Microstructural Features Affecting Tempering Behavior of 16Cr-5Ni Supermartensitic Steel

Sanctis, Massimo De; Lovicu, Gianfranco; Valentini, Renzo; Dimatteo, A.; Ishak, Randa; Migliaccio, U.; Montanari, Roberto; Pietrangeli, Emanuele

doi:10.1007/s11661-015-2811-x

Cited by 29 publications

(33 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[50] However, the fraction of austenite retained after quenching from austenitization was about 1 vol pct lower for the samples previously austenitized at 1323 K (1050°C) for 30.5 hours and is not considered to have a significant contribution to the much larger difference in austenite fraction obtained after the tempering experiments.…”

Section: B Influence Of Previous Austenitization Treatment On the Aumentioning

confidence: 89%

Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

Bojack

Zhao

Morris

et al. 2016

Metall Mater Trans A

View full text Add to dashboard Cite

The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dissolution during the second, higher temperature, stage. A better homogenization of the material causes an increase in the transformation temperatures for the martensite-to-austenite transformation and a lower retained austenite fraction with less variability after tempering. Furthermore, the martensite-to-austenite transformation was found to be incomplete at the target temperature of 1223 K (950°C), which is influenced by the previous austenitization treatment and the heating rate. The activation energy for martensite-to-austenite transformation was determined by a modified Kissinger equation to be approximately 400 and 500 kJ/mol for the first and the second stages of transformation, respectively. Both values are much higher than the activation energy found during isothermal treatment in a previous study and are believed to be effective activation energies comprising the activation energies of both mechanisms involved, i.e., nucleation and growth.

show abstract

Section: B Influence Of Previous Austenitization Treatment On the Aumentioning

confidence: 89%

Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

Bojack

Zhao

Morris

et al. 2016

Metall Mater Trans A

View full text Add to dashboard Cite

show abstract

“…As the tempering temperature increases, the volume fraction of reversed austenite increases and the consequent solute redistribution is no longer able to stabilize the γ phase on cooling. This aspect is believed to be critical for 13Cr-4Ni-(Mo) industrial heats, which are characterized by relatively low carbon and nickel contents as compared to other supermartensitic alloys [6]. Moreover, alloying with molybdenum (0.5%) reduces carbon diffusion towards reverted austenite islands, thus further limiting stabilization of reverted austenite and lowering kinetics for martensite recovery.…”

Section: Discussionmentioning

confidence: 99%

“…Tempering should maximize the recovery of the martensitic matrix and promote the retention of soft retained austenite at room temperature. Previous studies on the thermal behavior of low-carbon 13Cr-4Ni alloy [2] and 16Cr-5Ni-(Mo) [6] showed that the amount of retained austenite increases with increasing reversion treatment temperature, exhibiting a peak typically in the range 620-640 • C. Above this range, it decreases with increasing temperatures, leading to the formation of virgin martensite upon cooling, with increasing hardness. It has been suggested that the stability of reversed austenite initially increases because of the diffusion of nickel and other gamma-stabilizing elements from the martensitic matrix towards reverted austenite islands [7][8][9].…”

Section: Introductionmentioning

confidence: 97%

Study of 13Cr-4Ni-(Mo) (F6NM) Steel Grade Heat Treatment for Maximum Hardness Control in Industrial Heats

Sanctis

Lovicu²,

Buccioni³

et al. 2017

Metals

Self Cite

View full text Add to dashboard Cite

Abstract:The standard NACE MR0175 (ISO 15156) requires a maximum hardness value of 23 HRC for 13Cr-4Ni-(Mo) steel grade for sour service, requiring a double tempering heat treatment at temperature in the range 648-691 • C for the first tempering and 593-621 • C for the second tempering. Difficulties in limiting alloy hardness after the tempering of forged mechanical components (F6NM) are often faced. Variables affecting the thermal behavior of 13Cr-4Ni-(Mo) during single and double tempering treatments have been studied by means of transmission electron microscopy (TEM) observations, X-ray diffraction measurements, dilatometry, and thermo-mechanical simulations. It has been found that relatively low Ac 1 temperatures in this alloy induce the formation of austenite phase above 600 • C during tempering, and that the formed, reverted austenite tends to be unstable upon cooling, thus contributing to the increase of final hardness via transformation to virgin martensite. Therefore, it is necessary to increase the Ac 1 temperature as much as possible to allow the tempering of martensite at the temperature range required by NACE without the detrimental formation of virgin martensite upon final cooling. Attempts to do so have been carried out by reducing both carbon (<0.02% C) and nitrogen (<100 ppm) levels. Results obtained herein show final hardness below NACE limits without an unacceptable loss of mechanical strength.

show abstract

“…Due to its excellent mechanical properties in offshore oil and gas industry, it has already become an alternative product to replace duplex stainless steel and austenitic stainless steel [5][6][7]. Supermartensitic stainless steels have distinguished mechanical properties (such as the yield strength is 800-950 MPa, the ultimate tensile strength is 900-1200 MPa, the elongation is 13-18% and the hardness is 26-32 HRC), which depend on the microstructure and chemical composition [6,[8][9][10]. Lu and Li propound that the alloying element changes material properties by modifying the microstructures of the host element [11].…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependent Phase Transformation Kinetics of Reverted Austenite during Tempering in 13Cr Supermartensitic Stainless Steel

Zhang

Yin

et al. 2019

Metals

View full text Add to dashboard Cite

The formation and growth kinetics of the reverted austenite during tempering in 13Cr supermartensitic stainless steel were investigated by a combination X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The reverted austenite precipitated at the martensite blocks, sub-blocks, laths and grain boundaries. The growth kinetics was established by Johnson-Mehl-Avrami (JAM) kinetics equation according to the volume fraction of the equilibrium reverted austenite at room temperature. The Avrami exponent value is 0.5, and the activation energy was estimated to be 369 kJ/mol, the kinetic model indicates that the mechanism of reverted austenite is diffusion-controlled and the growth of reverted austenite closely relies on the diffusion of the nickel (Ni) element. The experimental measured orientations of the reverted austenite are in good agreement with the theoretical ones, implying that the reverted austenite has the same orientation with the surrounding martensite, which meets the Kurdjumov–Sachs (K-S) orientation relationship. The orientation relationships minimize the strain energy of the phase transformation by reducing the crystallographic mismatch between phases.

show abstract

Microstructural Features Affecting Tempering Behavior of 16Cr-5Ni Supermartensitic Steel

Cited by 29 publications

References 13 publications

Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

Study of 13Cr-4Ni-(Mo) (F6NM) Steel Grade Heat Treatment for Maximum Hardness Control in Industrial Heats

Temperature Dependent Phase Transformation Kinetics of Reverted Austenite during Tempering in 13Cr Supermartensitic Stainless Steel

Contact Info

Product

Resources

About