【作者】 陈珍珍；

【导师】 徐九华；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2009， 硕士

【摘要】 单层钎焊立方氮化硼(CBN)砂轮凭借高温钎焊时在磨粒、钎料层、及砂轮基体之间界面反应形成的化学和冶金结合,实现了钎料层对CBN磨粒的牢固把持,具有磨料出露高度大、砂轮锋利、容屑空间充裕等显著优势。目前单层钎焊CBN砂轮的研制已取得一定的进展,但CBN磨粒钎焊过程中仍存在一些问题亟待解决,如:Ag-Cu-Ti钎料的剧烈流淌导致钎料层厚度不均,焊后CBN磨粒棱角被钎料层包覆难以出露,以及钎焊时CBN磨粒与钎料之间的界面反应难以主动调控致使磨粒棱角损耗过度、磨粒强度下降等。这些问题阻碍了钎焊CBN砂轮加工性能的进一步提高。为解决上述问题,本文采用在Ag-Cu-Ti合金钎料中添加TiN增强颗粒组成的复合钎料,开展CBN磨粒的钎焊试验研究。本文完成的主要研究工作包括:(1)采用三维视频显微镜、扫描电镜等仪器分析了TiN增强颗粒对Ag-Cu-Ti钎料铺展性和显微组织的影响,利用电子万能试验机测试了复合钎料钎焊接头剪切强度。结果显示,添加了TiN颗粒后的Ag-Cu-Ti合金钎料在45钢基体表面的铺展性可得到有效控制,钎料层的显微组织得到细化,钎料层的显微硬度和钎焊接头的剪切强度得到明显提高。(2)对TiN颗粒增强Ag-Cu-Ti复合钎料层与CBN磨粒之间的界面反应及新生化合物的微观特征进行了研究,并测试了钎焊CBN磨粒的静压强度。与Ag-Cu-Ti合金钎焊CBN磨粒的界面反应物相比,TiN颗粒抑制了界面反应,使得钎焊磨粒界面反应产物的总量显著减少。TiN含量在0~12 wt.%范围内,钎焊CBN磨粒的静压强度并无明显变化。(3)通过对复合钎料钎焊CBN磨粒形貌的观察发现,含4~8 wt.% TiN复合钎料钎焊的CBN磨粒包埋深度合适,钎料未铺展到CBN磨粒顶端,磨粒棱角得以出露,能保证足够的把持强度。选用Ag-Cu-Ti钎料和含4 wt.% TiN颗粒的复合钎料分别制作钎焊CBN磨头,并对其干磨削钛合金TC4的磨削性能进行了对比试验研究,验证了复合钎料可制作出性能更优的钎焊CBN磨头。更多还原

【Abstract】 Depending on the interfacial chemical and metallurgical reaction among the abrasive grains, the filler layer and the tool matrix, monolayer brazed CBN grinding wheels improve remarkably the joining strength to the grains and increase the space for holding chips. However, though much progress has been made on the development of brazed CBN wheels, some problems in brazing process are urgent to be solved. For example, the thickness of Ag-Cu-Ti filler layer is non-uniform because of the good flow of the alloy, the edges of the grains are wrapped by molten alloy and may be damaged during brazing. In addition, the interfacial reaction of the grains and filler could not be controlled positively. Therefore, this work carried out.the brazing experiments of CBN abrasive grains and 0.45%C steel using Ag-Cu-Ti alloy reinforced by TiN particles as composite filler. The main contents are summarized as follows:(1) The instruments, such as 3-D optical microscope and scanning electron microscope, were utilized to analyze the spreadability and the microstructure of the Ag-Cu-Ti composite filler containing TiN particles. The shear strength of the brazed joint was measured by electrical tensile equipment. The results show that, when the TiN particles added, the spreadability of Ag-Cu-Ti alloy on the 0.45%C steel matrix are controlled. At the same time, the microstructure of alloy layer is refined, the microhardness of filler layer and the shear strength of brazed joints are improved.(2) The TiN particles have prominent impacts on the shape and amount of the new-formed reaction products formed at the brazing interface of CBN grains and the filler layer. Otherwise, the compressive strength of CBN grains brazed using the composite filler is almost identical with that brazed using Ag-Cu-Ti alloy.(3) TiN particles control the wettability on the surface of the CBN grains. Compared with the CBN grains brazed using Ag-Cu-Ti filler, the top surface of the grains, which are brazed using the composite filler with 4 ~8 wt.% TiN particles, is not covered. Thus, the edges of the grains emerge. Two kinds of brazed CBN grinding-heads are fabricated using Ag-Cu-Ti filler and composite filler containing 4 wt.% TiN particles, respectively. The grinding experiments are carried out on titanium alloy TC4 without coolant. The results show that, the grinding-heads brazed using composite filler have better wear-resistance and higher machining efficiency than the ones using Ag-Cu-Ti filler.更多还原