Experimental studies on process-induced morphological characteristics of macro- and microstructures in laser consolidated alloys

Chen, Jianyin; Xue, Lijue; Wang, Sheng-Hui

doi:10.1007/s10853-011-5543-3

Cited by 37 publications

(14 citation statements)

References 24 publications

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“…These columnar grains have been observed in both SLM powder-bed [13] and blown-powder laser fabricated [14][15][16][17][18] materials. The results presented by Liu et al [15] are of particular interest as they show not only the columnar grains within the blown-powder laser fabricated material, but also fine grained regions formed due to the scan spacing.…”

Section: Grain Structure In Laser Fabricated Materialsmentioning

confidence: 85%

The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy

Carter

Martin

Withers

et al. 2014

Journal of Alloys and Compounds

623

200

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a b s t r a c tDuring the development of a processing route for the Selective Laser Melting (SLM) powder-bed fabrication of the nickel superalloy CM247LC it has been observed that the 'island' scan-strategy used as standard by the Concept Laser M2 SLM powder-bed system strongly influences the grain structure of the material.Optical and SEM micrographs are presented to show the observed grain structure in the SLM fabricated and Hot Isostatically Pressed (HIPped) material. The repeating pattern shown in the grain structure has been linked to the overlapping of the 'island' pattern used as standard in the Concept Laser M2 powderbed facility. It is suggested that the formation of this bi-modal grain structure can be linked to the heat transfer away from the solidifying melt pool. The concept of a 'band' heating effect across each 'island' rather than 'moving point' heating has been suggested and has been supported by Electron Back Scattered Diffraction (EBSD) evidence. For comparison an EBSD map from a sample formed using a simple 'back-and-forth' strategy has also been presented and reveals a dramatically different grain structure and crystallographic orientation.MicroCT evidence, supported by SEM microscopy, shows that in the as-fabricated material the bimodal structure caused by the 'island' scan-strategy translates directly into the macroscopic pattern for the regions of extensive weld cracking associated with the SLM fabrication of c 0 hardenable materials. Similar microCT data has shown that HIPping can effectively close the internal cracks to provide a retro-fix solution.

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Section: Grain Structure In Laser Fabricated Materialsmentioning

confidence: 85%

The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy

Carter

Martin

Withers

et al. 2014

Journal of Alloys and Compounds

623

200

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“…A variety of LMD machines and laser systems are being used for the fabrication of metals and alloys including Ti-6Al-4V, such as LEMS TM Nd:YAG, Trumpf HLD 3504 Yb:YAG and IPG with Yb fibre laser [67][68][69][70][71][72][73][74][75][76][77][78]. Figure 4 and Table 5 present the general working principle, working conditions and key machine/processing parameters.…”

Section: Laser Metal Deposition (Lmd)mentioning

confidence: 99%

An Overview of Densification, Microstructure and Mechanical Property of Additively Manufactured Ti-6Al-4V — Comparison among Selective Laser Melting, Electron Beam Melting, Laser Metal Deposition and Selective Laser Sintering, and with Conventional Powder

Yan¹,

Yu²

2015

Sintering Techniques of Materials

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“…The issue of cracking is typically not addressed as much of this research deals with the more easily processed materials of Inconel 718 [21][22][23] and Inconel 738 [23][24][25], which either have a lower γ′ fraction or the slower precipitating γ′′ phase, thus reducing the susceptibility for weld cracking.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to the grain structure, the γ′ structure of laser deposited material has been shown to be quite different to that of a conventionally formed material. Several authors have reported a limited precipitation of the γ′ phase due to the rapid cooling of the material following deposition [23,25,27] and as such will influence the heat treatment required to idealise the microstructure for functional use. The presence of residual stress in laser fabricated Ni-based superalloys poses a significant area of interest with studies being carried out into measurement [21,31] and modeling [32].…”

Section: Introductionmentioning

confidence: 99%

Laser Powder Bed Fabrication of Nickel-base Superalloys: Influence of Parameters; Characterisation, Quantification and Mitigation of Cracking

Carter¹,

Attallah²,

Reed³

2012

Superalloys 2012 (Twelfth International Symposium)

124

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The use of a selective laser melting (SLM) powder-bed method to manufacture Ni-based superalloys components provides an economic approach for low production run components that operate under a high-temperature and stress environment. A major concern with the SLM of precipitation hardenable Ni-based superalloys is their high susceptibility to cracking, which has been heavily documented in the field of welding. Weld cracking may occur either during processing (hot cracking, liquation cracking and ductility-dip cracking) or during the post weld heat-treatment stage (strain-age cracking). Due to the complex thermal history of SLM fabricated material there is the potential for all of these mechanisms to be active.In this investigation, cuboidal coupons of the Ni-based superalloy CM247LC were fabricated by the SLM of argon gas atomised powder. Parametric studies were performed to investigate the influence of the process parameters (laser scan speed, power and scan spacing) on the cracking density and morphology through conducting a stereological study of scanning electron microscope (SEM) micrographs. Further microstructural evidence is presented, illustrating the different crack morphologies observed as well as suggesting the responsible mechanisms. Finally a postfabrication Hot Isostatic Pressing (HIP) treatment was performed to investigate its utility in 'healing' the internal cracks, and providing a route to retro-fix the cracking problem in the heat treatment stage of production. The findings highlight the need for process models of the SLM method in order to understand the thermal history and the laser fabricated structures observed.

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Experimental studies on process-induced morphological characteristics of macro- and microstructures in laser consolidated alloys

Cited by 37 publications

References 24 publications

The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy

The influence of the laser scan strategy on grain structure and cracking behaviour in SLM powder-bed fabricated nickel superalloy

An Overview of Densification, Microstructure and Mechanical Property of Additively Manufactured Ti-6Al-4V — Comparison among Selective Laser Melting, Electron Beam Melting, Laser Metal Deposition and Selective Laser Sintering, and with Conventional Powder

Laser Powder Bed Fabrication of Nickel-base Superalloys: Influence of Parameters; Characterisation, Quantification and Mitigation of Cracking

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