**1. Introduction**

98 Ceramic Coatings – Applications in Engineering

Wu, Z.Y.; Hill, R.G.; Yue, S.; Nightingale, D.; Lee, P.D. & Jones, J.R. (2011). Melt-derived

*Biomaterialia*, Vol.7, No.4, (April 2011), pp. 1807–1816, ISSN 1742-7061 Xue, W.; Liu, X.; Zheng, X. & Ding, C. (2005). In vivo evaluation of plasma-sprayed

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bioactive glass scaffolds produced by a gel-cast foaming technique. *Acta* 

wollastonite coating. *Biomaterials*, Vol.26, No.17, (June 2005), pp. 3455-3460, ISSN

In plasma arc spraying process also known as plasma spraying process, the thermal energy of an electric arc (40 kW or 80kW) together with a plasma forming gas, which would be either nitrogen or argon, are utilized in melting and propelling of the deposit material at high velocities (600 mS-1) onto a substrate. This process is capable of generating very high temperature, exceeding 16,000 C, which can be gainfully employed in the deposition of materials with high melting points. The deposited material is generally in a powder form and requires a carrier gas to feed it into the combustion chamber. The process enables discharging high bond strengths of the coatings due to the very high propulsion velocities of the impinging particles.

In a DC plasma arc process, gas heating is enough to generate core plasma temperatures exceeding 20000 °C depending upon the properties of gas and its electrical break down characteristics. Enthalpy of the gas is an indicator of its heating potential while it is getting translated to plasma state.
