Influence of the initial porosity on the hot isostatic pressing of components manufactured with additives


Markus Mirz © Copyright: IWM


Markus Mirz

Group Process Technology


+49 241 80 99543




Laser beam melting (LPBF) and electron beam melting (EPBF) are established additive manufacturing (AM) processes. They are based on the local melting of particles from a powder bed by means of a discrete radiation. In this process, components of high complexity with very low porosity can be produced. However, complete freedom from porosity cannot be achieved for process-related reasons. The residual porosity has a negative effect on the mechanical properties, especially pores have a strong influence on the fatigue strength of a component. One possibility to reduce the porosity is hot isostatic pressing (HIP) for post-compaction. However, the influence of different gas pores on the post-compaction capacity with HIP has not been clearly understood so far. A special influence on the HIP process could be the process atmosphere in form of the process gas. Depending on the gas with which the pores are filled, they either have an influence on the microstructure or the compression capacity. An understanding of the relationship between porosity, HIP and process atmosphere could lead to shorter process times through the targeted introduction of pores, as well as improved component reliability.

Complete understanding of the correlations between process gas in powder production, process atmosphere of AM processes, hot isostatic pressing, the resulting porosity, as well as the resulting material structure and mechanical properties under cyclic loading.

Project contents

  • Characterization of the starting powder
  • Investigation of the effect of different process atmospheres in AM processes on the chemical composition and microstructure
  • Determination of the limits of HIP post-compaction depending on the initial porosity and process atmosphere
  • Evaluation of the potential of HIP post-compaction to improve the mechanical properties of samples with different porosity and process atmospheres

Project Funding

  • DFG (German Research Foundation)
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