Bi-directional Pulse Composite Electroforming Technology Experimental Study

Composite electroforming technology is a manufacturing method which composite particles is added to electroforming solution in order to make it and metal ions codeposition. The composite electroforming layer exhibits higher microhardness , and is greatly enhanced in wear resistance,corrosion resistance and high-temperature oxidation resistance. At present , the research on composite electroforming is still in exploratory stage,codeposition theory on composite particles and metal irons is not perfect. The study on such as the preparation of nanocomposite coatings technology , the evenly dispersed issue of nanoparticles in the bath and coatings,and the role of mechanisms of composite particles in coatings in weak relatively. This restricts seriously further study and application on composite electroforming technology.First of all, in this paper, the mechanism of pulse current electroforming is introduced. Pulse current parameters affecting on electroforming process have been analyzed. The mechanism and models of composite electroforming is discussed and the influencing parameters, such as current density of the cathode, the suspended amount of composite particle, PH value and temperature are analyzed. Several composite particles, including in nano Al2O3, nano ZrO2 and nano TiN are selected during electroforming experiment. Nano composite particles can be suspended by ultrasonic agitation system. Experiments on bipolar pulse composite electroforming process are done. The microstructure and microhardness of electroforming is detected or tested. Also composite electroforming moulds are gained by experiments. Finally, conclusions were as follows:1. Bipolar pulse current could refine grain, reduce internal stress and result in better precision and surface finish, thus promote physical and mechanical properties of electroforming Products.2. The suspended amount of nano TiN composite particle, ultrasonic power and pulse current density is several main parameters, which influence on the property of composite electroforming layer and the proportion of composite particle. The proportion of nano TiN composite particle in composite electroforming layer is increased, electroforming layer is more flat and microstructure is more compact. Pulse current density increases, the nano TiN composite particle content reduce in composite electroforming layer, also crystallization more bulky. The testing results showed that microhardness can be improved 80% and reach 530HV, Compared with nickel electroforming. The proportion of nano TiN achieves 4.83 wt % during ultrasonic compound electroforming.3. The main parameters on composite electroforming process have solution temperature, Electric current density, pH value and pulse parameter such as current wave form, etc. By optimizing these process parameters, it concludes as follows:Temperature is best to be controlled between 45℃and 50℃, PH value is between 3.5 and 4.5, ultrasonic power is two hundred watt, pulse positive current density is appropriate to control about 5 A/dm2 and pulse negative current density is applying 0.5 A/dm2. Pulse duty cycle is appropriate to control about 20%, TiN composite particle concentration is 12g/l, active agent concentration is about 120mg/l.