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E. Aschauer, P. Felfer, C Macauley, M. Arndt, H. Bolvardi, P. Polcik, P.H. Mayrhofer, H. Riedl:
"Influence of Ti on the phase evolution of magnetron sputtered PVD deposited Mo-Si-B coatings";
Poster: EMRS Spring Meeting 2019, Nizza; 2019-05-27 - 2019-05-31.

Based on their high temperature strength, outstanding creep resistance as well as excellent oxidation resistance, Si and B alloyed refractory metals such as the Mo Si B system are promising candidates for next generation turbine materials. Here, the poor oxidation resistance of Mo¬ - dominated by the formation of volatile MoOx (so called pesting) - is impeded by the generation of a dense, glassy like borosilicate-based layer. However, providing a proper B/Si ratio is crucial for enhancing the oxidation resistance. The phase combination of bcc-Mo, c-Mo3Si, and T2-Mo5SiB2, as occurring in the three phase field known as Berczik Triangle, provides the ideal ratio of boron and silicon to form a highly stable borosilicate-based scale.

To access these interesting properties for further bulk materials, PVD is a proper technique to deposit Mo Si B thin films. However, during PVD deposition, the kinetic input during film growth limits the formation of crystalline phases within the Berczik triangle, especially at typical deposition temperatures. Alloying titanium is known to stabilise in particular the T2-Mo5SiB2 phase for bulk alloys.

In this study, we present a detailed analysis of the Mo (Ti) Si B system deposited by magnetron sputtering, varying the Ti content as well as the deposition parameters in a wide range. The obtained coatings were characterised in the as deposited state and upon annealing, using thermal analysis, XRD, as well as high resolution techniques such as TEM and APT.

Project Head Helmut Riedl:
CDL-SEC