钎焊金刚石膜的试验研究及机理分析

Experimental investigation and bonding mechanism of brazing diamond film

针对金刚石膜钎焊问题,采用粉末冶金法制备的Ag72-Cu28-Ti(1-5)钎料片,对金刚石膜与硬质合金进行了真空钎焊试验。在真空度<5×1012-2Pa,850℃×10min工艺条件下,实现了金刚石膜与硬质合金的钎焊连接。用扫描电镜、电子探针及X射线衍射区研究了金刚石膜与活性钎料界面,揭示了钎焊界面的形成机理。在钎焊温度下,液态Ag-Cu-Ti钎料合金中的活性成分β-Ti与金刚石膜表面的C具有较强的亲和力,通过吸附、扩散和化学反应,在金刚石膜表面出现了类金属TiC层,在以Ag-Cu共晶合金为基的钎料作用下,实现了金刚石膜与支撑体硬质合金钎焊连接。金刚石膜钎焊接头的四点弯曲强度测试表明,在文中的钎焊工艺参数下,钎料中Ti含量1％-3％时,其钎焊接头平均强度>300MPa。

Vacuum brazing of diamond and hard alloy were performed using Ag72-Cu28-Ti(1-5) filler alloy. The joint of diamond and hard alloy formed under conditions that pressure was less than 5 × 10-2 Pa, brazing temperature at 850°C and holding time of 10 min. The interface of the diamond film and the active filler metal was observed by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction to disclose the bonding interface mechanism. At the brazing temperature, there is greater affinity between active element (β-Ti) in the brazing filler metal and the carbon on the surface of the diamond film. A metal-like layer of TiC formed on the surface of diamond film due to adsorption, diffusion and chemical reaction. The layer and the Ag-Cu alloy based brazing filler metal bond the diamond film and the hard alloy together. Using the technical parameters, the four-point bending strength test shows that the average strength of the brazed joints is higher than 300 MPa when the active element is less than 3%.