Papers by Author: Karl Maile

Abstract: High efficiency steam power plants are planned to operate at temperatures higher than 700°C and at a pressure of up to 350 bar. Due to this increase of the steam parameters, Ni-based alloys are required for constructing these plants. Materials testing - based on appropriate manufacturing and design criteria - is necessary in order to have a reliable data base of the relevant design characteristics. Additionally, a better understanding of the specific material behaviour under service like loading conditions for the evaluation of possible damage mechanisms is essential. This paper describes research on the behaviour of thick-walled power plant components made of Alloy 617 mod. and Alloy 263. Results from basic qualification programs with standard specimens including welded joints show the applicability of the materials. Results from creep rupture tests of base material and welded joints and microstructural investigations to obtain information on precipitations and dislocations in the virgin and aged conditions are presented. Information on the influence of chemical composition on creep rupture was obtained by analysing creep rupture data sets.

Abstract: This paper reflects our R&D results in the field of functionally graded coating processes. For industrial applications a special architecture for coatings is necessary: because the surface has to withstand environmental attacks, specific physical and mechanical functions and characteristics are required. In the interface region to the substrate additional stresses and strains occur due to the different materials combined. Consequently, the coatings have to be chemically and mechanically adjusted to the substrates. For this challenging problem, a concept named Materials Adapter has been developed within the frame of different research programs at MPA. For optimisation of the interface region an ion bombardment-activated inter-diffusion process ("ion mixing") was employed by using ion assisted electron beam PVD (IA EB PVD). Several Cr, Ti, Al and Zr coatings have been produced. An automated precursor inlet has been installed for CVD processes to obtain preset composition profiles for graded systems. Especially multilayer stacks of PyC-SixCy-SiC-Si3N4-Al2O3 have been deposited in a single growth process. The structure and composition of the coatings and interfaces were investigated by XRD, AFM, SEM, EDX, EPMA, ESCA and the micro-Raman spectroscopy. The characterisation confirms the gradual transition between Si and Cr, as well as between Cr and Al deposited by IA EB PVD and between C and Si grown by CVD.