The Basic Requirements of High Temperature Resistance Coating Material

1. The material have enough high-melting point. The higher the melting point of coating material is, the higher temperature it can be used.

2. Good chemical stability in high temperature is needed, including not having harmful high temperature chemical reaction with environmental medium. The material itself won’t decompose or sublimate into harmful crystalline form in high temperature.

3. Requirement of thermal fatigue property. In the thermal fatigue condition of cool & hot alternation. The base material and coating material should have reasonable match with coefficient of thermal expansion, thermal conductivity or other thermophysical properties. If there is a big difference, operator should use Hierarchical coating for transition, otherwise it will cause peeling off of coating.
In the progress of the thermal cycle at high temperature, the inside of base material or coating material will have phase transformation. It will cause volume stress, and coating layer will crack or peel off because of change of volume. For example, ZrO2 crystal, the monoclinic system will change to cubic system in 1010℃, and it will appear 7% change of volume. So when used for high temperature resistant ZrO2 coating layer, all of them should take measure of stabilizing treatment.

4. High temperature resistant oxidation alloy, it should contains alloy element with high appetency with oxygen. Normal element is Cr Al Si Ti and Y, etc. They have high appetency with oxygen. Their oxide is very compact with stable chemical property, and the volume of oxide is bigger than metal atom, so it can clad base metal effectively to avoid further oxidation.

5. The microscopic structure requirement of high temperature alloy. Normally metal parent phase with face centered cubic lattice is suitable for high temperature alloy, and it can be solution strengthening by atom of high melting point refractory metal. Or chemical reaction will occur between alloy element. It will form common lattice structure y’ phase with parent phase, and it will occur invigorating effect with parent phase. Or it can form high melting point compound between metal. The effect of compound is grain boundary strengthening and dispersion strengthening to parent metal.

WISDOM common high temperature resistant coating material
FeCrAl, Ni80Cr20, Inconel 625, NiCrTi