Coating Configuration Requirements

In order to achieve the above goals, the major parameters that have to be considered are:

1. Coating/substrate adherence.

2. Low residual stress in the coating and coating/ substrate interface.

3. Excellent oxidation resistance and low permeability of oxygen through the coating configuration.

4. Improved mechanical strength and tow coefficient of friction at room and elevated temperature and high thermal shock resistance.

5. Minimum chemical interaction between the substrate and the coating and coating stability at working temperatures.

Since a single monolithic type coating would not be capable of satisfying all the above requirements, a multilayered coating system is proposed (see Fig. 1). The coating configuration is divided into two layers: an intermediate layer and an outer protective layer. These are continuously deposited to give a graded coating without any sharp compositional interfaces.

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