(600℃)一定的条件下,随着时效时间的延长,树枝晶仍保持原来的形态,而共晶组织发生球状化过程改变了层片状组织形态,同时基体中析出了大量弥散分布的硬质相,使重熔喷焊层仍保持较高的硬度;在时效时间(6 h)一定的条件下,随着时效温度的不断升高,树枝晶也发生明显的变化,转变为等轴状,同时基体中析出的碳化物相不但发生聚集长大,而且类型也发生转变,使重熔喷焊层的硬度开始逐渐下降;当时效温度超过800℃后,重熔喷焊层的硬度出现较大幅度下降的趋势。

Microstructure changes of laser remelted Ni-based alloy hot sprayed-welding layers after different aging treatment are studied by means of optical microscope（OM）,scanning electron microscopy（SEM） and X-ray diffraction（XRD）,and microhardness is also compared.The results show that,after laser remelting,microstructure of hot sprayed-welding layers has been significantly refined and improved,the remelted layers mainly consist of fine dendrites with small lamellar eutectic structure in their branches.When aging temperature is kept constant（600 ℃）,with the extention of aging time,the morphology of dendrites remain original,but the eutectic structures nodulize and lose their lamellar structure.And at the same time,a lot of hard phase precipitate in the matrix,which enable matrix a high hardness;When aging time is kept constant（6 h）,with the increasing of aging temperature,the morphology of dendrites become equiaxial apparently,meanwhile,precipitated carbide grow up together and its type has also changed,which led to a decline of layer hardness;When aging temperature exceed 800 ℃,the hardness of remelted layer fall sharply.