Understanding the Role of Hot Isostatic Pressing Parameters on the Microstructural Evolution of Ti-6Al-4V and Inconel 718 Fabricated by Electron Beam Melting

Defects in electron beam melting (EBM) manufactured Alloy 718 are inevitable to some extent, and are of concern as they can degrade mechanical properties of the material. Therefore, EBM-manufactured Alloy 718 is typically subjected to post-treatment to improve the properties of the as-built material. Although hot isostatic pressing (HIPing) is usually employed to close the defects, it is widely known that HIPing cannot close open-to-surface defects. Therefore, in this work, a hypothesis is formulated that if the surface of the EBM-manufactured specimen is suitably coated to encapsulate the EBM-manufactured specimen, then HIPing can be effective in healing such surface-connected defects. The EBM-manufactured Alloy 718 specimens were coated by high-velocity air fuel (HVAF) spraying using Alloy 718 powder prior to HIPing to evaluate the above approach. X-ray computed tomography (XCT) analysis of the defects in the same coated sample before and after HIPing showed that some of the defects connected to the EBM specimen surface were effectively encapsulated by the coating, as they were closed after HIPing. However, some of these surface-connected defects were retained. The reason for such remnant defects is attributed to the presence of interconnected pathways between the ambient and the original as-built surface of the EBM specimen, as the specimens were not coated on all sides. These pathways were also exaggerated by the high surface roughness of the EBM material and could have provided an additional path for argon infiltration, apart from the uncoated sides, thereby hindering complete densification of the specimen during HIPing.

Download Full-text

Additive manufacturing titanium components with isotropic or graded properties by hybrid electron beam melting/hot isostatic pressing powder processing

Scientific Reports ◽

10.1038/s41598-019-40722-3 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 9

Author(s):

E. Hernández-Nava ◽

P. Mahoney ◽

C. J. Smith ◽

J. Donoghue ◽

I. Todd ◽

...

Keyword(s):

Electron Beam ◽

Additive Manufacturing ◽

Electron Beam Melting ◽

Powder Processing ◽

Hot Isostatic Pressing ◽

Isostatic Pressing ◽

Graded Properties ◽

Pressing Powder

Download Full-text

Role of Superficial Defects and Machining Depth in Tensile Properties of Electron Beam Melting (EBM) Made Inconel 718

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-05487-9 ◽

2021 ◽

Author(s):

Xiaoyu Zhao ◽

Amir Rashid ◽

Annika Strondl ◽

Christopher Hulme-Smith ◽

Niclas Stenberg ◽

...

Keyword(s):

Electron Beam ◽

Inconel 718 ◽

Electron Beam Melting ◽

Ultimate Tensile Stress ◽

Premature Failure ◽

Machined Parts ◽

Lower Yield Strength ◽

Low Performance ◽

Subsurface Defects

AbstractSince there is no report on the influence of machining depth on electron beam melting (EBM) parts, this paper investigated the role of superficial defects and machining depth in the performance of EBM made Inconel 718 (IN718) samples. Therefore, as-built EBM samples were analyzed against the shallow-machined (i.e., only removal of outer surfaces) and deep-machined (i.e., deep surface removal into the material) parts. It was shown that both as-built and shallow-machined samples had a drastically lower yield strength (970 ± 50 MPa), ultimate tensile stress (1200 ± 40 MPa), and ductility (28 ± 2%) compared to the deep-machined samples. This was since premature failure occurred due to various superficial defects. The superficial defects appeared in two levels, as (1) notches and pores on the surface and (2) irregular pores and cracks within the subsurface. Since the latter occurred down to 2 mm underneath the surface, shallow machining only exposed the subsurface defects to outer surfaces. Thus, the shallow-machined parts achieved only 68% and 8% of UTS and elongation of the deep-machined parts, respectively. This low performance occurred to be comparable to the as-built parts, which failed prematurely due to the high fraction surface voids and notches as well as the subsurface defects.

Download Full-text

The Effectiveness of Hot Isostatic Pressing for Closing Porosity in Titanium Parts Manufactured by Selective Electron Beam Melting

Metallurgical and Materials Transactions A ◽

10.1007/s11661-016-3429-3 ◽

2016 ◽

Vol 47 (5) ◽

pp. 1939-1946 ◽

Cited By ~ 103

Author(s):

Samuel Tammas-Williams ◽

Philip J. Withers ◽

Iain Todd ◽

Philip B. Prangnell

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Hot Isostatic Pressing ◽

Isostatic Pressing ◽

Selective Electron Beam Melting

Download Full-text

Effect of Hot Isostatic Pressing on Microstructures and Mechanical Properties of Ti6Al4V Fabricated by Electron Beam Melting

Metals ◽

10.3390/met10050593 ◽

2020 ◽

Vol 10 (5) ◽

pp. 593

Author(s):

Changyong Liu ◽

Zhuokeng Mai ◽

Deng Yan ◽

Mingguang Jiang ◽

Yuhong Dai ◽

...

