The electric spark deposition method was used to strengthen TC4 alloy surfaces under powdermixed near-dry EDM.Through the medium mixed with B4 C powder

graphite electrode as the tool electrode

the hardness of titanium alloy surface was improved by forming strengthening layer with enriched in C

B

Ti and Al phases.The results indicate that dense

well combined with matrix and cascade chrysanthemum petal-like microstructure can be observed

and with increasing in current

the grain size is increased.It is found that the micro-hardness of about 899 HV and 1 039 HV can be obtained when the current is 3.7Aand 6.6A

which is improved significantly compared with that of the original alloy（about 312HV）.XRD results reveal that TiC

TiB

B

8

C

Al

3

BC

Al

3

Ti and Al

5

Ti

2

phases can be observed in the strengthening layer.The metastable phase of Al

3.3

Ti appears

and the phase of Ti-Al intermetallic compound is increased significantly with the current of 6.6A.