Subject of this article are the results of gradient tubes analysis (material of the shell: 347H, material of the body: 11CrMo9-10) based on Amec Foster Wheele specifications requirement. The aim of the analysis was the determination of mechanical and technological properties of gradient tubes in order to install the gradient tubes in a commercial boiler. The NDT, outer shell thickness measurement, chemical analysis, tensile testing at 20°C and at elevated temperatures, flattening test, leak tightness test and metallographic examination of longitudinal and cross sections were used to prove the quality of gradient tubes. For this contribution, the gradient tubes (38mm outer diameter, 5mm wall thickness which austenitic shell is ~ 0,8mm thick) made by BENTELER were used.The work was done within the project GRAMAT supported by EU Research Fund for Coal and steel (www.gramat.org). The projects main aim is to acquire knowledge necessary to develop new cost-effective manufacturing technology of boiler tubes made from semi products with through thickness gradient chemical composition, tailored to carry both creep loading (low alloyed body) and fireside corrosion (high alloyed shell). Gradient tubes for the project are manufacturing in production facilities in BENTELER – Germany and PODBREZOVA IRONWORKS – Slovak Republic from semi products manufactured by unique casting technique (ŽDAS – Czech Republic); and to be tested by Amec Foster Wheeler – Finland in selected biomass boiler.Keywords: gradient tubes, alternative fuel-power, mechanical properties
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