金刚石线锯钎焊机理及工作层疲劳裂纹特征分析

Brazing mechanism and surface crack characteristics of diamond wire saw

在氩气气氛条件下利用Cu-Sn-Ti预合金钎料实现人造金刚石磨料与KSC82钢丝的钎焊连接,制作长度500 m,基体直径约为0.7 mm的金刚石线锯。利用扫描电子显微镜及能谱仪观察并分析金刚石钎焊界面特征及微区元素分布规律,探讨钎料及钎焊界面元素氧化特性,开展线锯弯曲疲劳实验。结果表明:Cu-Sn-Ti合金在钎焊后内部形成成分发生偏析的组织,金刚石磨粒钎焊界面Ti元素明显偏析,金刚石通过反应型润湿方式实现钎焊连接。氩气通入流量影响线锯工作层合金表面显色,当氩气流量Q≥15 L/min时,线锯工作层表面呈金黄色;当10L/min≤Q≤15 L/min时,呈蓝色;当5 L/min≤Q≤10 L/min时,呈紫红色,工作层合金表面Ti元素的氧化层厚度决定其表面可见颜色类型。线锯工作层表面弯曲疲劳裂纹首先发生于无钎料合金包覆的基体表面,增大弯曲曲率,金刚石钎焊界面处裂纹发生并沿着垂直于钎焊界面方向向钎料合金扩展,具有典型的张开型表面裂纹特征。

Diamond grits were brazed on the surface of the KSC82 steel wire by using Cu-Sn-Ti pre-alloy powder, diamond wire saw was produced with steel wire of diameter 0.7 mm and length 500 m. Diamond brazing interface features and elements distribution pattern were analyzed by using the scanning electron microscopy and energy disperse spectroscopy. Elements oxidation properties of diamond brazed interface were discussed, and fatigue bending test was carried out. The results show that the segregation of the alloying elements happens inside the Cu-Sn-Ti alloy after brazing heating treatment, Ti element segregates on the diamond brazed interface and its content increases 18 times. The diamond grains are brazed because of the titanium carbide. Titanium oxide phenomenon is found on the surface of Cu-Sn-Ti alloy, and only being found on Cu-Sn-Ti surface. Titanium oxide thickness depends on the argon flow Q during argon controlled atmosphere-brazing, when Q≥15 L/min, alloy surface shows gold color; when 10 L/min≤Q≤15 L/min, blue shows on the alloy surface; when 5 L/min≤Q≤10 L/min, alloy shows amaranth color. Bending fatigue crack occurs on the surface of KSC82 steel wire firstly, and cracks occurs in diamond brazing interface and growth along the circumferential of the wire saw to Cu-Sn-Ti alloy with the characteristics of opening mode crack when bending curvature increases.