# A Porosity Closure Model Under Hot Isostatic Pressing of an IN718 Alloy Manufactured by Powder Bed Fusion

## TL;DR

This paper develops a model to predict how porosity in 3D-printed IN718 alloy parts closes during hot isostatic pressing, improving manufacturing efficiency.

## Contribution

A novel porosity closure model for HIP of PBF-manufactured IN718 alloy is proposed and experimentally validated.

## Key findings

- A porosity closure model was established using logarithmic strain and volume compressible material equations.
- The HIP diagram for PBF-manufactured IN718 was constructed and validated with experiments.
- HIP effectively increased the relative density of components with different initial densities.

## Abstract

The low productivity and high cost of additive manufacturing techniques, such as powder bed fusion (PBF), limits its wide application in industry. A combined approach of hot isostatic pressing (HIP) and PBF was an effective means to solve this limitation. Nevertheless, there is currently a lack of a porosity closure model to design and optimize the HIP process parameters of PBF-manufactured components. The porosity closure condition of the PBF-manufactured component is deduced based on the additivity of logarithmic strain and the plastic equation of volume compressible material, and then a porosity closure model considering temperature and pressure is established and verified by molecular dynamics simulation. Subsequently, a HIP diagram of the PBF-manufactured IN718 is constructed. Four different initial relative densities of 0.956, 0.970, 0.984, and 0.996 of IN718 components are introduced by increasing the scanning speed of PBF. HIP post-treatment experiments of different relative density components are performed. The accuracy of the HIP diagram is verified by the relative density test and microstructure observation.