Study On Improving Performance Of Electroplated Diamond Bit With Rare Earth

There have been great improvements in the manufacture of diamond tool in past several decades. Its applied range has been expanded continuously and extensive applications to geological exploration, petroleum extraction, machining of building materials, processing of gem, medical care and manufacturing of plastic products obtained. Among the methods for manufacturing of diamond tools, electroplating method has unique merits and is one of the most promising direction in the research of manufacturing diamond tools disusing of high temperature. As an important kind of electroplated diamond tool, electroplated diamond bit has been developed for thirty years and its manufacturing technique has been highly improved. However, some problems still exist, such as long production cycle, quality instability, narrow applied range. So it is impending and significant to realize high-speed production of electroplated diamond bit to increase production rate and quality in order to meet the expanding market demand. The main content of electroplated diamond bit research is research of electroplating matrix material. Electroplated diamond bit usually adopts nickel or nickel alloy as matrix material. Although nickel electroplating has been studied extensively in surface engineering, in electroplated diamond bit research more directing researches are needed owing to the different requirements of performances of plating bath and deposit between in diamond bit electroplating and in surface engineering. Rare earth material is a hot direction in material science due to the unique 4f electronic shell structure of rare earth elements, which results in the special properties of rare earth metal and rare earth alloy. In electroplating, rare earth has been industrially applied to chromium electroplating and tin electroplating. But there are few applied reports on rare earth in nickel electroplating so far and no report on effect of rare earth on mechanical property of deposit and performance of electroplated diamond tool is found. Drawing lessons from successful application of rare earth to electroplating, this paper is to introduce rare earth into the manufacture of electroplated diamond bit to obtain optimum electroplating technique of electroplated diamond bit through experiments and theoretical analysis, realizing the high speed and high quality production of electroplated diamond bit. Through analysis, concentration of rare earth, concentration of cobalt sulfate, bath temperature, cathodic current density and bath pH were chosen as elements affecting the performance of deposit and plating bath. For every element, four levels were studied. Experiments were scheduled by orthogonal design method.In electroplating, the performance of deposit is dependent on bath composition and electroplating operational parameters. As matrix material of diamond bit, deposit should have some performances same as those required in surface engineering, at the same time other special performances are required. So different bath performances are required. Bath for electroplating diamond bit needs good throwing power, but its covering power can be a little lower. Amongbath performances, throwing power, covering power and current efficiency were considered in this paper. Throwing power was measured by far-cathode near-cathode method. In experimental scope, bath throwing power increases with the increasing concentration of rare earth. The throwing power of conventional nickel bath was -7.7%. Compared to that of conventional nickel bath, the throwing power of bath with rare earth had been enhanced obviously. So addition of rare earth can overcome the shortcoming of bad throwing power of conventional bath. Bath temperature also had clear effect on throwing power. With the increase of bath temperature, the throwing power increases little by little. This may be related to the increase of bath conductivity resulting from high temperature. Bath covering power was measured by inner hole method. With the presence of rare earth, bath's covering power decreased...