MAX phase materials belong to a group of ternary ceramics. They can be described as nanolaminates of metal (M) carbides or nitrides (X) separated by a single layer of A-atoms. This structure, with a relatively weak bonding between the M and A atoms compared to that of M-X bonds, gives rise to a previously unforeseen combination of metallic and ceramic properties, which makes these materials highly functional. For instance, MAX phases possess high thermal and electric conductivity like metals and can be machined, but like ceramics they have good oxidation resistance. The unusual properties of these materials have attracted a great deal of technological interest and inspired researchers. So far, MAX phase materials have been produced in bulk form or as thin films by sputtering. For many new applications alternative deposition processes must be applied.
In the present work we have investigated the possibility of producing MAX-phase coatings using spraying of Maxthal 211 (Ti2AlC) powder by high velocity oxy fuel. The microstructure of the coatings was investigated using both scanning electron microscopy and transmission electron microscopy. Studies show the presence of dense and thick films with morphology that at low magnification resembles that which is typical for thermally sprayed coatings. A closer look on the microstructure of the coatings reveals however the presence of very small (100 nm in size) grains embedded in the original powder grains. The composition of these small grains is different from Ti2AlC. Moreover, chemical analysis using EDX reveals that high amount of oxygen is incorporated into the coatings. Further discussion of the results will be presented. |