Titanium alloys is of interest for various desirable properties such as corrosion resistance, bio compatibility and high specific strength. However,their tribological properties is generally poor relative to that of steel. Contents of this book includes introduction on various surface treatment of titanium alloy such as thermochemical treatment and hard coating. Recent concept of duplex coating is also described. The main focus of this book is on the surface treatment of titanium alloy via DC triode plasma nitriding; its principles of operation and basic mechanisms. This is contributing towards substrate enhancement for duplex coating system.