| The brazing diamond technology is featured for advantages of strong bonding strength,high grit protrusion height and large inter-grit chip space.It completely avoids the defects of traditional electroplated and sintered diamond tools.It has been considered as a revolutionary breakthrough in the field of superhard abrasive technology tool.In this paper,a Fe-based alloy powder is used as the filler alloy to brazing diamond by laser heating,and the interfacial bonding mechanism and the performance evaluation are investigated and addressed.The main work contents:setting up the laser brazing diamond preheating platform;investigating the technological parameters of laser brazing diamond with Fe-based filler metal under preheating conditions;analyzing the microstructure and interfacial products of brazing diamond/brazing layer/matrix interface;evaluating the shear strength of the laser brazed diamond by a single grit shearing test;and assessing the grinding performance by grinding granite.The main conclusions of this paper are summarized as follows:1.The laser heating parameters for brazing diamond with Fe-based filler metal are recommended as:laser power is 140 w,scanning speed is 0.30 mm/s,negative defocus amount 13 mm.The diamond surface has complete crystalline form,no obvious thermal damage and uniform and dense weld bead.2.Interface micro-aspect:the enrichment of Cr element in brazing alloy towards diamond interface.At the same time,Fe and Cr elements react with diamond to form M7C3 eutectic carbide on the surface of diamond.A"white bright band"is formed at the interface between the filler alloy and the steel substrate,which strengthens the effective connection between the filler alloy and the steel substrate.3.The influence of laser scanning speed on residual stress of brazed diamond is analyzed.The trend of Raman wave number of diamond at three different scanning speeds increases first and then decreases.After brazing,a small tensile stress is detected at the top of diamond,and then transforms into compressive stress.The maximum residual stress occurs in the middle and lower parts of diamond.4.The diamond shear stress test shows that the main failure mode of diamond is fracture,and the bonding strength between brazing filler metal and diamond is much greater than that of diamond itself.The shear force increases first and then decreases with the increase of laser power,and decreases with the increase of scanning speed and negative defocusing.5.The test of diamond abrasive grinding performance shows that the main form of diamond abrasive breakage in laser brazing with Fe-based filler metal is micro-breakage,and only a small amount of diamond in the grinding process is in the form of shedding failure. |
