Hot Isostatic Pressing as an Advanced Processing Route for Fabrication and Post-treatment of Metallic Parts

Dear Colleagues,

The hot isostatic pressing (HIP) process was developed in 1955, and since then, it has undergone a radical process of renewing and developing. It was first used for cladding alloys for nuclear power production purposes. Today, HIP has gained renewed interest especially with the affirmation of the powder metallurgy near-net-shape HIP (NNSHIP) manufacturing processes and of the practice of HIP post-treating additive manufactured (AM) parts. Tailored cycles can be applied to a wide number of materials to obtain fully dense medium to big size components starting from loose powders or to eliminate the most significant flaws inherent in AM parts. Further achievements in cycle optimization are studied to enhance the reliability and performance of components operating in highly demanding environments. The application of these techniques is highly appealing especially for materials which are difficult to forge and to machine.

Apart from the clear technical achievements provided by HIP, new solutions in terms of HIP industrial equipment and of tooling for the NNSHIP process are currently introduced in the market to improve the manufacturing readiness level (MRL) of such fabrication routes and to reduce their related cost. Another topic of increasing interest is the development of reliable simulation models that help to design the tooling in NNSHIP, thus reducing the buy-to-fly index of this process.

The proposed Special Issue of Materials aims at presenting the latest efforts spent on the abovementioned topics. Contributions are particularly invited from, but not limited to, those who are involved in:

(i) Developing tailored HIP cycles for materials typically adopted for additive manufacturing, in particular (but not limited to) nickel-based superalloys, TiAl, or titanium-based alloys;

(ii) Understanding of microstructure evolutions due to HIP, for instance, recrystallization, second phase dissolution or grain boundary stability and of their impact towards mechanical properties;

(iii) Studying the effects of the high pressure levels on phase transformations in materials or of the implementation of thermal heat treatments during or immediately after the HIP cycle;

(iv) Developing simulation models regarding the single or multiple steps of near-net-shape HIP process (i.e., capsule filling and/or densification and/or microstructural evolutions during the cooling stage);

(v) Assessing eventual residual defects and shape stability of components after HIP and studying potential solutions for them;

(vi) Studying the interactions and modifications which can be activated by elemental diffusion at the interface between the powders and the capsule used to contain them in NNSHIP.

Prof. Dr. Daniele Ugues
Dr. Emilio Bassini
Guest Editors

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