Surface pick-up of argon during hot isostatic pressing of material built by laser powder bed fusion

Abstract This paper reports the effect of Hot Isostatic Pressing (HIPing) on the porosity, microstructure and mechanical properties of Laser Powder Bed Fusion (LPBF) IN625 structures built at a higher layer thickness of 100 µm. It is observed that the process-induced pores/voids of volume fraction (Vf) 0.43% in as-built IN625 structures are reduced significantly to ~ 0.01% after HIPing treatment. The microstructure is changed from fine columnar dendrites to coarse equiaxed dendrites. The microstructural analysis of as-built structures reveals the presence of cellular/ dendritic growth along with elemental segregation of Nb, Si and C and precipitation of Nb-rich carbides. Whereas, coarse recrystallized microstructure along with elemental segregation of Si and precipitation of Nb, Mo and Cr rich carbides are observed in Hot Isostatic Pressed (HIPed) samples. HIPed structures exhibit lower tensile s trength, higher ductility, and lower anisotropy as compared to LPBF built structures. There is a reduction in the Vickers micro-hardness of IN625 samples after HIPing and the values are observed to be similar to their conventional counterparts. Further, an increase in the energy storage capacity of the material is observed after HIPing treatment through Automated Ball Indentation (ABI®) studies. The study paves a way to develop ~100% dense, defect-free and isotropic engineering components using LPBF.

Download Full-text

Structure and Properties of Ti/Ti64 Graded Material Manufactured by Laser Powder Bed Fusion

Materials ◽

10.3390/ma14206140 ◽

2021 ◽

Vol 14 (20) ◽

pp. 6140

Author(s):

Evgenii Borisov ◽

Igor Polozov ◽

Kirill Starikov ◽

Anatoly Popovich ◽

Vadim Sufiiarov

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Additive Manufacturing ◽

Hot Isostatic Pressing ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Isostatic Pressing ◽

Graded Material ◽

Single Part

Multimaterial additive manufacturing is an attractive way of producing parts with improved functional properties by combining materials with different properties within a single part. Pure Ti provides a high ductility and an improved corrosion resistance, while the Ti64 alloy has a higher strength. The combination of these alloys within a single part using additive manufacturing can be used to produce advanced multimaterial components. This work explores the multimaterial Laser Powder Bed Fusion (L-PBF) of Ti/Ti64 graded material. The microstructure and mechanical properties of Ti/Ti64-graded samples fabricated by L-PBF with different geometries of the graded zones, as well as different effects of heat treatment and hot isostatic pressing on the microstructure of the bimetallic Ti/Ti64 samples, were investigated. The transition zone microstructure has a distinct character and does not undergo significant changes during heat treatment and hot isostatic pressing. The tensile tests of Ti/Ti64 samples showed that when the Ti64 zones were located along the sample, the ratio of cross-sections has a greater influence on the mechanical properties than their shape and location. The presented results of the investigation of the graded Ti/Ti64 samples allow tailoring properties for the possible applications of multimaterial parts.

Download Full-text

Fatigue crack growth in Ti-6Al-4V specimens produced by Laser Powder Bed Fusion and submitted to Hot Isostatic Pressing

Theoretical and Applied Fracture Mechanics ◽

10.1016/j.tafmec.2021.103231 ◽

2022 ◽

pp. 103231

Author(s):

J.S. Jesus ◽

L.P. Borrego ◽

J.A.M. Ferreira ◽

J.D. Costa ◽

A.C. Batista ◽

...

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Hot Isostatic Pressing ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed ◽

Isostatic Pressing

Download Full-text

Hot Isostatic Pressing of Aluminum–Silicon Alloys Fabricated by Laser Powder-Bed Fusion

Technologies ◽

10.3390/technologies8030048 ◽

2020 ◽

Vol 8 (3) ◽

pp. 48

Author(s):

Stephan Hafenstein ◽

Leonhard Hitzler ◽

Enes Sert ◽

Andreas Öchsner ◽

Markus Merkel ◽

...

Keyword(s):

Heat Treatment ◽

Supersaturated Solid Solution ◽

Hot Isostatic Pressing ◽

Powder Bed Fusion ◽

Solution Annealing ◽

Laser Powder Bed Fusion ◽

Sand Cast ◽

Powder Bed ◽

Isostatic Pressing ◽

Direct Aging

Hot isostatic pressing can be utilized to reduce the anisotropic mechanical properties of Al–Si–Mg alloys fabricated by laser powder-bed fusion (L-PBF). The implementation of post processing densification processes can open up new fields of application by meeting high quality requirements defined by aircraft and automotive industries. A gas pressure of 75 MPa during hot isostatic pressing lowers the critical cooling rate required to achieve a supersaturated solid solution. Direct aging uses this pressure related effect during heat treatment in modern hot isostatic presses, which offer advanced cooling capabilities, thereby avoiding the necessity of a separate solution annealing step for Al–Si–Mg cast alloys. Hot isostatic pressing, followed by rapid quenching, was applied to both sand cast as well as laser powder-bed fused Al–Si–Mg aluminum alloys. It was shown that the critical cooling rate required to achieve a supersaturated solid solution is significantly higher for additively manufactured, age-hardenable aluminum alloys than it is for comparable sand cast material. The application of hot isostatic pressing can be combined with heat treatment, consisting of solution annealing, quenching and direct aging, in order to achieve both a dense material with a small number of preferred locations for the initiation of fatigue cracks and a high material strength.

Download Full-text