The objective of this investigation is both to study the adherence and integrity of the coatings and to investigate a possible influence of surface modifications on crack initiation in the base material. The thermal cycle fatigue tests have to be performed with tubes made of austenitic steel, preferably AISI 316 LSPH, with outer surface coatings. An equipment for thermal fatigue testing has been developed. Yet, tubular specimens with a diameter of 60 mm, a wall thickness of 3.5 mm and a heated

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... ength of 150 mm are used. The experimental setup is described in PSM 3.9. First tests have been made with tubes of the reference material 1.4436 and outer surface coating. The calculated strain range in the coating was about 0.25 %. The cracks initiated at the inner side of the tube as in tests without coating. After the test no cracks were visible on the surface of the coating. The integrity was good. Four more specimens of this material were fabricated still without coating and will be delivered for coating. Further tests are planned with the same kind of tubes as in PSM 3.9 made of AISI 316 LSPH. By choosing thicker tube walls higher strain amplitudes in the coating are expected. To buy tubes of this material and geometry different dealers were contacted. No tubes with SPH fabrication specification were found in sufficient quantities. Different 316 L tubes were investigated about their chemical composition. Measurements to obtain the parts of 8-ferrit and nitrogen were performed. Specimens with chemical composition near to the SPH specification are now in fabrication to compare the fatigue behaviour with 316 LSPH. Parallel the fabrication of tubes from raw material was ordered. T. Fett W. Hartlieb J. Neumann B. Schinke 1200 oc, 1.2-1.6 x 1026 n!m2) and PHENIX-MAT 6 (Phenix-Marcoule, about 500 oc, 30 dpa). Bendingtests to determine UBS on about 100 specimens ofHIP-SiC and CVD-SiC from CERAM-D217-1 are being started.