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F. Warchomicka:
"Characterization of inset cylinders for a detonation chamber";
Report No. Mai, 2011; 22 pages.

Pure nickel and nickel chromium alloys, a cobalt alloy and an aluminium alloy with ceramic coating were investigated after gas detonations at 60bar. Microstructural investigations were carried out in different places of the inset cylinder in order to observe thermal shock damage on the surface and the crack depth after different numbers of detonations. A strong influence of the cooling system on the damage was determined, observing an increment of damage at the bottom of the cylinder, where
there is no direct water cooling. The finishing of the surface influences drastically the crack inititiation, observing cracks on the surface in line with machinig groves. The pure nickel cylinder showed less damage than the other materials. There is some correlation with the grain size and the thermal conductivity. The aluminium alloy plasma coated with aluminium oxide shows good thermal shock resistance in zones were the water cooling was operating. In general all the specimens were affected by the melting of the steel part below the inset cylinder. Drops of steel were sprayed onto insetin the whole wall of the specimen. This deposition of steel was increasing with the subsequent detonation experiments.

microstructure, thermal shock damage, modified High Energy Rate Forming