In the present contribution a number of porous materials has been investigated with various porosities (75 % < ψ < 93 %), mean pore diameters (360 < δ50 < 50,000 nm), and pore size distributions which are partly narrow and partly wide spread. The effective thermal conductivities have been measured between 500 and 1000 K in nitrogen, helium, argon and a nitrogen/hydrogen mixture (60/40 mol-%). Results are presented for the measured effective thermal conductivities with a strong effect of the kind of gas. For data evaluation, models available from the literature have been analyzed with respect to their ability for conductivity conversion from one gas to another. Suitable equations have been applied to the measured data, and agreement of measured and converted data has only been found in case of big sized pores. The deviations increase for smaller pore diameters and even stronger in cases of wide spread pore size distributions. A simple evaluation based on the Knudsen number corrected gas conductivity proved to be not successful in the latter case. These results are discussed in the light of the coupled effects of pore size, pore size distribution, accommodation coefficient and mean free path of the various gases.

The results of an inter laboratory comparison of thermal conductivity, thermal diffusivity, specific heat capacity, and thermal expansion measurements on austenitic stainless steel in the temperature range between 20 and 1000°C are presented here. Mean values are presented for the physical properties studied. Reliable relative expanded uncertainties can be stated for the properties determined, which were achieved by applying good measurement practice, i.e., 3% for thermal expansion, 5% for specific heat capacity and thermal diffusivity, and 6% for thermal conductivity. The mean values derived from this intercomparison agree well with the results of a previous intercomparison in 1990.

The laser-flash method is used to determine the thermal diffusivity of HVOF sprayed WC-Co(Cr) and Cr3C2-Ni20Cr as well as APS sprayed Cr2O3 and electroplated hard chromium coatings in the temperature range between RT and 600°C. Additionally bond and/or corrosion protective coatings like Ni5Al, Ni20Cr and 316L are characterized taking into account the different manufacturing methods twin wire arc spraying, HVCW and HVOF. With respect to the application example of drying rollers in paper industries the Taber-Abraser wear test is applied to evaluate the wear resistance. Finally the coatings are characterized concerning their corrosion resistance by salt fog test and by exposure to humid SO2 environment. For WC-CoCr feedstock the effect of carbide size and micro hardness on thermal, wear and corrosion properties are studied. WC-CoCr coatings with maximum micro hardness and fine carbides show the best thermal conductivity. The use of coarse carbide feedstock permits manufacturing of coatings with the highest resistance against dry abrasive wear, but the protective function depends severely on the processing conditions.

There is a variety of components, which are subject to high wear and/or corrosion stress on the one hand and are used to transfer heat on the other hand. Two examples are drying cylinders in paper production and condensing boilers. Up to now there are no data available for the thermal design of thermal spray coated components except for some MCrAlY and thermal barrier coatings for turbine applications. Also guidelines for the optimization of thermally sprayed coatings concerning heat transfer including the effect on the wear resistance are missing. HVOF sprayed cermet coatings are widely used for combined wear and corrosion protection these days. In addition to WC-CoCr 86 - 10 4 and 75 Cr3C2 - 25 Ni20Cr conventional Ni5Al and Ni20Cr bond coats are evaluated concerning their thermal conductivity in the range between room temperature and 600 °C. Also the thermal contact resistance is determined depending on the substrate material: mild steel S355J2G3 (1.0570), grey cast iron GG25 (0.6025) and austenitic stainless steel X5CrNi18-10 (1.4301, AISI 304). The applied Laser- Flash method requires knowledge of the heat capacity, thermal expansion and density, which are determined before. HVOF spraying has only negligible influence on the heat capacity of WC-CoCr feedstock, as the temperature depending functions are almost identical. The use of spraying feedstock with average WC particle sizes of 800 nm, 3 µm and 5 µm permits to investigate the influence of the specific surface area of the hard phases both on the thermal conductivity and wear resistance. Furthermore the influence of the coating porosity is determined. In accordance to the drying cylinder application the wear resistance is determined by Taber-Abraser wear tests. Bond coats are produced by HVOF, HVCW and arc spraying and compared concerning microstructure and thermal conductivity. A comparison to the properties of electroplated hard chromium coatings is drawn.

zHigh-temperature thermal conductivity of insulating material is usually measured by application of the steady-state calorimeter method or the transient hot-wire method. However. when applied to non-isotropic materials, the methods yield results which show systematic differences depending on orientation of the material during the measurement. In this contribution results are presented for one and the same material measured between room temperature and 1300 °C in all three instruments (according to the steady-state plate, the steady-state cylinder, and the transient hot-wire methods). Additional experiments are carried out in these instruments with various fibre orientations. Differences between the measured conductivities are found to exceed 100% in the high-temperature range. The results are discussed and supplemented by raster electron microscope (REM) and differential thermal analysis (DTA) of the fibre material and numerical studies of the temperature fields inside the facilities.