摘要
目的增强42CrMo钢的耐磨性,改善其严重的磨损失效情况。方法采用激光熔覆技术同步送粉的方式在42CrMo钢表面制备金刚石/WC颗粒增强钴基复合熔覆层,借助SEM、EDS、XRD、显微硬度仪和多功能综合性能测试仪,研究了熔覆层宏观形貌与微观组织、物相组成、显微硬度与耐磨性。结果使用Ti/TiC粉末对金刚石进行预处理可以改善其烧蚀和石墨化;适量ZrH2提升了熔覆层宽厚比,促进了熔池对流传质作用,同时,活性元素Zr改善了金刚石颗粒的润湿性能,提高了黏结相对金刚石的把持力。熔覆层多道搭接过渡均匀,其显微组织主要由细小枝晶及致密网状碳化物共晶组成,熔覆层与基体结合区域反应生成了平面晶组织,进而提高了熔覆层结合强度。激光熔覆热特性使W2C、ZrC、γ-(Co,Fe)、M6W6C、CoZr_(2)、(Ti,Zr)O_(2)、TiCx、Co_(3)Ti等物相存在于熔覆层内,细晶强化及弥散强化作用使得熔覆层的平均显微硬度(1002HV0.2)是基体的3倍。熔覆层平均磨损量是基体平均磨损量的1/2,熔覆层平均摩擦因数也明显低于基体,表明熔覆层的耐磨性能得到提升,其磨损机制主要为磨粒磨损,熔覆层内金刚石因承担摩擦载荷而钝化,但磨痕中的金刚石完整且未发生脱落。结论金刚石/WC颗粒增强钴基复合熔覆层的耐磨性显著提高,可用于42CrMo钢表面强化。
The work aims to enhance the wear resistance of 42CrMo steel and improve the serious wear failure of 42CrMo steel.The cladding layer with material of diamond/WC particles reinforced Co-based composites was produced on the 42CrMo steel surface by a laser synchronous powder feeding machine.The laser power was 700 W during the cladding process,the powder feeding rate was 21 g/min,the scanning speed of the spot was 180 mm/min,the carrier gas flow rate was 4 L/min,the distance between the substrate and the laser cladding head was 13 mm,and the overlap rate between the adjacent cladding passes was 30%.The polished cross section was corroded with 10%HNO3 alcohol solution to prepare metallographic samples.Macro morphology and microstructure of the cladding layer were observed by SEM and EDS.The phase composition was detected by XRD,the microhardness of the cladding layer was measured by microhardness tester and the friction and wear tests were carried out.The diamond particles pretreated by Ti/TiC powder could improve graphitization and ablation.An appropriate amount of ZrH2 powder could improve the ratio of the width of the cladding layer to its thickness,and promote the convection mass transfer in the molten pool.At the same time,the active element Zr could improve the wettability of diamond and the metal bond could hold the diamond particles strongly.The overlapping cladding layer performed a regular surface and the microstructure of the cladding layer was mainly composed of fine dendrites and dense network carbide eutectic.Rapid melting and freezing velocity at the bonding interface could make all elements diffuse and change in gradient,and generate planar crystals with appropriate dislocation and slip ability.Therefore,the bonding strength between the cladding layer and the substrate was enhanced.The thermal characteristics of laser cladding was contributed to obtain the W2C,ZrC,M6W6C,γ-(Co,Fe),CoZr_(2),(Ti,Zr)O_(2),TiCx,Co_(3)Ti and other substances in the laser cladding,and the dispersion distribution of new carbide phase could significantly improve the microhardness of the cladding layer.The average microhardness(1002HV0.2)of the cladding layer was 3 times that of the substrate due to the fine grain and dispersion strengthening.The average wear mass loss with a value of 1.6 mg was obtained in sliding the cladding layer,which was the 1/2 compared with that in sliding the substrate.The average friction coefficient of the cladding layer was evidently lower than that of the substrate,indicating that the wear resistance of the cladding layer increased.The friction and wear test of the cladding layer showed that abrasive wear became the dominant wear mechanism in sliding the cladding layer,the diamond particles in the cladding layer were passivated,contributing to bearing the friction load.However,the diamond particles located in the wear track on the cladding layer kept an integrity statue and few grains were falling out.The microstructure of the cladding layer is uniform and dense,the microhardness and the wear resistance are significantly improved,so it can be used for surface strengthening of 42CrMo steel.
作者
罗亮斌
梁国星
刘东刚
郝新辉
黄永贵
赵建
LUO Liangbin;LIANG Guoxing;LIU Donggang;HAO Xinhui;HUANG Yonggui;ZHAO Jian(Shanxi Key Laboratory of Precision Machining,College of Mechanical and Vehicle Engineering,Taiyuan University of Technology,Taiyuan 030024,China;Provincial Technology Innovation Center of Advanced Precision Tool System,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2024年第5期96-107,共12页
Surface Technology
基金
中央引导地方科技发展资金项目(YDZJSX2021B003)
国家自然科学基金资助项目(52105473)
山西省基础研究计划项目(20210302124050,20210302124121)
山西省创新平台基地建设专项(202104010911007)
山西省高等学校科技创新项目(2021L086)。
关键词
激光熔覆
复合熔覆层
显微组织
显微硬度
耐磨性
laser cladding
composite cladding layer
microstructure
microhardness
wear resistance
