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Byline: L. Swadzba, B. Formanek, A. Maciejny The paper presents a review of heat-resistant coatings manufacture techniques for Ni-base superalloys. Modern techniques such as: Electron Beam Physical Vapor Deposition (EB-PVD), Low-Pressure Plasm Spray and modified (AltPt, Ale) aluminide coatings are described. Experimentally based results show the microstructure of Al-Cr and Al-Si coatings obtained by pack cementation technique. The coatings changes during their high-temperature service are utilized to determine the distribution of selected elements in coatings both before and after high temperature annealing. High hot-corrosion resistance of Si-modified aluminide coatings have been confirmed. Both microstructure and phase composition of the Al-Cr and Al-Si coatings depend on the chemical composition of the powder mixture applied in pack cementation technique. Chromium forms stable compounds with Al in the mixture while Si appears in the coating layers in a form of precipitation particles with elevated content of Mo, W, Ti and Cr. The Al-Si coatings show high hot corrosion resistance.

Byline: G. Dercz, K. Prusik, B. Formanek, L. Pajak The studied composite powder of high corrosion resistance was prepared using the Self-propagating High-temperature Synthesis (SHS) process. The as-prepared material was crushed and was subjected to a milling process by high-energy attritory mill for two and ten hours. The powder morphology was analysed through the Scanning Electron Microscopy (SEM) method. The structure investigations were performed using the SEM and XRD methods. The presence of Cr7C3, FeCr and FeO phases, besides the most desired FeAl(Cr), Cr3C2 and TiC ones, was noted. It was found that the FeAl(Cr) phase is of the ordered B2-type structure and the ordering degree diminishes with the increase of milling time. The crystallite size of this phase, both in the as-prepared state and after the milling process, is in the nanoscale. The crystallite size of the FeO phase diminishes to 75 nm in the sample ground for 10 h, whereas those of the other phases are above 100 nm for the as-prepared and ground samples.

Abstract: The process of obtaining cast aluminium composite of dispersive structure and hybrid reinforcement has been presented in the article. An Aluminium alloy (AlMg2) was modified with a powder mixture which, when in reaction with aluminium, reinforced the matrix with intermetallic phases and aluminium oxide. According to the technological conception, an assumption was made, that the cast composites would be produced in technological procedure shown in Fig. 1. The reinforcing phases were using Fe–Ti–Al powder mixtures with aluminium oxide formed in a self-propagating high-temperature synthesis (SHS). The structure and phase composition of the composite powder used for the matrix alloy modification are shown in Fig. 2. A composite alloy Al–FeAl–TiAl–Al2O3 was produced by casting method (gravity casting, mechanical mixing) after which its structure was determined. It was assumed that the final product of the applied production process will be an aluminium composite with hybrid reinforcement, consisting of Fe–Al and Ti–Al intermetallic phases and aluminium oxides. Optical microscopy, electron scanning microscopy and X-ray phase analysis were used to characterize the microstructure of the composites produced. Presence of aluminium, Al3Ti and Al13Fe4 phases and dispersed Al2O3 was confirmed in the composite by XRD method. The dispersion structure and phase composition of the composites are presented in Figs. 3–6. The composites formed in an in situ reaction constitute a newer generation of casts, in which dispersion reinforcement is obtained in the form of intermetallic and ceramic phases coherent with the matrix, very often below 1μm in size. The designed process allows for the structure modification of the applied casting aluminium alloys in different technological variants. [Copyright &y& Elsevier]

Abstract: The Ni(Cr)–TiC–Cr3C2–Cr7C3 composite powder was prepared by SHS (Self-propagating High-temperature Synthesis) process using elemental powders as starting materials. As-prepared powder was ground by an attritorial mill up to 10h. Micrographs and diffraction patterns were obtained using TEM. The X-ray diffraction data were analyzed by the Rietveld method and Toraya procedure. The Rietveld method was applied in the determination of phase abundance using Hill and Howard approach. The parameters of diffraction line profiles were analyzed by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed using Williamson–Hall method. It was stated that the crystallite size of Ni(Cr) phase diminishes to nanoscale after 5h milling whereas the crystallite size of the other phases is still above 100nm for applied milling time. [Copyright &y& Elsevier]

Abstract: The NiAl–TiC–Al2O3 composite powder was prepared by self-propagating high-temperature synthesis (SHS) process using elemental powders as starting materials. As-prepared powder was ground by a high-energy attritorial mill for up to 40h. The X-ray diffraction methods were used for the structure analysis of the as-prepared and ground samples. The Rietveld method was applied for the verification of the qualitative and quantitative phase composition of the studied material. The parameters of diffraction line profiles were determined by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed by Williamson–Hall method. It was found that during high-energy milling a significant decrease of crystallite size is observed only for NiAl phase. The crystallite size of this phase diminishes to 17nm when the milling time rises to 40h. [Copyright &y& Elsevier]