The electric spark deposition method was used to strengthen TC4 alloy surfaces (with or without carbide
layer coating, respectively) under kerosene-based oil or misted deionized water medium conditions. The microstructure,
phase compositions and microhardness of strengthened layer were investigated. The results indicated that
microstructure of strengthened layer showed chrysanthemum petal-like. Under kerosene-based oil medium condition,
compared with uncoated surfaces the quantity of carbide after coating on alloy surface was increased,which were overlapping
on edges of petals as while. Under misted deionized water medium condition, the distribution of carbides on
strengthened layer was more disperse and uniform. Analysis for phase composition of strengthened layer showed that it
was composed of α-Ti and TiC. In addition, compared with primary TC4 alloy, the microhardness of strengthened
layer was improved significantly. The microhardness was measured to be about 800 MPa under both medium condition
while it showed more stable performance in misted deionized water medium condition.