Surface of TC4 alloy was treated in kerosene-based oil

misted deionized water and near-dry powder-mixed medium conditions with the graphite electrode by electric sparking deposition. The microstructure

phase constituent and micro-hardness of the strengthened layers were investigated by SEM （scanning electron microscope）

EDS （energy dispersed spectrometer） and micro-hardness testing. The results indicate that microstructure of strengthened layer prepared in the three medium exhibits chrysanthemum petal-like. The strengthening layer morphology is similar in misted deionized water and in near-dry powder-mixed medium conditions

which is more compact than that in kerosene-based oil condition. Phase constituent of strengthened layer on the TC4 alloy prepared in the three medium was analyzed. The results show that the strengthened layer is composed of α-Ti and TiC in kerosene-based oil and misted deionized water medium

while it contains TiB in near-dry powder-mixed medium condition besides α-Ti and TiC phase. In addition

compared with that of the TC4 alloy matrix

the micro-hardness of strengthened layer prepared in the three medium is improved significantly

in which the maximum performance is achieved from original average micro-hardness 300 HV to 1 200 HV in near-dry powder-mixed medium.