Diffusive Interaction Between Ni-Cr-Al Alloys
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E interdiffusion in multicomponent systems controls many technological processes, such as nitriding, carburizing, and aluminizing. It can, however, also appear as negative phenomenon, causing degradation of protective coatings and alloys. A problem is that diffusion in multicomponent systems can be followed by a formation of multiphase zones of complex morphologies. Such zones can grow in ternary and more component systems which are allowed by Gibbs phase rule. The diffusion in two- and multiphase zones differs from the diffusion in the single phase and can lead to the effects such as zigzag diffusion, horns at the diffusion path, and jumps of the concentrations without typical interphase boundary.[1,2] In this work, we study diffusion between single- and two-phase Ni-Cr-Al alloys. The alloys from this system are a basis for the development of numerous creep-resistant alloys. The interest in this system is prompted by the applications of nickel-based superalloys in gas turbines and jet engines working at high temperatures. These alloys have superior mechanical properties and high heat resistance at high temperatures.[3] The importance of the Ni-Cr-Al system is followed by numerous experimental and theoretical studies of the phase diagrams for this system.[4–19] Most of the KATARZYNA TKACZ-S´MIECH, MAREK DANIELEWSKI, DARIUSZ ZIENTARA, and MAREK ZAJUSZ are with the Faculty of Materials Science and Ceramics, AGH University of Science and _ Technology, 30-059 Krako´w, Poland. BOGUSLAW BOZEK is with the Faculty of Applied Mathematics, AGH University of Science and Technology, 30-059 Krako´w, Poland. KATARZYNA BERENT is with the ACMiN, AGH University of Science and Technology, 30-059 Krako´w, Poland. Contact e-mail: [email protected] Manuscript submitted August 26, 2016. Article published online March 9, 2017 METALLURGICAL AND MATERIALS TRANSACTIONS A
research is confined to Ni-rich corner at high temperatures, i.e., above 1273 K (1000 C). Due to experimental difficulties, the bibliography dedicated to diffusion in Ni-Cr-Al alloys is limited, and there are only few experimental results.[20–27] Over forty Ni-Cr-Al diffusion couples, in c|c + b multiphase couples, were experimentally studied by Nesbitt and Heckel.[26] The samples were annealed at 1373 K and 1473 K (1100 C and 1200 C) for 100 hours, and the concentration profiles and diffusion paths measured. The measurement was made in c phase only. The concentrations and diffusion path in two-phase zone were approximated from the terminal compositions. As follows in Reference 22 experimental and simulated results of simulations of interdiffusion in c + b|c couple were presented. The agreement between calculated and measured diffusion paths was, however, very weak. In Reference 28, DICTRA software was applied and interdiffusion in c + b|c simulated. The simulated and measured diffusion paths remained in good agreement. The authors revealed the recession of two-phase zone which agreed with experiment. Unfortunately, the authors have not revealed the kinetic coefficients used in the calculation
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