Several model Fe- and Ni-based alloys with increased content (up to 30 at.-%) of protecting scale forming elements were developed. High temperature corrosion resistance of bulk alloys as well as thermally sprayed coatings and welded overlays were investigated under the waste power plants simulated atmosphere (500 °C, 100 hours, 75N 2 -20O 2 -4.9Ar-0.1Cl 2 ). Arc and HVOF spraying as well as PTA overlay welding were used to produce the coatings. After an exposure the samples were examined with electron probe micro-analysis (EPMA). It was shown that the protection behaviour of overlay welds depends on the content of alloying elements, although the last is limited because of weldability decrease by high alloying level. High temperature corrosion resistance of thermally sprayed coatings is determined by their porosity, which can be varied over a very broad range depending on the applied spray method. The arc sprayed coatings need an additional post-treatment to close a porosity. Two methods were applied, pre-oxidation treatment in the air and sealing with the commercial sealant. Newly developed iron-based coatings with increased aluminium content (< 20 wt- %) sprayed with HVOF-spraying with powders obtained by means of high energy ball milling demonstrate high corrosion resistance. Selected coatings were evaluated for 1000 h exposure under chlorine-containing salt deposits at the higher temperature (600 °C).

The heat produced by incinerator plants can be used to produce electricity and district heating. Metallic components, e. g. heat exchangers, are exposed to a highly corrosive atmosphere. Gases with particularly high chlorine contents lead to the very quick wear of the base material and define the service time and are the main reason for high maintenance costs. Spraying a corrosion-protective coating on conventional steel gives the possibility to improve the performance of the surface significantly. Due to its easy handling and low operating costs, wire arc spraying has become one of the most established processes. The thermal spray Ni- and Co-based coating alloys are state of the art. The substitution of these materials by Fe-based alloys will lead to a noticeable economic benefit. The latest research activities proved that the addition of silicon raises the corrosion resistance in comparison to FeCr- and NiCr-based alloys. In order to verify the potential of these materials, flux-cored wires with different compositions were manufactured and were applied by means of arc spraying. Subsequently, corrosion investigations were conducted on the specimens in an atmosphere containing chlorine.

Due to its easy handling and low operating costs, wire arc spraying has become one of the most established processes for applying protective coatings to components used in waste incineration plants. This paper discusses the development of relatively low-cost Fe-Cr-Si coating materials for incinerator applications and the corrosion and wear properties that have been achieved using conventional arc spraying methods.

Intermetallic TiAl coatings were applied to ferritic steels using plasma and HVOF spraying methods. The specimens were then placed in reducing sulfidizing atmospheres for high-temperature corrosion testing. This paper describes the experiments that were performed and presents and analyzes the results. In general, for the reasons given, the coatings performed better in an Ar-H 2 -H 2 S-atmosphere than in one containing CH 4 . Paper text in German.