**2.1 Flame spray coatings**

Oxy-hydrogen and oxy-acetylene systems are preferred in flame spray coatings and usually refractory oxides which have lower melting point than 2760 0C are used in coating with these systems. Before ceramic coatings, a binding layer resistant to high temperature like nickel-chromium should be applied to material surface for preventing oxidation as can be seen in Fig. 3. Otherwise, ceramic coating can't adhere to the surface properly. Coating speed in flame spray method is relatively slow and it changes between 4.4x10-5 and 1.13x10-3 m/s. There are two flame spray method which are wire flame spray method and powder flame spray method (Geçkinli, 1992).

Fig. 3. Ceramic coated material surface, binding layer and coating layer
