Titanium arc spraying was carried out in air atmosphere, and Air, N_2 and Ar gas were used as the atomizati-on gas. Crystalline structure and microstructure of surface and cross section in the coatings were stu- died. The following conclusions can be drawn from this work. Arc sprayed titanium coatings in air atmosphere are almost composed of TiN and TiN_(0.3), and their peaks height and gas contents in the coatings depend on the type of atomization gas. TiN_(0.3) is formed due to action of nitrogen as α-Ti stabilizer, then the TiN_(0.3) changes to the TiN with increase of nitrogen content in titanium. Difference of temperature in thermal spraying by heat of nitriding reaction have influence on microstructures. Binding strength of the interface between coating and substrate can be enhanced by formation of alloyed layer (β-Ti and/or Fe_2Ti) Rapid nitriding reaction is restrained up to 600mm in spraying distance by inert atomization gas, Ar. Nitrogen atomization is efficient in the TiN formation by arc spraying. The effect of oxygen on nitriding process is not recognized as any oxide. Ar atomization restrains in reacting titanium with the both nitrogen and oxygen, and promotes chemical bonding between coating and substrate.
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