Effect of thermal cycling on the mechanical properties of 350-grade maraging steel

Viswanathan, U.K.; Kishore, R.; Asundi, M.K.

doi:10.1007/bf02648963

Cited by 29 publications

(23 citation statements)

References 12 publications

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“…There has been extensive research on the topic of grain refinement through thermal treatments. [2][3][4][5][6][7][8][9][10] A common practice is thermal cycling, which was developed and first applied to Fe-12Ni-0.25Ti, 2) Fe-8Ni-2Mn-0.25Ti 3) and 9Ni 4) steels. Similar treatments were carried out independently on Fe-8Mn by Hwang and Morris 5) and Nasim and Wilson, 6) resulting in considerable grain refinement and improvement in toughness.…”

Section: Introductionmentioning

confidence: 99%

“…Similar treatments were carried out independently on Fe-8Mn by Hwang and Morris 5) and Nasim and Wilson, 6) resulting in considerable grain refinement and improvement in toughness. Attempts were also made to improve the mechanical properties of maraging steels such as 350-grade 7) and 300-grade 8) through thermal cycling. However, in the above work, [2][3][4][5][6][7][8] the toughness properties were improved due to the combined contribution of the retained/reverted austenite and grain refinement, usually at the expense of strength properties.…”

Section: Introductionmentioning

confidence: 99%

“…Attempts were also made to improve the mechanical properties of maraging steels such as 350-grade 7) and 300-grade 8) through thermal cycling. However, in the above work, [2][3][4][5][6][7][8] the toughness properties were improved due to the combined contribution of the retained/reverted austenite and grain refinement, usually at the expense of strength properties. In a recent work on a 250-grade maraging steel, the prior austenite grain was refined to about 6 mm after thermal cycling with no formation of reverted austenite.…”

Section: Introductionmentioning

confidence: 99%

“…An earlier work on 18Ni grade-250 and grade-300 maraging steels also reported that thermal cycling could refine the prior austenite grain size. 11) It should be noted that when maraging steels, i.e., martensitic precipitation hardening steels were studied, [7][8][9][10] attempts on grain refinement was through rapid austenitisation procedures, whereas studies on other alloys employed intercritical annealing in their thermal treatments. [2][3][4][5][6]11) In the latter cases, even when tempering treatments were included, 3,4) the purpose was to introduce thermally stable austenite but not to achieve precipitation hardening.…”

Section: Introductionmentioning

confidence: 99%

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Improving Toughness of PH13-8 Stainless Steel through Intercritical Annealing

et al. 2003

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An intercritical annealing step was introduced in the treatment of a PH13-8 stainless steel to improve the toughness of the alloy in aged condition. Four different treatment cycles, i.e. austenitisation (Q-treatment) and intercritical anneal (L-treatment), LQ, 2B (QLQL) and 2K (LQLQ) were carried out before aging treatment at 510°C for 4 h (the commercial H950 treatment). Optical and scanning electron microscopies, and Xray diffraction analysis were employed to study the microstructures of the alloys after different heat treatments. Hardness and Charpy impact strength of the samples were measured.Results show that significant grain refinement was observed after 2K and 2B treatment, but not after QL and LQ treatments. Such refinement of prior austenite grain did not lead to significant increase of hardness either before or after ageing. The Charpy impact strength of the alloy in aged condition was improved after the four pre-ageing treatments. The formation of a 'dual-phase' martensitic structure through intercritical annealing is thought to make the main contribution to the better toughness obtained, with beneficial effects also from grain refinement. All the four treatments offer better combined properties than the commercial treatment, whereas QL and LQ treatments may be cost-competitive. Relationships among heat treatment, microstructure and mechanical properties are discussed.KEY WORDS: stainless steel; toughness; grain refinement; intercritical annealing; heat treatment.Such grain refinement increased the strength of the alloy at room temperature, and a significant increase in ultimate tensile strength was observed at elevated temperatures. Recently Guo et al. reported that introducing an intercritical annealing step before the solution treatment of AerMet 100 (Fe-13.4Co-11.1Ni-3.1Cr-1.2Mo-0.23C in wt%), a high strength lath martensitic steel, may result in fine effective grain size.11) It should be noted that when maraging steels, i.e., martensitic precipitation hardening steels were studied, [7][8][9][10] attempts on grain refinement was through rapid austenitisation procedures, whereas studies on other alloys employed intercritical annealing in their thermal treatments. [2][3][4][5][6]11) In the latter cases, even when tempering treatments were included, 3,4) the purpose was to introduce thermally stable austenite but not to achieve precipitation hardening. The grain size was retained through the tempering step.3,4) It is not yet clear how the introduction of intercritical annealing will affect the precipitation kinetics and mechanical properties of precipitation hardening steels.The aim of the current research was to refine the grain size of PH13-8 stainless steel through the introduction of intercritical annealing treatment. The influence of thermal treatment on grain size, mechanical properties of the alloy before and after ageing, and precipitation kinetics was studied. The relationships among heat treatment, microstructure, and mechanical properties are also discussed. Experimental Procedures Alloy ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improving Toughness of PH13-8 Stainless Steel through Intercritical Annealing

et al. 2003

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“…O sistema de endurecimento Co-Mo ocorre devido ao efeito sinérgico que ambos possuem de aumentar a dureza da martensita durante o envelhecimento. O endurecimento provocado pelo cobalto e pelo molibdênio é bem maior do que a soma do endurecimento provocado por cada um deles, separadamente [6]. Os números entre parênteses referem-se ao limite de escoamento dessas ligas em unidades "ksi" após o tratamento térmico de envelhecimento.…”

