Kw Guo

By Kelvii Wei Guo

Part of the book: Welding Processes

By Kelvii Wei Guo and Hon Yuen Tam

Due to the trend of miniaturization, the specific advantages of metal forming, especially for the high productivity and material utilization, cannot be exploited to the same extent in the field of electronics production as in conventional metal forming. Because of the competition with less productive and environmentally more polluting technologies, micropunching is extremely suitable for mass production of micro features, and the quality of the relevant punched microholes is definitely attracted to its successful application. Herein, the effect of cobalt on the morphology of microhole formed by punching with tungsten carbide-cobalt (WC/Co) micropunches was investigated. The results reveal that due to the optimal joint-contribution of WC and Co, the morphologies of microholes punched by 75% vol. WC+ 25% vol. Co micropunches not only satisfy with the practical requirements but also the punch using life is at the highest level among the three types of micropunches. Moreover, for 75WC/25Co micropunch, the serious wear of micropunch occurs with the wear loss of Co and WC when the punching number exceeds 1525. With the further increase in punching numbers, the dominant factors of the wear loss would mainly rely on the easily peeled off WC due to the serious loss of Co.

Part of the book: Cobalt

By Kelvii Wei Guo and Hon Yuen Tam

The use of microholes is a potential approach to enhance fluid flow and heat exchange within thermal power plants, especially for the turbines. Ascribed to eco environmental competition, micropunching is extremely suitable for the mass production of micro features with friendly eco effects. Therefore, the morphology variation of micropunch and microhole during the punching with WC/Co micropunches was investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and confocal laser. Results reveal that due to the optimal joint contribution of WC and Co, the formed microholes satisfy with the practical requirements in the quasi stable period. Moreover, the serious wear of micropunch occurs with the wear loss both of Co and WC when the punching number exceeds 1525. With the further increment in punching numbers, the dominant factors of the wear loss would mainly rely on the easily peeled off WC due to the serious loss of Co. In addition, the microholes can be adequately processed after about 30 min by natural sand grains. The quality of the hole would decrease with further increase in processing time and sand accumulation becomes severe.

Part of the book: Thermal Power Plants