Oxidation calculations using TCNI6 database for Co based alloys Suzana G. Fries

Transkript

1 Oxidation calculations using TCNI6 database for Co based alloys Suzana G. Fries

2 2 The binaries

3 Co-Al-W Co-8Al-9W-2Ta γ/γ 500nm Courtesy of M. Göken γ -Phase Co 3 (Al,W) Stable (?) L1 2 Phase im Co-Al-W System Sato et al., Science,

4 Commercial databases for Ni(Co) superalloys The TTNI7 proprietary database already available in ICAMS. TTNi7 (Version 7.0, Jan. 2006) 22 elements included: Ni Al Co Cr Cu Fe Hf Mn Mo Nb Re Ru Si Ta Ti V W Zr B C N O The TCNI5 proprietary database is now available in the project. TCS Ni-based Superalloys Database, Version elements included: Al. Ar, B, C, Co, Cr, Fe, H, Hf, Mo, N, Nb, Ni, O, Pd, Pt, Re, Si, Ta, Ti, V, W, Zr (292phases in total) Extensive GAS mixture phase (Al, Ar and different species in the C-H-N-O system) Ordered and disordered bcc (A2 and B2/beta) and fcc (A1 and L12/γ ) phases are modeled with a two sub-lattice model using a single Gibbs energy curve which enables order/disorder transformations to be modeled All possible binary systems and most Ni-containing ternary systems have been assessed to the full range of composition 4

5 Project C6: Commercial databases, ternary Al-Co-W 1173 K TTNI7 N. Dupin, TCNI5 5

6 Project C6: Commercial databases, ternary Al-Co-W 1273 K TTNI7 N. Dupin, TCNI5 6

7 From John Ågren in CALPHAD 2013 LOGFILE GENERATED ON PC/WINDOWS NT DATE goto da def-sys fe cr ni o get goto p-3 s-c T=1173 p= s-c b(fe)=74 b(cr)=18 b(ni)=8 s-r-s o gas * 1E5 s-c mur(o) 0 c-e l-e SCREEN VWCS s-a-v 1 mur(o) step NORMAL pos s-d-a x acr(o) s-d-a y npm(*) * set-ax-ty x log plot SCREEN se-lab? f plot SCREEN s-sc x N 1e-14 1 plot SCREEN set-inter exit

8 A5 (Virtanen) Hochtemperaturoxidation einkristalliner Superlegierungen Ziele Frühstadien der Oxidbildung auf heterogenen Oberflächen (lokal aufgelöst) Charakterisierung der Oxidschichten mit Methoden hoher lateraler Auflösung Zusammenhänge Chemie & Mikrostruktur der Oberfläche / Initiierung und Wachstum von Oxidschichten Expertise und Vorarbeiten Verständnis von Elementarprozessen der HT-Oxidation Korrosion, Elektrochemie, Oberflächenanalytik HT-Oxidation von Ni-Basis-Superlegierungen erste HT-Oxidationsuntersuchungen an polykristallinen γ/γ -gehärteten Co-Basis-Legierungen Beispiel: Einfluss von Bor auf die Oxidation von Co-Al-W-B Legierungen in Luft bei 800 C TG: Bor verbessert die Oxidationsbeständigkeit. ToF-SIMS: B-Anreicherung in der inneren Oxidschicht. 8 Weitere Untersuchungen zu Mechanismen erforderlich!

9 A5 (Virtanen) Hochtemperaturoxidation einkristalliner Superlegierungen Projektplan Oxidation an neuen γ/γ -gehärteten Co-Legierungen (vom Projekt B3) Initiierung der Oxidbildung auf heterogenen Oberflächen Lateral aufgelöste Oberflächenanalytik & TEM kritische Substrateigenschaften zur schnellen Bildung einer Barriereschicht Wachstum der Oxidschichten Thermogravimetrie & Charakterisierung O 18 /O 16 sequentielle Oxidation & ToF-SIMS Elementarmechanismen der Oxidation Weitere Fragestellungen im SFB-TR Wachstumsspannungen Oxidation vs. thermische Ermüdung beschichtete Systeme 9

10 10 L. Klein and S. Virtanen from Erlangen A. Zengedani and M. Palumbo from Bochum

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12 First approach for thermodynamic modelling of the high temperature oxidation behaviour of ternary γ'-strengthened Co-Al-W superalloys L. Klein 1, A. Zendegani 2, M. Palumbo 2, S.G. Fries 2, S. Virtanen 1 Corrosion Science Co-9Al-9W alloy (values in at %) was isothermally oxidised for 500 h at 800 and 900 C in air. Results reveal that the calculated oxide layer sequence (Thermo-calc, TCNI6) is in excellent agreement with the formed oxide scales on the alloy surface. Furthermore, prediction of the influence of oxygen partial pressure on Al 2 O 3 formation is presented. The modelling results indicate pathways for alloy development or possible pre-oxidation surface treatments for improved oxidation resistance of the material. 12

13 Co-Al-W 13

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17 Suggestion to Thermocalc: to include CoWO4 in the database. ternary spinel phases, such as CoAl2O4. However, since CoWO4 is not included in the current database, calculations do not take this phase into account. 17

18 18 Ake in Aachen