Thermal stabilization of additively manufactured superalloys through defect engineering and precipitate interactions

Munther, Michael; Rowe, Russell A.; Sharma, Montu; Hackel, Lloyd A.; Davami, Keivan

doi:10.1016/j.msea.2020.140119

Cited by 14 publications

(5 citation statements)

References 50 publications

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“…During the laser peening process, grain modifications occur at the surface and just beneath the surface of the material. In addition, the laser peening process and the induced dislocations encourage the formation of the subgrains [38]. Repeated pressure waves, due to multiple cycles of laser peening, lead to the formation of numerous shear bands, which act to promote the division of sub-grains into fine grains achieving further refinement of the surface grains [16,17].…”

Section: Resultsmentioning

confidence: 99%

Multi-cycling nanoindentation in additively manufactured Inconel 625 before and after laser peening

Tajyar¹,

Brooks²,

Vaseghi³

et al. 2022

Surf. Topogr.: Metrol. Prop.

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In this research, a room temperature multicycle nanoindentation technique was implemented to evaluate the effects of the laser peening (LP) process on the surface mechanical behavior of additively manufactured (AM) Inconel 625. Repetitive deformation was introduced by loading-unloading during an instrumented nanoindentation test on the as-built (No LP), 1-layer, and 4-layer laser peened (1LP and 4LP) conditions. It was observed that laser-peened specimens had a significantly higher resistance to penetration of the indenter and lower permanent deformation. This is attributed to the pre-existing dislocation density induced by LP in the material which affects the dislocation interactions during the cyclic indentation. Moreover, high levels of compressive stresses, which are greater in the 4LP specimen than the 1LP specimen, lead to more effective improvement of surface fatigue properties. The transition of the material response from elastic-plastic to almost purely elastic in 4LP specimens was initiated much earlier than it did in the No LP, and 1LP specimens. In addition to the surface fatigue properties, hardness and elastic modulus were also evaluated and compared.

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Section: Resultsmentioning

confidence: 99%

Multi-cycling nanoindentation in additively manufactured Inconel 625 before and after laser peening

Tajyar¹,

Brooks²,

Vaseghi³

et al. 2022

Surf. Topogr.: Metrol. Prop.

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“…This treatment supports the bene t of a unique process involving application of layers of laser peening using high energy with large footprint spots combined with interspersed cyclic annealing. LP + TME has already been shown to provide fatigue strength bene ts on additive manufactured nickel-based superalloy [19,20] and other alloys [21]. For these reasons, high energy LP + TME on single crystal CMSX-4® superalloy for turbine blade root application is of interest in the present work.…”

Section: Introductionmentioning

confidence: 91%

Effects of high energy laser peening followed by pre-hot corrosion on stress relaxation, microhardness and fatigue life and strength of single crystal nickel CMSX-4® superalloy

Morar

Holtham

Hackel

et al. 2023

Preprint

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This study investigated the stress relaxation and fatigue life and strength of laser peened single crystal nickel superalloy specimens compared to un-peened and shot peened specimens following hot corrosion exposure and then fatigue testing. The specimens were treated by conventional laser peening and a new cyclic laser peening plus thermal microstructure engineering process. The latter treatment supports the benefit of a unique process involving application of layers of laser peening using high energy with large footprint spots combined with interspersed cyclic annealing. Stress measurements by slitting showed the plastic penetration depth of laser peening exceeded shot peening by a factor of 24. Un-peened and peened specimens were exposed to sulphate corrosives at 700°C for 300 hours and then fatigue tested. Tests of five non-laser peened specimens all failed in low cycle fatigue regime whereas three identically tested laser peened specimens all achieved multi-million-cycle runout without failure, indicating fully consistent large benefit for life by laser peening. Additional tests also showed fatigue strength improvement of 2:1 by laser peening. Residual stress measurements post hot-corrosion exposure and fatigue testing showed notable 5 mm depth retention of residual eigenstress in a laser peened specimen.

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“…Thus, the initiative has been taken in the creation of modified LP treatments which include a heat treatment phase to maintain mechanical property improvements. Laser peening + thermal microstructure engineering (LP + TME) is one such method which incorporates annealing stages between layers of LP [46,47]. Recently, Munther et al reported that LP+TME implemented on additively manufactured Inconel 718 yielded 58% higher compressive residual stresses following a 350 h exposure to 600 • C (0.5 T m of Inconel 718) than a sample treated with LP [46].…”

Section: Microhardness Distribution Following Lpmentioning

confidence: 99%

“…Laser peening + thermal microstructure engineering (LP + TME) is one such method which incorporates annealing stages between layers of LP [46,47]. Recently, Munther et al reported that LP+TME implemented on additively manufactured Inconel 718 yielded 58% higher compressive residual stresses following a 350 h exposure to 600 • C (0.5 T m of Inconel 718) than a sample treated with LP [46]. As previously discussed, residual stresses induced by LP typically relax at high temperatures but in LP+TME, relaxation is greatly mitigated.…”

Section: Microhardness Distribution Following Lpmentioning

confidence: 99%

A Review of Laser Peening Methods for Single Crystal Ni-Based Superalloys

Holtham

Davami

2022

Metals

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Single crystal Ni-based superalloys are often used to create gas turbine engine blades for their high strength under intense thermo-mechanical loading. Though they are remarkably capable under these conditions, a particular class of premature failure mechanisms known as surface-initiated damage mechanisms can lead to the early fracture of an otherwise healthy blade. This review paper discusses the current progress of post-processing techniques that can greatly mitigate the potency of surface-initiated damage mechanisms. In particular, laser peening (LP) is of significant interest due to the relatively low amount of cold work it induces, greater depth of compressive residual stresses than other cold working methods, ability to accommodate complex part geometries, and the minuscule effect it has on surface roughness. The residual stresses imparted by LP can greatly hinder crack growth and consequently allow for enhanced fatigue life. Given that turbine blades (constructed with single crystal Ni-based superalloys) are prone to fail by these mechanisms, LP could be a worthy choice for increasing their service lives. For this reason, initiative has been taken to better understand the mechanical and microstructural modifications imparted by LP on single crystal Ni-based superalloys and a summary of these investigations are presented in this review. Results from several works show that this class of alloy responds well to LP treatment with improvements such as ~30–50% increase in microhardness, 72% increase in low cycle fatigue life, and elevated resistance to hot corrosion. The primary objective of this review is to provide insight into current state-of-the-art LP techniques and summarize the findings of numerous works which have utilized LP for increasing the service lives of single crystal Ni-based superalloy components.

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Thermal stabilization of additively manufactured superalloys through defect engineering and precipitate interactions

Cited by 14 publications

References 50 publications

Multi-cycling nanoindentation in additively manufactured Inconel 625 before and after laser peening

Multi-cycling nanoindentation in additively manufactured Inconel 625 before and after laser peening

Effects of high energy laser peening followed by pre-hot corrosion on stress relaxation, microhardness and fatigue life and strength of single crystal nickel CMSX-4® superalloy

A Review of Laser Peening Methods for Single Crystal Ni-Based Superalloys

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