Effect of post-treatments under hot isostatic pressure on microstructural characteristics of EBM-built Alloy 718
Journal article, 2019

Electron beam melting (EBM) has emerged as an important additive manufacturing technique. In this study, Alloy 718 produced by EBM was investigated in as-built and post-treated conditions for microstructural characteristics and hardness. The post-treatments investigated were hot isostatic pressing (HIP) and combined HIP + heat treatment (HIP + HT) carried out as a single cycle inside the HIP vessel. Both the post-treatments resulted in significant decrease in defects inevitably present in the as-built material. The columnar grain structure of the as-built material was found to be maintained after post-treatment, with some sporadic localized grain coarsening noted. Although HIP led to complete dissolution of δ and γ′′ phase, stable NbC and TiN (occasionally present) particles were observed in the post-treated specimens. Significant precipitation of γ′′ phase was observed after HIP + HT, which was attributed to the two-step aging heat treatment carried out during HIP + HT. The presence of γ′′ phase or otherwise was correlated to the hardness of the material. While the HIP treatment resulted in drop in hardness, HIP + HT led to ‘recovery’ of the hardness to values exceeding those exhibited by the as-built material.

Electron beam melting,

gamma ''

Hot isostatic pressing

Additive manufacturing,

Alloy 718

Heat treatment


Sneha Goel

University West

Anumat Sittiho

University of Idaho

Indrajit Charit

University of Idaho

Uta Klement

Chalmers, Industrial and Materials Science, Materials and manufacture

Shrikant Joshi

University West

Additive Manufacturing

2214-8604 (eISSN)

Vol. 28 727-737

Driving Forces

Sustainable development

Subject Categories

Materials Engineering

Other Materials Engineering

Metallurgy and Metallic Materials

Areas of Advance


Materials Science



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