功能电极钛合金表面TiN涂层的原位合成

In-Situ Synthesis of TiN Coating on Titanium Alloy Surface by EDM with Functional Electrode

针对功能电极电火花诱导烧蚀加工钛合金的表面缺陷,通过原加工系统向加工区域通入氮气,利用电火花放电对烧蚀加工表面进行修整,放电产生的热量促使氮气和钛合金表面材料发生化学反应,原位合成了TiN涂层,并利用扫描电子显微镜、X射线衍射仪、显微硬度计等检测手段对涂层进行测试.结果表明:加工过程中电火花放电稳定连续,能量利用率较高;涂层致密、均匀、连续,主要由TiN强化相组成,厚度可达400μm以上;TiN涂层显微硬度可达1761.8,是基体硬度的5.7倍;涂层与基体之间形成结合强度高的冶金结合且TiN相分布比较均匀;合成反应对电极有很强的反镀作用,电极端面以TiN强化相为主,能有效地降低电极损耗,同时避免了电极材料对涂层形成的污染,较好地保持涂层中TiN相的纯度.

Proposed in this paper is a new method to avoid the defects on titanium alloy surface formed during the EDM-induced ablation machining with functional electrode.In this method,nitrogen gas is injected into the pro-cessing area through the original processing system,and the electric spark discharge is adopted to trim the ma-chined surface.With the help of the heat due to the discharge,a reaction of nitrogen gas and titanium occurs,and the TiN coating is thus synthesized in situ.It is found from the SEM,XRD and microhardness test results of TiN coating that （1）the electric spark discharge process is stable and continuous in the process of coating formation and is of efficient energy utilization;（2）the coating is a dense,uniform and continuous layer dominated by TiN strengthening phase,with a thickness of more than 400μm;（3）the microhardness of the coating reaches 1761.8, which is 4.7 times more than that of the matrix;（4）there exists a metallurgical combination with high bonding strength and even TiN phase distribution between the coating and the matrix;and （5）the synthesis reaction has a strong reverse plating effect on the electrode,which causes a TiN strengthening phase-dominated electrode end face,effectively reduces the electrode spoilage,avoids the coating pollution caused by electrode elements,and effe-ctively maintains the purity of TiN phase in the coating.