Results of computer simulations of long term service exposure for weldments of the CSN 15 128/P91 and SK3STC/P91 steels are presented and compared with corresponding results of phase and composition experiments. The welded material P91 (EU designation: X10CrMoVNb 9 -1) represents progressive chromium steel alloyed with molybdenum, vanadium, carbon, and nitrogen. The CSN 15 128 (13CrMoV 2 -5) material is low alloy Cr -Mo -V steel. The SK3STC alloy (12CrMo 10 -10) represents the consumable electrode material. The stability of the weldment microstructure is investigated at elevated temperatures (500 -700°C). The simulation method is based on the Calphad approach complemented with the theory of multicomponent bulk diffusion, local conditions of phase equilibrium, and the assumption that diffusion is the process that controls the rate of phase transformation. Signi cant phase pro les, concentration pro les, and phase transformation processes in the diffusion affected zone are simulated, investigated, and compared with experimental results. The potentially deleterious carbon depleted region inside each weld joint is discussed. The method described can be used to predict microstructure instability in weld joints. STWJ/374Keywords: low alloy steel, kinetic simulation Dr Sopous fek is in the Faculty

The paper presents results obtained during evaluation of dissimilar weld joints of creep-resistant steels. During high temperature exposure of dissimilar weld joints, alloying elements were redistributed across the weld interface. These diffusion effects can cause local changes of microstructure and have a direct effect on local mechanical properties in weld interface area. Carbon and nitrogen have the strongest influence on changes of mechanical properties of steels. . These local changes of mechanical properties have a strong influence on the reliability and the service live of the whole welded structures. The dissimilar joints of the austenitic steel/martenzitic steel type was studied. Laboratory weld joints were prepared and annealed at different temperatures for different time periods. Microhardness profiles across the weld interface were measured and the influence of long-term, high temperature exposure on the changes of local microhardness was evaluated. Results were compared with pseudo-binary phase diagrams and with the literature.

Nanostructured CoNiCrAlY bond coatings were deposited onto a Ni-based alloy (Inconel 718) by both HVOF and CGDS spraying techniques. Subsequently, the deposits were remelted by an electron beam up to depth of about 100 μm, which resulted in the removal of defects on the substrate to the bond coat interface. This paper examines the influence of the parameters used for EB remelting, including multiple remelting on the microstructural changes, phase modification and the final state of the coatings. The amount of porosity in the coatings and the surface roughness has been evaluated. Scanning electron microscopy and X-ray diffraction were performed in order to characterize the phase modification before and after the applied treatment. The results indicated that multiple remelting improved the coating in terms of porosity, surface roughness decrease, mechanical strength and chemical homogeneity. This study also demonstrates that the CGDS deposition represents a promising alternative for CoNiCrAlY bond coat manufacturing. Keywords: bond coat, CoNiCrAlY, cold gas dynamic spraying, HVOF spraying, EB remelting Nanostrukturirane prevleke na osnovi CoNiCrAlY so avtorji prispevka nanesli na podlago iz Ni superzlitine (Inconel 718) z dvema metodama napr{evanja; z zelo hitrim napr{evanjem kovinskih delcev v toku me{anice plinastega goriva in kisika (HVOF; angl.: High Velocity Oxygen Fuel) in tehniko dinami~nega napr{evanja v hladnem plinu (CGDS; Cold Gas Dynamic Spraying). Sledilo je takoj{nje pretaljevanje napr{enih prevlek z elektronskim snopom do globine pribli`no 100 μm, kar naj bi odstranilo napake nastale med napr{evanjem in izbolj{alo povezavo prevlek s podlago. V~lanku avtorji opisujejo vpliv parametrov uporabljenega pretaljevanja z elektronskim snopom, vklju~no z vplivom ve~kratnega pretaljevanja na mikrostrukturne spremembe, fazne modifikacije in kon~no stanje prevlek. Ovrednotili so poroznost izdelanih prevlek in poroznost njihove povr{ine. Izvedli so analize z vrsti~nim elektronskim mikroskopom (SEM; angl.: Scanning Electron Microscopy) in rentgensko difrakcijo (angl.: X-Ray Diffraction), da so lahko dolo~ili fazne transformacije pred in po obdelavi prevlek. Rezultati preiskav so pokazali, da ve~kratno pretaljevanje izbolj{a kakovost prevlek v smislu zmanj{anja njihove poroznosti in povr{inske hrapavosti, izbolj{a kemijsko homogenost in trdnost. [tudija je prav tako pokazala, da izdelava prevlek na osnovi CoNiCrAlY z CGDS postopkom lahko predstavlja alternativo drugim postopkom napr{evanja te vrste prevlek. Keywords: opla{~enje, CoNiCrAlY prevleke, CGDS -dinami~no napr{evanje v hladnem plinu, HVOF -zelo hitro napr{evanje kovinskih delcev v toku me{anice goriva in kisika, pretaljevanje z elektronskim snopom

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Thick Fe-Al deposits were produced by low-pressure cold spraying using heated air as the working gas. The coatings were isothermally annealed for two hours in Ar at temperatures from 250 °C to 750 °C. Changes in fracture behavior and microhardness were evaluated along with the microstructure and composition of newly formed phases. The results show that the evolution of intermetallic phases was driven by diffusion at temperatures above 550 °C. The new phases formed a hard skeleton that preserved the general shape of the samples during treatment despite the growth of external dimensions and porosity.