Sure, it is possible to influence the integrity of the bond coat during heat treatment. One must consider the specific heat treatment parameters as well as the coating-substrate interdiffuison behavior.
Dear Kajaı, Dr. Kammerer is perfectly right for her remarks. Since the ceramic suppresses oxidation, in some applications it is even possible to use materials with relatively poor oxidation resistance as bondcoats, and providing bondcoat temperatures remain below 950°C, simple Ni-Cr alloys can be used successfully.The resultant coating is rapidly oxidized above this temperature, and isothermal soaking under a typical thermal barrier ceramic for as little as 150 h at 1050°C can cause complete conversion of the bondcoat from metal to oxide.As this occurs in a stress-free condition, the ceramic remains adherent until the system is allowed to cool. High expansion mismatch stresses, and poor mechanical integrity in the oxidized bondcoat then combine to cause dramatic ceramic exfoliation. BEST REGARD
Note: Admixing free aluminium to these alloys produces an exothermic reaction on plasma spraying through air, which is known to promote higher deposition efficiency and higher bond strength.
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