A new concept of thermal barrier coating (TBC) system is presented, based on a metal‐glass composite (MGC). Coatings of metal‐glass composite can be deposited by vacuum plasma spraying and slip casting with a subsequent sinter step. In this TBC system the thermal expansion coefficient depends on the metal‐glass ratio. It is chosen in such a way that the thermal expansion coefficient of the composite is close to the one of the substrate. This leads to reduced thermal stresses and hence improved thermal cycling life times. Because of the low thermal mismatch, coatings of more than 600 μm thickness can be realized. Another advantage of the gas tight composite coatings is their ability to protect the bondcoat from severe oxidation. Correspondingly, long life times have been found for these TBCs in oxidation tests. Also good results were found during thermal cycling tests. Furthermore some aspects of the microstructure evolution of the composite during heat treatment are described.

and .stationary engines operate on fuels that contain corrosive elements, with the result that some highly loaded combustion chamber components must be replaced frequently. Märkisches Werk, GmbH (MWH) has pioneered the development of mineral-metal, multiphase coatings to protect valves and other highly loaded engine components against hot-gas corrosion. Mineral-metal, multiphase coatings are a unique and innovative approach to improving hot-gas corrosion resistance in a cost-effective manner. In general, these coatings combine the beneflcial chemical and thermal attributes of ceramic coatings with the mechanical properties and substrate adhesion characteristics of a metal. Extensive laboratory and field trials have proven that MWH CrystalCoat protects heavy fuel oil (HFO) engine exhaust valves against hot-gas corrosion. It is projected that the newest coating formulation (CrystalCoat HT) will protect four-stroke HFO exhaust valves against hot-gas corrosion over their entire service life.

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In this article, the author poses and responds to a provocative question that has practically ceased to be asked in the field of thermal spraying of carbide coatings: Is the current worldwide trend of using only unmelted metal particles to form coatings (HVOF, HVAF and cold spray methods) correct, and is the deposition of completely melted powders (plasma spraying methods) really outdated? The results of high-speed plasma deposition of new carbide powders allowed the author to prove that only coatings from molten particles can solve the main problem of such coatings, namely the problem of permeability along the grain boundaries. Through the use of modern Axial III plasma torches combined with optimized fine-grained powders, it has been possible to create Cr3C2-NiCr as well as WC-Co-Cr gas-tight layers.

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