Effects of building orientation and heat treatment on fatigue behavior of selective laser melted 17-4 PH stainless steel

Yadollahi, Aref; Shamsaei, Nima; Thompson, Scott M.; Elwany, Alaa; Bian, Linkan

doi:10.1016/j.ijfatigue.2016.03.014

Cited by 489 publications

(299 citation statements)

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“…This implies that the stress concentration factor imposed by porosity on this specimen was the lowest. This conclusion is drawn from the theory of fatigue, which states that the majority of the fatigue life of a specimen lies in the crack initiation stage [12,13]. Figure 5 shows fractographs of specimen X-4, which was cycled at maximum stress of 486 MPa and fractured after 181,753 cycles.…”

Section: Figure 3: Semi-log S-n Diagram For X-build Direction Specimensmentioning

confidence: 96%

“…Surface roughness is not a concern of this paper, as it is based on the investigation of machined and polished SLM Ti6Al4V (ELI) fatigue specimens, thereby eliminating the negative effect of surface roughness on fatigue. Porosity arises from un-melted or semi-melted metal powder; the pores are normally oval-shaped and located between two consecutive layers during the SLM process [12]. Thus their major axis is always horizontal, which brings about anisotropy between horizontally and vertically built SLM parts.…”

Section: Sources Of Fatigue Failure In As-built Dmls Of Ti6al4v (Eli)mentioning

confidence: 99%

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High Cycle Fatigue Properties of as-Built Ti6al4v (Eli) Produced by Direct Metal Laser Sintering

Malefane

Preez

Maringa

2017

SAJIE

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The high cycle fatigue (HCF) properties of direct metal laser sintering (DMLS) of Ti6Al4V (ELI) in three mutually orthogonal build directions were investigated by cycling specimens under load control, in a tension-tension fatigue testing machine. Semi-log graphs of maximum stress (S) against life (N) of the specimens produced along the respective three build directions were plotted, and the displayed endurance limits compared. Optical and scanning electron microscopy were used to compare and analyse the crack initiation and propagation characteristics of the specimens. The influence of the build direction on the fatigue properties of the tested specimens is discussed here. OPSOMMINGDie hoësiklus vermoeidheidseienskappe van direkte metaallaser sintering van Ti6Al4V in drie onderlinge ortogonale bourigtings is ondersoek deur monsters te onderwerp aan beheerde sikliese ladings met behulp van ŉ trek-trek vermoeidheidstoetsmasjien. Semi-log grafieke van maksimum spanning teen leeftyd (S-N grafieke) is vir die monsters saamgestel, saam met die onderskeie bou rigtings. Sodoende kon die vermoeidheidslewe vergelyk word. Optiese-en skandeer elektronmikroskopie is gebruik om die kraakvorming en -voortplanting te vergelyk en te analiseer. Die invloed van die bourigting op die vermoeidheidseienskappe van die monsters is bespreek. INTRODUCTIONWork done by the Centre for Rapid Prototyping and Manufacturing (CRPM) of the Central University of Technology Free State on the manufacture of parts using direct metal laser sintering (DMLS) of Ti6Al4V (ELI) powder has thus far been based on the static mechanical properties of such DMLS parts that have been stress-relieved. These static mechanical properties were found to conform to the properties of standard wrought Ti6Al4V (ELI) [1,2]. However, for DMLS Ti6Al4V (ELI) parts that are expected to experience cyclic loading, there is uncertainty that they will last their full operational life. This is due to limited available fatigue life data for the DMLS-produced alloy.This study presents baseline data and analyses on as-built DMLS Ti6Al4V (ELI), as a precursor to studies of DMLS Ti6Al4V (ELI) that is heat treated in order to tailor its microstructure to give the best high cycle fatigue (HCF) properties possible.

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Section: Figure 3: Semi-log S-n Diagram For X-build Direction Specimensmentioning

confidence: 96%

Section: Sources Of Fatigue Failure In As-built Dmls Of Ti6al4v (Eli)mentioning

confidence: 99%

High Cycle Fatigue Properties of as-Built Ti6al4v (Eli) Produced by Direct Metal Laser Sintering

Malefane

Preez

Maringa

2017

SAJIE

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“…Referring to the work conducted by Yadollahi et al [66], the defects formed between layers due to lack-of-fusion in the vertical coupon used in Edwards 3 [62] would be more detrimental to crack initiation. This is due to the exposure of a larger area of the defect, than Edwards 1 and 2, which explains the difference in HCF life shown in Figure 6.…”

Section: Micro-mechanism Contributionmentioning

confidence: 99%

“…Despite the lack of understanding of the LCF effects in SLM Ti-6Al-4V, some work has been conducted on the LCF behaviour of other materials additively manufactured, such as Inconel alloy 718, where a build orientation dependence on strain amplitude in symmetric strain-controlled results was observed [75]. Further LCF analysis has been conducted on 17-4 PH stainless steel by using symmetric strain-controlled tests, which showed that crack initiation sites on the LCF fracture surface were smaller than those on the HCF fracture surface [66]. As identified in [66], the defect distance from the surface was more important than the actual defect size in LCF.…”

Section: Axial Fatigue Loadingmentioning

confidence: 99%

A Review of the As-Built SLM Ti-6Al-4V Mechanical Properties towards Achieving Fatigue Resistant Designs

Agius

Kourousis

Wallbrink

2018

Metals

171

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Ti-6Al-4V has been widely used in both the biomedical and aerospace industry, due to its high strength, corrosion resistance, high fracture toughness and light weight. Additive manufacturing (AM) is an attractive method of Ti-6Al-4V parts' fabrication, as it provides a low waste alternative for complex geometries. With continued progress being made in SLM technology, the influence of build layers, grain boundaries and defects can be combined to improve further the design process and allow the fabrication of components with improved static and fatigue strength in critical loading directions. To initiate this possibility, the mechanical properties, including monotonic, low and high cycle fatigue and fracture mechanical behaviour, of machined as-built SLM Ti-6Al-4V, have been critically reviewed in order to inform the research community. The corresponding crystallographic phases, defects and layer orientations have been analysed to determine the influence of these features on the mechanical behaviour. This review paper intends to enhance our understanding of how these features can be manipulated and utilised to improve the fatigue resistance of components fabricated from Ti-6Al-4V using the SLM technology.

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“…Other steels, e.g., M2 tool steel [96,[129][130][131] and 17-4 PH stainless steel [132][133][134][135][136] have also been reported.…”

Section: Materials Manufactured With Slmmentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

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Linköping 2018Cover image: A fracture surface of EBM IN718 after tensile test at room temperature.During the course of research underlying this thesis, Dunyong Deng was enrolled in Agora Materiae, a multidiciplinary doctoral program at Linköping University, Sweden. Printed by LiU-Tryck 2018 © Dunyong Deng AbstractAdditive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome.Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases γ ′ /γ ′′ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships.The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments.For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture.iii Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is "work-hardened" by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can m...

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Effects of building orientation and heat treatment on fatigue behavior of selective laser melted 17-4 PH stainless steel

Cited by 489 publications

References 18 publications

High Cycle Fatigue Properties of as-Built Ti6al4v (Eli) Produced by Direct Metal Laser Sintering

High Cycle Fatigue Properties of as-Built Ti6al4v (Eli) Produced by Direct Metal Laser Sintering

A Review of the As-Built SLM Ti-6Al-4V Mechanical Properties towards Achieving Fatigue Resistant Designs

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

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