The effects of the plasma gas composition (Ar-N2, Ar-H2), arc current and voltage on the temperature and velocity of a low power (5 kW) plasma torch in the arc field free region have been investigated using an enthalpy probe. Coatings of Al2O3-13TiO2 were deposited under different conditions. The results show that in the Ar-N2 plasma, the enthalpy, temperature and velocity change little with arc current and voltage when regulating the nitrogen proportion in the plasma gas, and the hardness of the resulting coatings is 800-900 HV. For Ar-H2 plasma, however, increasing the H2 content in the gas mixture remarkably enhanced the velocity and heat transfer of the plasma jet with the result that the coatings showed the high hardness up to 1200 HV.

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