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Grain Size ◽

Electron Beam ◽

Electron Beam Melting ◽

Hot Isostatic Pressing ◽

Phase Ratio ◽

Lamellar Thickness ◽

Isostatic Pressing ◽

Β Phase

This study investigated the effects of hot isostatic pressing (HIP) on the microstructures and mechanical properties of Ti6Al4V fabricated by electron beam melting (EBM). The differences of surface morphologies, internal defects, relative density, microstructures, textures, mechanical properties and tensile fracture between the as-built and HIPed samples were observed using various characterization methods including optical metallography microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) and tensile tests. It was found that the main effects of HIP on microstructures include—the increase of average grain size from 7.96 ± 1.21 μm to 11.34 ± 1.89 μm, the increase of α lamellar thickness from 0.71 ± 0.15 μm to 2.49 ± 1.29 μm and the increase of β phase ratio from 4.7% to 10.5% in terms of area fraction on the transversal section. The combinatorial effects including densification, increase of grain size, α lamellar thickness, β phase ratio, reduction of dislocation density and transformation of dislocation patterns contributed to the improvement of elongation and ductility of EBM-fabricated Ti6Al4V. Meanwhile, these effects also resulted in a slight reduction of the yield strength and UTS mainly due to the coarsening effect of HIP.

Download Full-text

Effect of HIPping (Hot Isostatic Pressing) on electron beam melting Ti6Al4V parts after machining

10.1063/1.4963616 ◽

2016 ◽

Cited By ~ 3

Author(s):

Adrien Dolimont ◽

Sebastien Michotte ◽

Edouard Rivière-Lorphèvre ◽

François Ducobu ◽

Charlotte de Formanoir ◽

...

Keyword(s):

Electron Beam ◽

Electron Beam Melting ◽

Hot Isostatic Pressing ◽

Isostatic Pressing

Download Full-text

ВПЛИВ ТЕХНОЛОГІЙ ПІДВЕДЕННЯ ЕНЕРГІЇ ПРИ 3D-ПРИНТИНГУ НА СТРУКТУРУ ТА ВЛАСТИВОСТІ ДЕТАЛЕЙ ЗІ СПЛАВУ Ti-6Al-4V

Aerospace technic and technology ◽

10.32620/aktt.2018.8.13 ◽

2018 ◽

pp. 86-90

Author(s):

Алексей Александрович Педаш ◽

Владимир Валериевич Клочихин ◽

Тамара Александровна Митина ◽

Валерий Григорьевич Шило

Keyword(s):

Mechanical Properties ◽

Electron Beam ◽

Selective Laser Melting ◽

Electron Beam Melting ◽

Melt Inclusions ◽

Hot Isostatic Pressing ◽

Alpha Phase ◽

Laser Melting ◽

Isostatic Pressing ◽

The Impact

The composition, structure and mechanical properties of samples obtained from the titanium alloy Ti-6Al-4V, by selective laser melting and electron beam melting processes regarding production of responsible aviation parts were carrying-out at present article.A comparative study of macro- and microstructure, mechanical properties has been carried out after inherent of Ti-6Al-4V heat treatment with or without prior hot isostatic pressing.It was established that the advent in specimens fractures and microstructure pores and non-melt inclusions of a granules condition obligatory hot isostatic pressing of a responsible parts when this kinds of defects significantly releases and correspondingly best complex of mechanical properties are obtained.The powders from titanium Ti-6Al-4V alloy were produce by inert gas (argon) spraying process and had a different particle sizing distribution: 20-50 microns for selective laser melting and 45-105 microns for electron beam melting.The microstructure of the specimens prepared using the studied production processes features an elongated lamellar alpha phase in the transformated epitaxially grown beta-matrix and is typical for Ti-6Al-4V alloy in a heat-treated condition.It has been noted that the lamellar alpha phase in the structure of the studied specimens after hot isostatic pressing is distinguished by larger sizes in width as compared to the specimens prior to hot isostatic pressing processing.Mechanical properties of the specimens produced by selective laser melting or electron beam melting processes meet the specification requirements. Hot isostatic pressing processing results in a remarkable improvement of the impact strength. Authors should be pointed out that application of additive technologies in the manufacture of aerospace parts requires extensive research&development works, and testing efforts to confirm repeatability of alloy characteristics. A mandatory procedure of the production process and material approval shall be conducted to ensure compliance with aircraft flight safety standards and regulations.

Download Full-text