【作者】 陈燕；

【导师】 徐鸿钧；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2009， 博士

【摘要】 高温钎焊单层金刚石工具具有磨粒出露高、容屑空间大、磨粒把持强度高等特点,因此具有高锋利度、高加工效率和磨料利用充分等性能优势,在难加工材料高效、重负荷加工中已显示出传统金刚石工具无法比拟的优异性能。但在其推广应用中发现现有的单层钎焊金刚石工具存在磨料非正常损耗的现象,包括在磨料顶部出现的过大的磨耗平台和较为频繁发生的微破碎、小块破碎和大块崩裂现象,偶尔在重负荷加工中还能观察到磨料原本出露的部分在钎料爬升高度的位置上被齐根切断,形成火山口状形貌。种种现象表明磨料在钎焊时已受到不同程度的热损伤。本文在分析国内外关于高温钎焊金刚石工具研究现状的基础上,围绕钎焊金刚石的热损伤形式、机理及控制等关键问题开展了深入的基础研究工作,并成功地研制了少无热损伤的钎焊单层金刚石工具,为开发新一代钎焊金刚石工具开辟了新途径。本文完成的具有创新意义的研究工作主要包括:(1)通过对现有工艺条件下,镍基钎料真空钎焊金刚石表面形貌的观察和分析以及焊后金刚石力学性能(静压强度、冲击强度与耐磨性)的测试,提出了钎焊高温、化学侵蚀及金刚石工作面上的残余拉应力是导致钎焊金刚石热损伤的主要因素。(2)开发了氩气保护条件下镍基钎料钎焊金刚石的新工艺方法。钎焊金刚石中没有出现微裂纹,耐磨性能下降较小。该工艺方法由于减小了镍基钎料的硬度,钎焊残余应力也随之减小。(3)采用自主研制的新型银基活性钎料真空钎焊金刚石试验进一步减小了钎焊金刚石的热损伤。钎焊金刚石表面没有出现石墨化与微裂纹;力学性能测试结果表明焊后金刚石基本上保持焊前的力学性能。(4)通过套料钻的对比加工试验表明,由于减小了钎焊金刚石的热损伤,镍基钎料氩气保护钎焊与银基活性钎料真空钎焊金刚石套料钻较镍基钎料真空钎焊金刚石套料钻具有更长的寿命,且钎焊金刚石磨损形式以正常磨耗为主。通过控制钎焊金刚石热损伤,研制的新一代钎焊金刚石工具可在确保对磨料的高结合把持强度的同时确保磨料在焊后仍可保持磨料原有强度、硬度和耐磨性。因此,课题研究成果的后续推广应用有望加快单层钎焊金刚石工具工业化生产的进程。更多还原

【Abstract】 With the features of high grain protrusion, large swarf clearance space and high bonding strength, brazed monolayer diamond tools have the advantages of high sharpness, machining efficiency and grains utilization ratio. Thus, brazed monolayer diamond tools are superior in high efficiency and heavy duty processing of difficult-to-cut materials to conventional diamond tools. But, there exit abnormal attrition of grains such as big wear flat, frequent micro-fracture and macro-fracture in the coarse of application. Occasionally, the grains are broken on the location of grain protrusion and the crater-shaped appearance is formed. These phenomena show that brazed diamond grains have suffered thermal damaged in brazing process.Based on the analysis of present research status of brazed monolayer diamond tools at home and abroad, the thermal damage forms, mechanism and control strategy of brazed diamond are studied. And the new-type brazed monolayer diamond tools with little thermal damage have been successfully developed.The main creative contents in this paper are summarized as follows:(1) The surface morphologies of the bazed diamond grits with Ni-based filler alloy by vacuum brazing are analyzed, and the as-brazed mechanical properties (such as static compressive strength, impact toughness and wear resistance) are tested. The results show that the key factors resulted thermal damage of brazed diamond are high brazing temperature, chemical erosion and brazing tensile residual stress.(2) The novel process of furnace brazing diamond under argon atmosphere has been developed. There is not any micro crack on the surface of diamond grits. Furthermore, the wear resistance of breazed diamond decreases slightly in comparison to the wear resistance of original diamond. Due to decreasing the strength of Ni-based filler alloy, the brazing residual stress in the brazed diamond is decreased.(3) The thermal damage of brazd diamond is further decreased by vacuum brazing with the self-developed new-type Ag-based filler alloy. There don’t exit micro cracks and graphite on the surface of brazed diamond. The test results of mechanical properties show that the brazed diamond has the same excellent mechanical property as original diamond.(4) By the comparison machining tests, the service life of brazed diamond core drills made by furnace brazing under argon atmosphere with Ni-based filler alloy and by vacuum brazing with new-type Ag-based filler alloy are longer than those made by vacuum brazing with Ni-based filler alloy. Furthermore, the attrition form of former brazed diamond core drills is a normal wear. Owe to the effective control of the thermal damage of brazed diamond, the new-type brazed monolayer diamond tools could not only have the high bond strength, but also have the same advantage in strength, hardness and wear resistance as original diamond. Thus, the application of research result in this paper can promote industrialization of brazed monolayer diamond tools.更多还原