摘要：The present work describes an advance method of surface modification by electric discharge machining. In this work, additive mixed powder metallurgy copper tungsten electrode has been used for the surface modification of En-31 die steel. Three additives zinc stearate, calcium stearate and nickel were used in P/M composite electrode and their effect was analysed. The effect of compaction pressure, peak current, pulse on time and pulse off time on surface deposition rate, surface roughness and micro hardness of the deposited layer has been investigated. During pilot experimentation surface modification process was carried out with three different additives viz. zinc stearate, calcium stearate and nickel. The performance parameters predicted that calcium stearate is the best additive. Therefore further experimentation were carried out by using calcium stearate as additive in the manufacturing P/M electrode and its effect on surface modification of En-31 steel has been investigated. Central composite rotatable design (CCRD) technique was used for design of experiments and subsequent results have been analysed. Analysis of variance had been performed to check the adequacy of the developed mathematical models as well as significance of each term comprising the models. The maximum surface deposition rate achieved was 1.4mg/min at 7.5 Amps peak current, 20 µsec pulse on-time, 100 µsec pulse off-time and 700 MPa compaction pressure. The best value of surface finish obtained was 5.24 µm at 4.5 Amp peak current, 10 µsec pulse on-time, 200 µsec pulse off-time and 1100 MPa powder compaction pressure. The maximum value of micro hardness observed was 78.3 HRC at 7.5 Amps peak current, 10 µsec pulse on-time, 100 µsec pulse off-time and 700 MPa compaction pressure.
关键词：electric discharge machining; additive; response surface methodology; central composite rotatable design; analysis of variance
