Thermal embrittlement in 18Ni cobalt free and 18Ni–8Co–5Mo maraging steels

Sinha, P. P.; Sivakumar, D.; Tharian, Thomas; Nagarajan, K. V.; Sarma, D. S.

doi:10.1179/026708396790122189

Cited by 3 publications

(6 citation statements)

References 7 publications

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“…Nes and Thomas [45] concluded that the TE results from the heterogeneous decomposition of supersaturated Fe -Ti -C solid solution obtained during high-temperature solution treatment. More recently Sinha et al [39] reported their detailed studies on TE in both Cobalt-bearing and Cobalt-free grades of 18 % Ni maraging steel. More recently Sinha et al [39] reported their detailed studies on TE in both Cobalt-bearing and Cobalt-free grades of 18 % Ni maraging steel.…”

Section: Thermal Embrittlement Of Maraging Steelsmentioning

confidence: 99%

“…Sinha et al [39] reported that no embrittlement was observed when the maraging steels were quenched from 1200°C to room temperature and subsequently re-heated rapidly to an intermediate temperature in the range 780 to 950°C. They attributed the non-occurrence of embrittlement when heat treated this way to the uniform precipitation of Ti(C, N) throughout the matrix on dislocations resulting from the martensite to austenite transformation.…”

Section: Heat Treatments To Refine the Pag And To Undo The Tementioning

confidence: 99%

“…The toughness could be improved by solution treatment at 1200°C followed by water quenching and cycling two times between 925°C and room temperature. The importance of the heating rate in the context of achieving grain refinement has been emphasized by Sinha et al [39]. J. Mat.…”

Section: Heat Treatments To Refine the Pag And To Undo The Tementioning

confidence: 99%

“…Sinha et al [39] could get grain refinement in both C18Ni1700 and T18Ni1700 by heating from room temperature to a temperature as low as 800°C in the austenitic phase field. Saul et al [36] and Maki et al [55] have reported that recrystallization in maraging steels is possible only when heating is done to temperatures above 900°C.…”

Section: Heat Treatments To Refine the Pag And To Undo The Tementioning

confidence: 99%

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Progress in understanding the metallurgy of 18% nickel maraging steels

Rao

2006

International Journal of Materials Research

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Progress in understanding the metallurgy of 18 % nickel maraging steelsMaraging steels based on iron -nickel martensite constitute a very important family of high-strength steels, which distinguishes itself by demonstrating an unparalleled combination of excellent fabricability and high strength and fracture toughness after heat treatment. Heat treatment of these steels has now been perfected to ensure consistently high levels of strength, ductility, and toughness in a variety of product shapes and sizes. Cobalt-free variants have been commercialized as part of efforts to save production costs. Further knowledge has been generated on 18 % nickel maraging steels regarding phases precipitating during aging, thermal embrittlement, thermal cycling and austenite reversion/retention and their effect on mechanical properties. The paper reviews the progress made over the last one and half decades.

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Section: Thermal Embrittlement Of Maraging Steelsmentioning

confidence: 99%

Section: Heat Treatments To Refine the Pag And To Undo The Tementioning

confidence: 99%

Section: Heat Treatments To Refine the Pag And To Undo The Tementioning

confidence: 99%

Section: Heat Treatments To Refine the Pag And To Undo The Tementioning

confidence: 99%

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Progress in understanding the metallurgy of 18% nickel maraging steels

Rao

2006

International Journal of Materials Research

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“…This level appears to be somewhat lower than required. There is evidence that Co level in this grade is peg- ged at 7.8 to 8.0 wt% [4][5][6]. The role of Co on the lowering of solid solubility of Mo in Fe-Ni martensitic matrix has been well established [1,7].…”

Section: Discussionmentioning

confidence: 99%

Significance of Alloying Element Levels in Realizing the Specified Tensile Properties in 18 Wt % Nickel Maraging Steel

Rao¹,

Sivasubramanian²

2011

MSA

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Among the various grades of commercially available 18 wt. % nickel maraging steels, the one with nominal 0.2% proof strength in the range 1700-1750 MPa is the most commonly used and is distinguished by an excellent combination of high strength and high fracture toughness. The main alloying elements are nickel, cobalt, molybdenum and titanium. The first three of these are present at relatively high concentrations in the chemical composition. The high cost of these metals leads to a high cost of production and this becomes a deterrent to extensive use of the steel. In the present study, an attempt was made to produce the steel by pegging the levels of these alloying elements in the lower half of the specified range. The objective was to save on the raw material cost, while still conforming to the specification. The steel so produced could not, however, attain the specified tensile properties after final heat treatment. The observed behavior is explained based on the role played by the different alloying elements in driving the precipitation hardening reaction

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Improvement of fracture toughness and tensile ductility of massive rings made of 18 % nickel maraging steel

Rao

Chatterjee²,

Sivasubramanian³

2012

HTM Journal of Heat Treatment and Materials

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Massive rings of 18% nickel maraging steel produced using the ring rolling process do not consistently attain high fracture toughness (KIc) and tensile ductility values. Due to large section sizes involved, it becomes difficult to suppress precipitation of carbonitride particles and prevent thermal embrittlement. The conventional heat treatment of solutioning at 820 °C followed by aging at 480 °C is not effective in undoing this embrittlement. Different multi-stage solution treatments were designed and tried out to improve the mechanical properties. A two-stage (950 °C + 820 °C)/three-stage (950 °C + 950 °C + 820 °C) solution treatment, depending on the section size, proved to be effective. This treatment leads to recrystallisation of the as-hot-worked microstructure and a fine grain size; it is believed that a delinking of grain boundaries and carbonitrides occurs simultaneously. The observed improvement of fracture toughness and tensile ductility can thus be explained.

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Thermal embrittlement in 18Ni cobalt free and 18Ni–8Co–5Mo maraging steels

Cited by 3 publications

References 7 publications

Progress in understanding the metallurgy of 18% nickel maraging steels

Progress in understanding the metallurgy of 18% nickel maraging steels

Significance of Alloying Element Levels in Realizing the Specified Tensile Properties in 18 Wt % Nickel Maraging Steel

Improvement of fracture toughness and tensile ductility of massive rings made of 18 % nickel maraging steel

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