Cemented carbide alloys (WC-Co, WC-TiC-Co) are electrolytically lapped in pretty high removal rate which is unproportional to electric current flowed. In relatively low voltage range (about 3 V, current density 5 A/cm
2) stock removal rate is 0.04g/A min and in high voltage range the rate gets down to 0.013g/A min so that a local maximum value is found out. In order to make clear this phenomenon, influences of working conditions on removal rates are investigated. High work pressure, high grinding ability of abrasives, high Co content of alloy make the local maximum rate higher. Surface roughness finished and lapping force, which is 250% of normal force, have also maximum value in the same range. Electronmicroscopic structures of alloy surfaces electrolytically lapped suggest the surface layer is weakend electrochemically.
Stock removal rate of electrolytic lapping is shown in the following equation.
W=
WE+
WM=
kI+
WM (
G, Q)
W : stock removal rate of electrolytic lapping
WE : electrolytic stock removal rate
WM : mechanical stock removal rate
I : electric current effectively flowed
k : coefficient given from Faraday's law and current efficiency
G : grinding ability factor of abrasives
Q : quality factor of carbide work
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