Microstructure simulation of reactive air brazed joints

  Wetting test with Ag16Cu solder on BSCF, soldered at 1000°C for 6 min in air Copyright: IWM

Contact

Simone  Herzog © Copyright: IWM

Name

Simone Herzog

Group Leader Process Technology

Phone

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+49 241 80 96514

Email

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Motivation

Ceramic O2-conducting membranes can selectively separate oxygen from the air at temperatures above 750 °C and an adjacent oxygen partial pressure gradient. If this oxygen is used as combustion gas, e.g. in an oxyfuel combustion, it is possible to separate and store the resulting CO2 or convert it chemically. For the industrial implementation of this membrane technology, a reliable, gas-tight and high-temperature stable joining of ceramic membranes to metal components must be developed.

In previous projects, different joining methods for the ceramic Ba0.5Sr0.5Co0.8Fe0.2O3- (BSCF) have already been tested. Only the reactive brazing (RAB - Reactive Air Brazing) of BSCF using Ag-CuO braze alloys on the austenitic steel X15CrNiSi25-21 can potentially meet the high requirements. However, new phases and microcracks formed at the boundary layer of the ceramic during brazing, which deteriorate the mechanical properties.

Now, in the follow-up project, it is to be simulated how and why this reaction layer forms. The findings will be used to subsequently avoid or advantageously design the reaction layers by adapting the process.

Objectives

  • Development of a methodology for the quantitative prediction of damage in the diffusion layers of reactive brazed BSCF steel composites

Project contents

  • thermodynamic modelling of subsystems (BSCF+Cu, Lot+Co, oxide layer of steel, steel+Cu+Co) and description in a common database
  • microstructure simulation to understand phase formation
  • micromechanical simulation to model the micro residual stress and macroscopic joint stress and experimental determination of the necessary model parameters
  • experimental validation of the microstructure and microstructure simulation on the basis of microsections and mechanical testing of joint samples

Project funding

  • German Research Society (DFG)

Project Partner

  • Access e.v.