Effect of post-treatments under hot isostatic pressure on microstructural characteristics of EBM-built Alloy 718
Artikel i vetenskaplig tidskrift, 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.

Hot isostatic pressing

Electron beam melting,

Alloy 718

Additive manufacturing,

gamma ''

Heat treatment

Författare

Sneha Goel

Högskolan Väst

Anumat Sittiho

University of Idaho

Indrajit Charit

University of Idaho

Uta Klement

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Shrikant Joshi

Högskolan Väst

Additive Manufacturing

2214-8604 (eISSN)

Vol. 28 727-737

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2019-07-15