Section: Aços Maragingunclassified

ESTUDO DA ESTABILIDADE DA AUSTENITA REVERTIDA EM UM AÇO MARAGING 18%Ni GRAU 300

Abreu¹,

Neto²,

Santos³

et al. 2018

ABM Proceedings

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ResumoOs aços maraging apresentam baixo teor de carbono e possuem uma estrutura cristalina martensítica tetrágonal de corpo centrado (TCC). Estes aços oferecem uma combinação única de alta resistência mecânica e boa tenacidade à fratura. Nesse trabalho, foi realizado um estudo in situ de radiação síncrotron na busca de avaliar a estabilidade da austenita revertida no aço maraging 18%Ni grau 300. Um corpo de prova do aço em estudo com dimensões padronizadas foi solubilizado a 840°C por 1 hora e resfriada ao ar. Em seguida foi aquecida a uma taxa de 10°C/s até 630°C, mantendo-se então nesta temperatura pelo tempo de 12 minutos. Posteriormente a este tratamento, a amostra foi resfriada até a temperatura ambiente a taxa de 15°C/s. Em cada estágio de ciclo térmico foi realizada medidas de radiação síncrotron com comprimento de onda (λ = 1.0332 Å). As frações volumétricas das fases austenita revertida e martensita presentes em cada etapa do ciclo térmico foram calculadas utilizando o método de comparação direta e através da área integrada relativa aos picos das fases. A estabilidade mecânica da austenita revertida sob carga externa foi estudada usando radiação in situ síncrotron. Palavras-chave: Aços Maraging -Austenita revertida -Tratamento termomecânico. STUDY OF THE STABILITY AUSTENITE REVERSED IN A STEEL MARAGING18%Ni 300 DEGREE Abstract Maraging steels have low carbon and have a body-centered cubic martensitic (BCC) crystalline structure. These steels offer a unique combination of high mechanical strength and good fracture toughness. In this work, a study in situ synchrotron radiation in seeking to assess the stability of reversed austenite in maraging steel grade 18%Ni 300. A flat bar sample with standard dimensions was solution treated at 840°C for 1 h and cooled in air. Then heated at a rate of 10°C per second to 630°C, keeping this temperature for 12 minutes. Subsequent to this treatment the sample was cooled to room temperature at a rate of 15°C per second. Measurements of synchrotron radiation with a wavelength (λ = 1.0332 Å) were performed at each stage of the heating cycle. The volume fraction of martensite and austenite phases present in each stage of the thermal cycle were calculated using the method of direct comparison and through the integrated area of the peak for the phases. The mechanical stability of the reverted austenite under external load was studied using synchrotron radiation-situ.

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In Situ Observations of the Microstructural Evolution during Heat Treatment of a PH 13‐8 Mo Maraging Steel

et al. 2023

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The standard heat treatment of PH 13‐8 Mo maraging steels consists of solution annealing and subsequent aging. Herein, it is investigated how an additional intercritical annealing step prior to aging affects the microstructure, and, consequently, the mechanical properties of a PH 13‐8 Mo maraging steel. In situ techniques by means of high‐temperature electron backscatter diffraction and high‐temperature X‐ray diffraction are applied to study the microstructural changes during intercritical annealing and subsequent aging. In addition, high‐resolution investigation methods, such as transmission electron microscopy and atom probe tomography supplemented by transmission Kikuchi diffraction, are used for an in‐depth characterization of the microstructure. The results reveal that a diffusion‐controlled martensite to austenite transformation accompanied by partitioning of the substitutional atoms Cr, Ni, and Mo takes place during intercritical annealing. As a result of partitioning during intercritical annealing, an inhomogeneous distribution of Ni remains in the microstructure after the martensitic transformation. Consequently, the formation of reverted austenite is facilitated during subsequent aging due to existing Ni‐enriched zones in martensite. Since the fracture toughness is significantly enhanced compared to the standard heat treatment, it is suggested that this improvement is related to the increased phase fraction of reverted austenite.

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Effect of thermal cycling on the mechanical properties of 350-grade maraging steel

Cited by 29 publications

References 12 publications

Improving Toughness of PH13-8 Stainless Steel through Intercritical Annealing

Improving Toughness of PH13-8 Stainless Steel through Intercritical Annealing

ESTUDO DA ESTABILIDADE DA AUSTENITA REVERTIDA EM UM AÇO MARAGING 18%Ni GRAU 300

In Situ Observations of the Microstructural Evolution during Heat Treatment of a PH 13‐8 Mo Maraging Steel

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