In a BRITE-EURAM Project gas shroud devices were developed for arc-wire and air plasma spraying processes to obtain cost effective coatings with high density, low defect contents and high corrosion resistance. To test the two devices FeCrAl, NiCrAl and NiCrTi coatings sprayed by shrouded arc were studied for boiler application; AMDRY 995 coatings sprayed by shrouded plasma were analysed for gas turbine blades. In this paper the results are presented of the extensive characterization performed by CESI on the coatings produced with the innovative techniques developed by the other partners. The coatings were sectioned and analysed by metallography and image analysis to determine oxide and porosity contents (total defect levels were less than 5%). Hardness and adhesion were measured following the ASTM standard procedures. On FeCrAl, NiCrAl and NiCrTi coatings sprayed by shrouded arc-wire technique both thermal cycling and corrosion tests were performed. A sulphidizing gaseous atmosphere was used to simulate boiler environment burning sulphur rich fuel as Orimulsion. The corrosion behavior after 1000h at 450°C resulted to be as good as that of an HVOF sprayed similar coating. Moreover coated tubes survived to thermal cycling tests without any delamination. Hot corrosion "Dean tests" were performed on AMDRY995 coatings sprayed by shrouded plasma onto two Ni-base superalloys (Ud 529 and In738). The environment was typical of hot parts in gas turbines; the corrosion resistance results after 1750h at 850°C were comparable to those typically obtained on the same material sprayed by vacuum plasma spray technique. The applicability of the shrouded plasma technique to the field of gas turbines was confirmed.

In this study, several thermal spray coatings and reference materials were evaluated for potential use in biomass co-fired boilers. The coatings were applied to T92, A263, and X10Cr13 substrates by HVOF and wire-arc spraying using powder (IN625, FeCr, NiCr) and wire (NiCrTi) feedstocks. Coating samples were examined then tested for 5900 h in the superheater area of a fluidized bed boiler burning a mixture of wood, peat, and coal. The corrosion behavior of the coating and reference materials is reported in the paper and the underlying corrosion mechanisms are discussed.

Arc spraying has always been the most cost-effective way of thermal spraying metal alloys but oxide content and degradation of the alloy by loss of particular alloying elements have limited quality of the coatings. In this paper a process is described which greatly reduces degradation and improves coating density and oxide content. Corrosion behaviour both in aqueous and high temperature environments is markedly improved. For aqueous applications coatings of Inconel 625 were tested in a potentio-dynamic cell and by salt spray testing to evaluate both the inherent properties and the permeability of the coating and significantly improved behaviour was found in both cases. For high temperature corrosion, samples of FeCrAl were tested in air and in a sulphidising environment with and without thermal cycling. Coatings of NiCrAl and NiCrTi were also examined. The coating types and test regimes were aimed at specific practical applications such as fireside corrosion in boilers and waste incinerators, hot oxidation of flare stack burners etc. In the aqueous situation valves and process vessels are being examined as candidate applications for Inconel 625 coatings.

The goal of this work is to develop a flame sprayed NiCr-Cr 3 C 2 coating that resists oxidation, corrosion, and erosion in boiler environments and to assess the influence of Cr 3 C 2 fraction and sealing on coating performance. In the experiments, NiCr cermet alloys with different proportions of chromium carbide were applied to boiler steel substrates by means of subsonic velocity flame spraying and some of the coatings were sealed with a silicon resin. The paper describes the various tests performed and presents the results. Paper includes a German-language abstract.

The current situations of thermal spraying materials in China are described in this paper. The thermal spraying technology in China has a great progress over tens of years. More than one hundred varieties of material products are serving in thermal spraying industry now, which are grouped into three kinds: powders, wires and rods. And technologies for producing alloy or ceramic or composite powders, alloy or cored wires, and oxide ceramic rods are applied to large-scale production. Many research and development works on advanced materials for thermal spraying are carrying out in recent years. They show that the general tendencies of thermal spraying materials in China are composite or low-impurity component, ultrafine or nanosized microstructure, high properties, as well as specialized and systematized applications. Thermal spraying materials have great prospects in China.