Effect of Spraying Parameters on the Microstructure and Mechanical Properties of Micro-Plasma Sprayed Alumina-Titania Coatings

Electrical property of a micro-plasma spray system with different working-gas feedingschemes was tested to optimize the plasma spray process.The arc voltage with an integratedgas injection mode is higher than that with radial injection or axial injection modes.Thus,anintegrated gas injection mode with an excellent electrical characteristic was adopted to depositalumina-titania coating.The microstructure,bonding strength and hardness of the plasma sprayedalumina-titania coating,as a function of the spraying parameters,e.g.,plasma current,gas flowrate and gas pressure,were studied.It was shown that the spraying parameters affected remarkablyon the inicrostructure of the coating.Different tendencies in bonding strength and hardnesswere also shown for different spraying parameters.At an arc current of 250 A,a gas flow rate of20 L/rnin and a gas pressure of 0.5 MPa,the bonding strength and micro-hardness of the coatingsreach 40.6 MPa and HV1406.1,respectively.