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MCrAlY materials are widely used as bond coats for thermal barrier coatings on turbine blades. The aim of this work is to improve mechanical properties and wear resistance of thermal sprayed NiCoCrAlYcoatings by strengthening the coating with hard phase particles. In order to retain the effect of the dispersion reinforcement at high temperatures, the use of temperature-stable oxide hard phases such as ZrO 2 -Y 2 O 3 is necessary. To realize this new material structure, the high-energy ball-milling process is applied and analyzed. The mixture ratio between NiCoCrAlY and ZrO 2 -Y 2 O 3 was varied between 5 and 10 wt.% ZrO 2 -Y 2 O 3 . The influences of the milling time of the high-energy ball-milling process on the distribution of the hard phases in the metal matrix were analyzed. After spraying with a HVOF system the mechanical properties of the coatings are measured and compared with conventional NiCoCrAlY coatings.

In previous work, a thermal spray multilayer system consisting of Zirconia (ZrO 2 ) and MCrAlY top coat showed promising results regarding the oxidation behavior of the Gamma Titanium Aluminides substrates tested, which encouraged further research activities. Diffusion of substrate material was successfully inhibited by a ceramic Zirconia coating. A building up of a dense and stable oxide layer could be achieved by additional application of an MCrAlY top coat, leading to improved oxidation resistance and thus showing feasibility. In this work the main focus for development was put on enhancing adhesion and lowering residual stresses of the coatings in order to allow long term and cyclic testing without delamination taking place. Being a very brittle material, Gamma Titanium Aluminides require special surface treatment to enable roughening which is crucial for a strong mechanical bond between substrate and coating. Alternatives to conventional grit blasting as a standard preparation method were investigated. These were micro-abrasive blasting and blasting at elevated temperature (L300 -550 8C) to allow a more ductile behavior. The paper will highlight the implications by means of these measures and will also show the present development status of the multilayer system.

Ferrites are iron containing, non-conducting ceramics, which exhibit magnetic properties. One of the most common is (Ni,Zn) 1 Fe 2 O 4 . Bulk ferrites are typically made by conventional ceramic sintering. However, manufacture of thick coatings is of growing interest, and deposition by thermal spraying is potentially attractive. The present paper reports work on the development of (Ni 0?549 Zn 0?333 Co 0?028 Mn 0?049 )O 0?958 Fe 2 O 3 based powder feedstock by self-propagating high temperature synthesis and coating deposition by both air plasma and high velocity oxy-fuel spraying. The results obtained show that some decomposition of the ferrite material occurred with the loss of zinc and oxygen. The Zn loss is dependent to a large extent on the surface/volume ratio of the powder used in spray deposition. The influence of the spraying technique on the electromagnetic properties was also measured and compared to bulk ferrite materials. The air plasma sprayed coatings showed similar absorption coefficient compared to the bulk ferrite material at high frequencies (,3 GHz).

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