Fundamental Research On Thermal Damage Of Brazed Diamond And Its Control Strategy

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.