Study On Preparation And Wear Of Brazed Diamond Thin-wall Drill

The silicon nitride engineering ceramic ball valve is widely used in many industrial field with its high abrasive resistance, high hardness and corrosion resistance, such as chemical, metallurgical, sewage treatment and so on. Because of the high hardness and brittleness, it is very hard to drill on the silicon nitride engineering ceramic. At present, the first priority of drilling on the silicon nitride ceramic is to use brazed diamond thin-wall drill. Based on the experiment of drilling on the silicon nitride engineering ceramic, the preparation and wear of brazed diamond thin-wall drill have been studied.Firstly, based on the analysis of the machinability of the silicon nitride engineering ceramic, the principle to choose diamond, solder and base have been studied, the brazing form has been confirmed and the preparation process have been established. In addition, the preparation material of the brazed diamond thin-wall drill is as follows:SMD diamond of the size 45/50, Ni-based solder and base of #45 steel and the brazing form is vacuum brazing.Then, through the observation of the brazed diamond thin-wall drill after drilling on the silicon nitride with SEM and stereomicroscope, the wear form of the brazed diamond thin-wall drill was given and the wear mechanism and wear process have been studied. The result indicated that the wear of drill includes diamond grit wear and bond wear. Six kinds of diamond grit wear form are listed:spall, pitting, part fracture, whole fracture, dislodgement and wearing flat and two kinds of bond wear form are listed:part dislodgement and continuous dislodgement. At the beginning of drilling, the main wear form is diamond grit fracture, dislodgement and bond continuous dislodgement; in the transitional period, the main wear form is diamond grit wearing flat and bond part dislodgement; in the end, the tool has been invalid because of the large proportion of diamond grit wearing flat.At last, the influence of spindle speed, drilling force and wall thickness on the diamond grit wear with 10mm drilling depth have been studied. The result shows that the proportion of fracture and wearing flat increases with the increase of the spindle speed, but the dislodgement is almost unchanged; the proportion of fracture and dislodgement increases with the increase of the drilling force, but the wearing flat is almost unchanged; the proportion of all wear forms is almost unchanged with the increase of the wall thickness. It was founded that with the spindle speed of 710/mm, drilling force of 705N and wall thickness 1.5mm, the wear is not serious and the machining efficiency is high.