THERMODYNAMIC MODELLING OF INTERDIFFUSION

IN Fe-Co AND Fe-Ni BONDS

Matej Pašák

Main term of diffusionMain 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.

Diffusion bondingDiffusion 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.

EXPERIMENTAL PARTEXPERIMENTAL PART

Selected materials for samplesSelected materials for samples

Material Label [wt. %]

Cobalt Co 99.99

Nickel Ni 99.99

interstitial free steel IF Fe - 99.4

austenitic stainless steel 18/10

Fe – 68.81

Cr – 17.7

Ni – 11.11

Experimental samples preparationExperimental samples preparation

Bonding: 7x7mm; 5Kg; 0.1 MPa; 1100°C; 20 hours

Heat treatment ofHeat treatment of samples samples

Simplified diagrams showing annealing conditions of samples

AnnealedAnnealed samplessamples

Annealed at 1000 hours for 1000 °C

Diffusion profileDiffusion profile

Measured diffusion profilesMeasured diffusion profiles

DICTRADICTRA

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.

Calculated diffusion profilesCalculated diffusion profilesCo Fe

COMPARISONCOMPARISON

700 700 °°CCFe-18Fe-18//1010

CaclucatedCaclucated

MeasuredMeasured

CaclucatedCaclucated

MeasuredMeasured

8800 00 °°CCFe-18Fe-18//1010

CaclucatedCaclucated

MeasuredMeasured

101000 00 °°CCFe-18Fe-18//1010

CaclucatedCaclucated

MeasuredMeasured

101000 00 °°CCFe-Fe-CoCo

CaclucatedCaclucated

MeasuredMeasured

101000 00 °°CCFe-Fe-NiNi

CCONCLUSIONONCLUSIONComparison 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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