摘要
硬质合金基微米晶金刚石涂层存在的晶粒粗大和结合性能不佳等情况,影响其在精密加工领域中的应用。为改善硬质合金基微米晶金刚石涂层的结合性能并细化金刚石晶粒,采用蒸发法在硬质合金表面沉积钨过渡层,经热处理后采用热丝化学气相沉积法在其上方沉积金刚石涂层,研究不同热处理温度对钨过渡层结构及金刚石涂层形貌、质量和性能的影响。结果表明:蒸镀的钨过渡层呈现非晶结构,随着热处理温度升高,钨过渡层的结晶度升高并形成不同尺寸的“孤岛−沟壑”结构。SEM图像、X射线衍射图谱和拉曼光谱显示,经热处理后钨过渡层上生长的金刚石涂层晶粒尺寸变小,结晶度更高。900℃热处理30 min的钨过渡层表面“孤岛−沟壑”结构尺寸适中,均匀性最好,其上生长的金刚石涂层平均晶粒尺寸约为1.97μm,平均摩擦系数最低;对应的摩擦副表面最平整,磨损率也明显降低。900和1000℃热处理钨过渡层上的金刚石涂层结合性能相比无过渡层样品有显著提高,在600 N载荷下分别达到HF2和HF1级别。
Objectives:Microcrystalline diamond coatings have extremely high hardness and excellent wear resistance,but their application field is limited by poor tribological and binding properties.To improve the tribological properties of microcrystalline diamond coatings on cemented carbide substrates,tungsten metal is chosen as the interlayer material,and microscopic texture is constructed by heat treatment on the surface of the tungsten interlayer.Methods:The evaporation method is used to deposit a tungsten interlayer on the surface of cemented carbide from which cobalt has been removed by an acid-base two-step method.The tungsten interlayer is then heat-treated in a reducing atmosphere with a certain proportion of argon and hydrogen gas mixture.After heat treatment for 30 minutes at various temperatures(700,800,900,1000℃ ),the effects of different heat treatment temperatures on the composition,morphology,and microstructure of the tungsten interlayer are studied using scanning electron microscopy(SEM)and X-ray diffraction(XRD).Diamond coatings are deposited using the hot filament chemical vapor deposition(HFCVD)method on substrates without any treatment and on tungsten interlayers heat-treated at different temperatures.The substrate temperature is controlled at(800±50)℃ ,and the growth time is 6 hours.The morphology and quality of the diamond coatings are analyzed using SEM,X-ray diffraction,and laser Raman spectroscopy.Reciprocating friction and wear tester are conducted using Si3N4 ceramic balls against the diamond coatings for 120 minutes to evaluate the friction performance of each coating sample.Results:The tungsten interlayer deposited by vapor deposition exhibits an amorphous structure,and its crystallinity significantly increases after heat treatment.Cracks are generated on the surface of the interlayer,forming"island-gully"structures of different sizes.The crystallinity of the tungsten interlayer after heat treatment at 700−800℃ is poor,with larger"island"and narrower“gullies”on the surface.The structure of the tungsten interlayer after heat treatment at 900℃ was more moderate,while the interlayer after heat treatment at 1000℃ has the best crystallinity and the smallest"islands".SEM surface morphology,XRD patterns,and Raman spectroscopy show that the diamond grown on the substrate surface without a tungsten interlayer has the largest average grain size and uneven grain size distribution.The crystallinity and content of diamond coatings grown on tungsten interlayers after heat treatment are better,as reflected in the higher diffraction intensity of the diamond peak in the XRD spectrum and the narrower full width at half maximum(FWHM)of the diamond peak in the Raman spectrum.The grain size of diamond shows a trend of first decreasing and then increasing with rising heat treatment temperature,but in all cases is smaller than that of the sample without a tungsten interlayer.Rockwell indentation tests are conducted on each diamond-coated sample under a load of 600 N,and the indentation morphology is analyzed using scanning electron microscopy.The indentation results indicates that tungsten interlayers heat-treated at 700 and 800℃ do not significantly improve the bonding properties of the diamond coating,with both exhibiting HF6-grade bonding strength.In contrast,heat treatment at 900 and 1000℃ effectively enhances the bonding properties of the diamond coating,with bonding strength grades reaching HF2 and HF1,respectively.The enhancement of bonding strength relies on the crystallinity of the tungsten interlayer and the formation of a good mechanical meshing effect due to the“island-gully”structure.Friction and wear results indicate that the diamond coating grown on the tungsten interlayer after 700℃ heat treatment has large drop.The coating grown on tungsten interlayers heat-treated at 800−1000℃ ensures good bonding performance while improving friction performance to varying degrees.Among them,the diamond coating grown on the tungsten interlayer heat-treated at 900℃ has the smoothest wear mark,with an average friction coefficient as low as 0.062,and the corresponding Si3N4 friction pair has the smallest wear mark diameter and wear rate.Conclusions:The tungsten interlayer and its“island-gully”structure after heat treatment can significantly improve the growth and crystal state of diamond,resulting in grain refinement and improved bonding and friction properties.The surface of the tungsten interlayer treated at 900℃ for 30 minutes produces a moderately sized“island-gully”structure and the best uniformity.The average grain size of the diamond coating grown on it is about 1.97μm,with the lowest average friction coefficient,and the corresponding friction pair wear rate is only 19.2%of the sample without a tungsten interlayer.The bonding properties of diamond coating on tungsten interlayer after 1000℃ heat-treated is significantly enhanced.
作者
王海龙
丁晟
马莉
魏秋平
WANG Hailong;DING Sheng;MA Li;WEI Qiuping(School of Materials Science and Engineering,Central South University,Changsha 410083,China;State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China)
出处
《金刚石与磨料磨具工程》
北大核心
2025年第4期448-457,共10页
Diamond & Abrasives Engineering
基金
国家“十四五”重点研究发展计划(2021YFB3701800)
国家自然科学基金(52202056,52274370,52071345,51874370)
广东省“十三五”重点研究开发项目(2020B01085001)
湖南省高新技术产业科技创新引领计划(2022GK4037,2022GK4047)
湖南省自然基金资助项目(2023JJ40722)
粉末冶金国家重点实验室自主课题(621022230)。
关键词
金刚石涂层
热处理
钨过渡层
晶粒尺寸
结合性能
摩擦磨损
diamond coating
heat treatment
tungsten interlayer
grain size
bonding properties
friction and wear
