Wachstum und Annihilation von Mikroporen in einkristallinen Nickelbasis-Superlegierungen während Homogenisierung und heiß-isostatischem Verdichten
Zusammenfassung der Projektergebnisse
In the 1st main topic, porosity growth during homogenisation, the main growth mechanism was identified. It is the Kirkendall effect, operating during the solution of eutectic areas in the interface eutectic/matrix. The diffusion coefficient of Re in Ni was measured in the temperature range 1050 - 1350°C, which now allows to model the multicomponent interdiffusion during eutectic solution. In the 2nd main topic, porosity annihilation during HIP, TEM investigations showed, that the deformation around the pores is based on dislocation motion, not vacancy emission. The elastic properties and compression curves of CMSX-4 were measured up to 1300°C. These results were introduced into a finite element model for plastic pore closure and the kinetics of porosity annihilation was modelled. The calculated kinetics of pore closure is similar to the experimental result of interrupted HIP experiments, but needs further refinement. So physical understanding of pore annihilation now exists, but further work is need for extending the empirical database and for improvement of modelling. Future work, possible applications: 1st main topic. Diffusion modelling of eutectic solution. Experimental validation of modelling: measurement of kinetics of porosity growth and eutectic solution, concentration gradients around dissolving eutectic areas. 2st main topic. Additional mechanical tests at HIP temperatures (anisotropy, tests in tension, wider stress range) for refinement of the creep law used for modelling. Improvement of the pore closure model (e.g. with surface tension). Profound investigations of the effect of HIP on the mechanical properties of single-crystal superalloys, including the 4th generation superalloy VGM4. Possible fields of application are development, processing and modelling of single-crystal superalloys.
Projektbezogene Publikationen (Auswahl)
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Characterisation of the Structure of Single-Crystal Nickel-Base Superalloys, Materials Science Forum, Vols 638 – 642 (2010) pp. 2227-2232
A. Epishin, T. Link and U. Brückner
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Creep damage of single-crystal nickel base superalloys: mechanisms and effect on low cycle fatigue, Materials at High Temperature, Vol. 27 (2010) pp. 53-59
A. Epishin, T. Link, H. Klingelhöffer, B. Fedelich and P. D. Portella
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Low cycle fatigue of nickel superalloy single crystals at elevated temperatures, Applied Problems of Strength and Plasticity, Russian Metallurgy, Vol. 2010, No. 10 (2010), pp. 941-947
E. R. Golubovskiy, I. L. Svetlov, N. V. Petrushin, S. A. Cherkasova and M. E. Volkov
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Models for the porosity growth and dissolution in single-crystal nickel-base superalloys, Materials Science Forum, Vols 297-301 (2010) pp. 187-192
B. S. Bokstein, V. A. Esin, A. O. Rodin and I. L. Svetlov
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Segregation in single-crystal nickel-base superalloys, Defect and Diffusion Forum, Vols 309-310 (2011) pp. 121-126
A. Epishin, I. L. Svetlov, N. V. Petrushin, Yu. V. Loshchinin and T. Link
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The influence of HIP on high temperature creep of single-crystal nickel-base superalloys, Deformation and Rupture of Materials, No. 3 (2011) pp. 28-32 (in Russian)
I. L. Svetlov, I. V. Ishodjanova, A. G. Evgenov and S. A. Naprienko
