Boro-Austempering Treatment of High-Strength Bainitic Steels

Oliveira, Paulo Gonçalves de; Mariani, Fábio; Casteletti, Luíz Carlos; Filho, André Itman; Neto, Amadeu Lombardi; Totten, George E.

doi:10.1007/s11665-020-04590-7

Cited by 12 publications

(12 citation statements)

References 23 publications

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“…During Q&P, once steel is austenitized, it is quenched at a temperature between martensite start temperature (Ms) and Mf (martensite finish temperature) and then soaked at the so-called partition temperature (PT). At PT carbon diffuses from martensite to retained austenite favoring its retention at room temperature and enhancing strength and ductility [21].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Intercritical Annealing and Austempering on the Microstructure and Mechanical Properties of a High Silicon Manganese Steel

Franceschi

Pezzato

Gennari

et al. 2020

Metals

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High Silicon Austempered steels (AHSS) are materials of great interest due to their excellent combination of high strength, ductility, toughness, and limited costs. These steel grades are characterized by a microstructure consisting of ferrite and bainite, accompanied by a high quantity retained austenite (RA). The aim of this study is to analyze the effect of an innovative heat treatment, consisting of intercritical annealing at 780 °C and austempering at 400 °C for 30 min, on the microstructure and mechanical properties of a novel high silicon steel (0.43C-3.26Si-2.72Mn wt.%). The microstructure was characterized by optical and electron microscopy and XRD analysis. Hardness and tensile tests were performed. A multiphase ferritic-martensitic microstructure was obtained. A hardness of 426 HV and a tensile strength of 1650 MPa were measured, with an elongation of 4.5%. The results were compared with those ones obtained with annealing and Q&T treatments.

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Section: Introductionmentioning

confidence: 99%

“…Oliveira et al [21], analyzing the behavior of a MnSi steel after austempering and Q&P, observed that in the first case a microstructure consisting in a mixture of plate and granular bainite, martensite, and retained austenite is present. After Q&P a martensite matrix with bainitic islands and austenite films/blocks is instead formed.…”

Section: Introductionmentioning

confidence: 99%

Effect of Intercritical Annealing and Austempering on the Microstructure and Mechanical Properties of a High Silicon Manganese Steel

Franceschi

Pezzato

Gennari

et al. 2020

Metals

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“…However, few studies on boro-austempering treatment of high-strength bainitic steels have been reported. [27] Oliveira et al [27] reported that the boro-austempering treatment was a promising alternative to increase the wear resistance of AHSS. However, the effect of boriding time in boro-austempering treatment on microstructure and properties are not investigated and it is not clear whether the thickness of borided layer is affected by bainitic transformation.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Properties of a Medium‐Carbon High‐Strength Bainitic Steel Treated by Boro‐Austempering Treatment

Liu

Wang

Pan

et al. 2020

steel research int.

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The microstructure and properties of a medium‐carbon high‐strength bainitic steel treated by integrated technology of austempering and boriding treatments (boro‐austempering) are investigated by metallographic method, electrochemical impedance spectroscopy, and so on. The results show that the carbide‐free bainite of substrate and the borided layers on the surface are successfully obtained by integrated boro‐austempering treatment. The hardness of surface is up to 2.5–3.0 times that of substrate and the surface corrosion resistance is significantly enhanced by boro‐austempering treatment, proving that boro‐austempering treatment is an effective method for increasing corrosion resistance and hardness of high‐strength bainitic steels. The present study provides a new and effective processing technology for the production of medium‐carbon high‐strength steels with better corrosion resistance and higher hardness.

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“…After the austenitizing step, the material is cooled to the austempering temperature (AT) that is between bainite start (Bs) and martensite start (Ms). Once the selected AT is reached, the material is isothermally held and then cooled to room temperature [ 4 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Different Austempering Heat Treatments on Corrosion Properties of High Silicon Steel

et al. 2021

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A novel high silicon austempered (AHS) steel has been studied in this work. The effect of different austenitizing temperatures, in full austenitic and biphasic regime, on the final microstructure was investigated. Specimens were austenitized at 780 °C, 830 °C, 850 °C and 900 °C for 30 min and held isothermally at 350 °C for 30 min. A second heat treatment route was performed which consisted of austenitizing at 900 °C for 30 min and austempering at 300 °C, 350 °C and 400 °C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been used to evaluate the microstructural evolution. These techniques revealed that the microstructures were composed of carbide-free bainite, ferrite, martensite and retained austenite (RA) in different volume fractions (Vγ). An aqueous borate buffer solution with 0.3 M H3BO3 and 0.075 M Na2B4O7∂10H2O (pH = 8.4) was used for corrosion tests in order to evaluate the influence of the different volume fractions of retained austenite on the corrosion properties of the specimens. The results showed that when increasing the austenitization temperatures, the volume fractions of retained austenite reached a maximum value at 850 °C, and decrease at higher temperatures. The corrosion properties were investigated after 30 min and 24 h immersion by means of potentiodynamic polarization (after 30 min) and electrochemical impedance spectroscopy (after both 30 min and 24 h) tests. The corrosion resistance of the samples increased with increases in the volume fraction of retained austenite due to lower amounts of residual stresses.

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Boro-Austempering Treatment of High-Strength Bainitic Steels

Cited by 12 publications

References 23 publications

Effect of Intercritical Annealing and Austempering on the Microstructure and Mechanical Properties of a High Silicon Manganese Steel

Effect of Intercritical Annealing and Austempering on the Microstructure and Mechanical Properties of a High Silicon Manganese Steel

Microstructure and Properties of a Medium‐Carbon High‐Strength Bainitic Steel Treated by Boro‐Austempering Treatment

Effect of Different Austempering Heat Treatments on Corrosion Properties of High Silicon Steel

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