Y_2O_3含量对38CrMoAl钢表面激光合金化WC/Ni金属陶瓷组织与性能的影响

Influence of Y_2O_3 Content on Microstructure and Properties of Laser Alloying WC/Ni Metal Ceramic on 38CrMoAl Steel

采用激光合金化技术,在38CrMoAl钢表面制备不同Y_2O_3含量的WC/Ni合金化层。利用X射线衍射仪(XRD)、扫描电镜(SEM)、电子探针(EPMA)、显微硬度计和摩擦磨损试验机,系统研究合金化层的相组成、显微组织、显微硬度及摩擦磨损性能随Y_2O_3含量的变化规律。结果表明:不同Y_2O_3含量的合金化层皆是由γ-(Fe,Ni)、基体马氏体、M3C及WC相组成,其中纳米WC颗粒主要分布在合金化层上部的枝晶间,而微米WC颗粒则分布于合金化层底部边缘区,且在颗粒边缘形成有明显的外延生长层。随着Y_2O_3含量的增加,具有亚共晶形貌特征的凝固组织逐渐细化,γ-(Fe,Ni)和M3C数量增多,基体马氏体数量略有减少。但当Y_2O_3含量(质量分数,下同)超过1.0%时,凝固组织开始有所粗化。随Y_2O_3含量增加,合金化层硬度呈先增后降、摩擦因数和磨损失重呈先减后增的变化趋势。当Y_2O_3含量为1.0%时,合金化层硬度(781HV0.2)最高,为基体的2.4倍;摩擦因数和磨损失重最小,分别为基体的17%和8.9%。

WC/Ni reinforced layers with different Y2O3 contents were fabricated on the surface of 38 CrMoAl steel by laser alloying.The influence of Y2O3 content on the phase composition,microstructure,microhardness and tribological performance of the alloying layers were investigated via X-ray diffraction,scanning electron microscopy,electron microprobe,Vickers hardness tester and friction wear testing machine.The results show that the alloying layers with different Y2O3 contents all consist ofγ-（Fe,Ni）,martensite matrix,M3C,and WC phases.Nano-WC particles are mainly distributed between the dendrites in the top of the alloying layers,while the micro-scale WC particles with epitaxial growth layers are observed in the bottom of alloying layers.With the increase of Y2O3 content,the solidified microstructure with hypoeutectic morphology gradually refines,the number of theγ-（Fe,Ni）and M3C increases,and the number of martensite matrix decreases slightly.When Y2O3content（mass fraction,the same below）is more than 1.0%,the solidified microstructure slightly coarsens.With the increase of Y2O3 content,the hardness of the alloying layers increases first and then decreases;the friction coefficient and the wear mass loss exhibit the opposite trend.When the Y2O3 content is 1.0%,the hardness of the alloying layer is the highest,which is2.4times of hardness of matrix;the friction coefficient and the wear mass loss are the lowest,which are 17% and 8.9% of the matrix respectively.