激光熔覆VC-Cr_(7)C_(3)复合熔覆层的组织与力学性能  

Microstructure and mechanical properties of laser clad VC-Cr_(7)C_(3) composite layers

作　　者：王皓民 汪国庆[1] 熊杨凯 江昊 赵远涛 方志强 李文戈[2] Wang Haomin;Wang Guoqing;Xiong Yangkai;Jiang Hao;Zhao Yuantao;Fang Zhiqiang;Li Wenge(School of Materials Science and Engineering,Hainan University,Haikou Hainan 570228,China;School of Merchant Marine,Shanghai Maritime University,Shanghai 201306,China)

机构地区：[1]海南大学材料科学与工程学院,海南海口570228 [2]上海海事大学商船学院,上海201306

出　　处：《金属热处理》2022年第11期245-252,共8页Heat Treatment of Metals

基　　金：海南省自然科学基金(512115)。

摘　　要：采用激光熔覆技术在Q235钢表面原位合成了VC-Cr_(7)C_(3)复合熔覆层,并研究激光扫描速度对熔覆层微观组织与力学性能的影响。利用扫描电镜、X射线能谱仪和X射线衍射仪等对熔覆层组织及性能进行分析。结果表明,激光熔覆技术可使V、Cr、C混合颗粒间发生原位反应形成VC-Cr_(7)C_(3)复合熔覆层,其主要由黑灰色VC相、灰色Cr_(7)C_(3)相及{FeM}粘结相组成,其中Fe与Cr可共同形成Cr_(7)C_(3)相(M_(7)C_(3))。激光熔覆凝固形状控制因子K与C元素的分布状况使得熔覆层顶部出现大量碳化物等轴晶组织,中部碳化物等轴晶的含量有所减小,而底部由于C含量较低,其碳化物含量较少,且碳化物晶粒形貌受到激光扫描速度的影响,在1 mm/s时碳化物呈树枝晶组织,在1.5 mm/s时呈等轴晶组织。同时在1.5 mm/s时熔覆层晶粒尺寸明显小于1 mm/s时的。以上熔覆层组织结构与成分变化使其硬度随层深的增加而降低,同时随着扫描速度的增加,熔覆层的硬度也逐渐增加,熔覆层的硬度高于Q235钢3倍以上。在1.5 mm/s时熔覆层摩擦因数为0.4,低于Q235钢基材的0.6,且熔覆层磨损量显著低于Q235钢基材。由此可知,激光熔覆VC-Cr_(7)C_(3)复合熔覆层可用于碳钢的表面高硬、耐磨改性。Composite clad layer of VC-Cr_(7)C_(3) was in situ synthesized on the surface of Q235 steel using laser cladding technology,and the effect of laser scanning speed on microstructure and mechanical properties of the clad layer was studied.The microstructure and properties of the clad layer were analyzed by means of scanning electron microscope,X-ray energy dispersive spectrometer and X-ray diffractometer.The results show that laser cladding technology can cause in-situ reactions between mixed particles of V,Cr and C to form a composite clad layer of VC-Cr_(7)C_(3).It is mainly composed of black gray VC phase,gray Cr_(7)C_(3) phase and{FeM}bonding phase,in which Fe and Cr can form Cr_(7)C_(3) phase(M_(7)C_(3)).The laser cladding solidification shape control factor K and the distribution of C element result in a large amount of carbide equiaxed crystals at the top of the clad layer,with a reduced amount of carbide equiaxed crystals in the middle and less carbide at the bottom due to the low C content.The carbide shape is influenced by the laser scanning speed,with carbide dendrites appearing at 1 mm/s and carbide equiaxed crystals at 1.5 mm/s.At the same time,the grain size of the clad layer at 1.5 mm/s is significantly smaller than 1 mm/s.The above changes in the structure and composition of the clad layer cause its hardness to decrease as the layer depth increases.As the scanning speed increases,the hardness of the clad layer gradually increases,with the hardness of the clad layer being more than three times higher than that of the Q235 steel.The friction coefficient of the clad layer is 0.4 at 1.5 mm/s,which is lower than the 0.6 of the Q235 steel substrate.The significant lower wear loss of the clad layer compared to that of the Q235 steel substrate indicates that the composite clad layer of VC-Cr_(7)C_(3) can be used to modify the surface of the carbon steel for high hardness and wear resistance.

关 键 词：激光熔覆 原位合成 VC-Cr_(7)C_(3)复合熔覆层 显微硬度 耐磨性 

分 类 号：TG148[一般工业技术—材料科学与工程] TG113.25[金属学及工艺—金属材料]