Ultrahigh-strength low-alloy steels with enhanced fracture toughness

Malakondaiah, G.; Srinivas, M.; Rao, P. Rama

doi:10.1016/s0079-6425(97)00016-9

Cited by 87 publications

(41 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, previous TEM observations have revealed that, oil-quenched 300 M steel showed relatively lengthy martensitic laths in contrast to the isothermally transformed bainitic laths of the same material [36]. However, our findings differ from the mechanisms suggested by those previous studies, in which the martensite grain refining was attributed to partitioning of austenite grains by pre-formed bainitic ferrite [3,[11][12][13][14][15]37]. If such a mechanism were true in the current experiments, the steel would have shown lengthy bainitic ferrite laths or plates to partition the austenite grains.…”

Section: Hardening Mechanism In Austempering Treatmentcontrasting

confidence: 93%

See 1 more Smart Citation

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Luo

Kitchen

Abubakri

2017

Metals

View full text Add to dashboard Cite

Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 • C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed X-ray diffraction method has been employed to dissolve the bainitic/martensitic ferrite phase as two sub-phases of different tetragonal ratios, which provides quantitative analyses of the carbon partitioning between the resultant ferrites and the retained austenite. The results show that, a short-term austempering treatment was in the incubation period of the bainite transformation, which resulted in maximum hardness being equivalent to the oil-quenching treatment. The associated microstructure comprises fine carbide-free martensitic and bainitic ferrites of supersaturated carbon contents as well as carbon-rich retained austenite. In particular, the short-term austempering treatment helped prevent the formation of lengthy martensitic laths as those being found in the microstructure of oil-quenched sample. When the austempering time was increased from 20 to 80 min, progressive decrease of the hardness was associated with the evolution of the microstructure, including progressive coarsening of bainitic ferrite, carbide precipitating inside high-carbon bainitic ferrite and its subsequent decarbonisation.

show abstract

Section: Hardening Mechanism In Austempering Treatmentcontrasting

confidence: 93%

“…Such ferrite based microstructure enables ultrahigh strength properties, e.g., 2.5 GPa of compression strength and 2.3 GPa of ultimate tensile strength. However, such a process needs a very long salt bath time, and concern also arises from the low toughness property [5,6,11].…”

Section: Introductionmentioning

confidence: 99%

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Luo

Kitchen

Abubakri

2017

Metals

View full text Add to dashboard Cite

show abstract

“…Lower nickel-containing steels, such as UNS G43400 (SAE/AISI 4340), have interlath-retained austenite when quenched and tempered at temperatures up to 250°C (Malakondaiah, Srinivas, & Rama Rao, 1997). A tempering temperature in the 200°C-250°C range is considerably lower than recommended tempering temperatures for high-strength steels for O&G applications.…”

Section: Effect Of Nickel In Fracture Toughnessmentioning

confidence: 99%

“…Interlathretained austenite in UNS G434000 (SAE/AISI 4340) also increases fracture toughness (Zhirafar et al, 2007). Proposed mechanisms for the improved fracture toughness with retained austenite include promotion of crack branching, crack blunting due to plastic flow in retained austenite, prevention of interlath boundary carbide precipitation, and transformation-induced plasticity, where retained austenite transforms to martensite at the crack tip, relieving stress concentration (Malakondaiah et al, 1997;Narasimha Rao & Thomas, 1980).…”

Section: Effect Of Nickel In Fracture Toughnessmentioning

confidence: 99%

Sulfide stress cracking of nickel-containing low-alloy steels

et al. 2014

View full text Add to dashboard Cite

Low-alloy steels (LAS) are extensively used in oil and gas (O&G) production due to their good mechanical properties and low cost. Even though nickel improves mechanical properties and hardenability with low penalty on weldability, which is critical for large subsea components, nickel content cannot exceed 1-wt% when used in sour service applications. The ISO 15156-2 standard limits the nickel content in LAS on the assumption that nickel concentrations above 1-wt% negatively impact sulfide stress cracking (SSC) resistance. This restriction excludes a significant number of high-strength and high-toughness alloys, such as Ni-Cr-Mo (e.g., UNS G43200 and G43400), Ni-Mo (e.g., UNS G46200), and Ni-Cr-Mo-V grades, from sour service applications and can be used only if successfully qualified. However, the standard is based on controversial research conducted more than 40 years ago. Since then, researchers have suggested that it is the microstructure that determines SSC resistance, regardless of Ni content. This review summarizes the advantages and disadvantages of nickel-containing LAS in terms of strength, weldability, hardenability, potential weight savings, and cost reduction. Likewise, the state of knowledge on the effect of nickel on hydrogen absorption as well as SSC initiation and propagation kinetics is critically reviewed.

show abstract

“…Among these, the application of suitable coatings appears to be a promising method of corrosion control in terms of cost effectiveness and service life. DMR-1700 is a recently developed ultrahigh-strength low-alloy steel with improved mechanical properties compared with other aerospace-grade low-alloy steels [11]. However, its corrosion characteristics have not been investigated in detail, although some corrosion studies have been carried out [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Effect of environment on corrosion characteristics of newly developed DMR-1700 structural steel

Gurrappa

Malakondaiah

2008

Science and Technology of Advanced Materials

View full text Add to dashboard Cite

The corrosion resistance of any metallic material depends on the environment to which it is exposed. DMR-1700 steel is a material for structural applications that has been recently developed at Defence Metallurgical Research Laboratory by changing the chemistry of alloying elements. Therefore, a detailed understanding of its corrosion characteristics under different environmental conditions is essential. In the present paper, we report the results of a systematic corrosion study that was carried out on the new steel to determine the effect of the environment on the protective nature of the oxide scale that forms on its surface under different environmental conditions. Furthermore, the oxide scale as well as the resistance to pitting and crevice corrosion were studied in various environments. The surface morphologies of the corroded steels were observed under a scanning electron microscope (SEM) to determine the nature of the corrosion. On the basis of studies by different techniques, DMR-1700 steel is recommended for the manufacture of components used in various systems in conjunction with the application of an appropriate protective coating to improve its resistivity to corrosion.

show abstract

Ultrahigh-strength low-alloy steels with enhanced fracture toughness

Cited by 87 publications

References 33 publications

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Sulfide stress cracking of nickel-containing low-alloy steels

Effect of environment on corrosion characteristics of newly developed DMR-1700 structural steel

Contact Info

Product

Resources

About