1. THERMODYNAMIC MODELLING OF INTERDIFFUSION IN Fe-Co AND Fe-Ni BONDS Matej Pašák

2. Main term of diffusion Diffusion is movement of mass. Transport particles from a region of higher concentration to one of lower. It is random thermally activated jumping of atoms in a solid. Jumps are bigger than lattice parameter. Interdiffusion is diffusion of atoms of one element into another element.

3. Diffusion bonding Welding process that faying surfaces are brought into sufficiently close contact using an applied pressure at elevated temperature to allow bond formation by atomic interdiffusion across the joint interface without melting.

4. EXPERIMENTAL PART

5. Selected materials for samples MaterialLabel[wt. %] CobaltCo99.99 NickelNi99.99 interstitial free steelIFFe - 99.4 austenitic stainless steel18/10 Fe – 68.81 Cr – 17.7 Ni – 11.11

6. Experimental samples preparation Bonding: 7x7mm; 5Kg; 0.1 MPa; 1100°C; 20 hours

7. Heat treatment of samples Simplified diagrams showing annealing conditions of samples

8. Annealed samples Annealed at 1000 hours for 1000 °C

9. Diffusion profile

10. Measured diffusion profiles

11. DICTRA DIffusion Controlled TRAnsformations The DICTRA software is based on a numerical solution of the multicomponent diffusion equations. Diffusion simulations are based on assessed kinetic and thermodynamic data, which have been stored in databases.

12. Calculated diffusion profiles Co Fe

13. COMPARISON

14. 700 °C Fe-18/10 Caclucated Measured

15. Caclucated Measured 800 °C Fe-18/10

16. Caclucated Measured 1000 °C Fe-18/10

17. Caclucated Measured 1000 °C Fe-Co

18. Caclucated Measured 1000 °C Fe-Ni

19. CONCLUSION Comparison between the experimental and the calculated diffusion profiles shows they are not the same but very similar. The agreement between measured and calculated trends is better at higher temperatures. For better qualitative description of the results, finding proportional coefficients between measured and calculated trends seems to be suitable.

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