# Comparative Study on Hot Metal Flow Behaviour of Virgin and Rejuvenated Heat Treatment Creep Exhausted P91 Steel

^{1}

^{2}

^{3}

^{4}

^{*}

## Abstract

**:**

^{−1}to a total strain of 0.6 using Gleeble

^{®}3500 equipment. The results showed that the flow stress largely depends on the deformation conditions. The flow stress for the two steels increased with an increase in strain rate at a given deformation temperature and vice versa. The flow stress–strain curves exhibited dynamic recovery as the softening mechanism. The material constants determined using Arrhenius constitutive equations were: the stress exponent, which was 5.76 for steel A and 6.67 for steel B; and the apparent activation energy, which was: 473.1 kJ mol

^{−1}for steel A and 564.5 kJmol

^{−1}for steel B. From these results, steel A exhibited better workability than steel B. Statistical parameters analyses showed that the flow stress for the two steels had a good correlation between the experimental and predicted data. Pearson’s correlation coefficient (R) was 0.97 for steel A and 0.98 for steel B. The average absolute relative error (AARE) values were 7.62% for steel A and 6.54% for steel B. This study shows that the Arrhenius equations can effectively describe the flow stress behaviour of P91 steel, and this method is applicable for industrial metalworking process.

## 1. Introduction

_{3}, and tempering is conducted below the lower critical temperature, Ac

_{1}[13]. Various authors [2,13,14,15] have applied different normalisation and tempering temperatures for P91 steel within the Ac

_{3}and Ac

_{1}requirements. Pandey et al. [2] reported the phase transformation temperatures of P91 as 810 °C to 825 °C (Ac

_{1}) and 912 °C to 930 °C (Ac

_{3}). According to Abe [16], the Ac

_{1}was 800 to 830 °C and Ac

_{3}890 to 940 °C in P91. The variations in heat treatment temperatures of P91 are due to minor differences in chemical composition (especially Ni + Mn), rate of heating and prior austenite grain boundaries (PAGBs) [14]. The American Society of Mechanical Engineers (ASME) [16] recommended an austenitisation temperature of 1040 to 1080 °C and tempering at 730 to 780 °C in P91 pipes.

_{23}C

_{6}(M = chromium, iron, tungsten and molybdenum) carbides along the PAGBs, reducing their pinning effect and hence reducing the strengthening mechanism [19].

_{23}C

_{6}and MX (M = Niobium, Vanadium and X-carbon) precipitates [2]. During normalisation, the homogenisation of the microstructure occurs, causing an untempered lath microstructure with a small number of precipitates and a high dislocation density. Tempering causes the precipitation of the M

_{23}C

_{6}carbides along the grain boundaries and MX particles in the matrix [19]. The high dislocation density and the M

_{23}C

_{6}precipitates are responsible for the pinning of lath boundaries, while MX precipitates prevent dislocation movement [2,17]. The heat treatment process, therefore, restores the effects of the creep process and provides a stable microstructure for the steel to achieve high creep strength [20].

## 2. Materials and Methods

^{®}3500 equipment were as follows: deformation temperatures of 900 °C, 950 °C, 1000 °C, and 1050 °C and strain rates of 0.01 s

^{−1}, 0.1 s

^{−1}, 1 s

^{−1}, and 10 s

^{−1}. The samples were deformed to a total strain of 0.6. Before testing, an R-type thermocouple was welded at the midpoint on the samples to monitor temperature during the deformation process. Figure 3 is a schematic diagram illustrating the thermal deformation process used in this study. All the specimens were heated at 5 °C/s to 1100 °C and held isothermally for 180 s before cooling to the deformation temperature.

## 3. Results

#### 3.1. Flow Stress–Strain Curves

^{−1}, 0.1 s

^{−1}, 1 s

^{−1}, and 10 s

^{−1}. The results show that the measured flow stress values in the stress–strain curves were higher than the friction-corrected values. This variation may be due to the interfacial friction effect experienced at the test sample and anvil interface.

_{o}and h

_{f}are the initial and final height of the sample and d

_{o}and d

_{f}are the initial and final diameter of the sample.

_{sat}) region. The results show that DRV involved the softening mechanism. Similar flow stress–strain curve behaviour results are available in the literature for creep-resistant steels [42,43].

#### 3.2. Constitutive Equation and Material Constants

^{−1}K

^{−1}).

^{−1}and high temperature [50]. Equation (6) is a hyperbolic sine function equation developed by Sellars and Tegart [51] to be applicable to a wide range of stresses (both high and low). Equations (4)–(6) can also give Equations (7) and (9) [25]:

#### 3.3. Activation Energy and Stress Exponent

#### 3.4. Constitutive Model of Flow Stresses

#### 3.5. Verification of Constitutive Models

^{−1}, 5 s

^{−1}, 10 s

^{−1}and 15 s

^{−1}. In Samantaray et al. [21], the temperature for hot deformation was between 850 °C and 1100 °C and the strain rates were 0.001 s

^{−1}, 0.1 s

^{−1}and 100 s

^{−1}. Validation by both models thus signified satisfactory levels of confidence in the respective constitutive equations to predict flow stresses.

_{i}is the flow stress from the experiment, P

_{i}is the flow stress predicted from constitutive equations, and E and P are the average flow stress values of experimental data and the predicted data, respectively. N is the sum of data points.

#### 3.6. Comparison of Constitutive Equations

## 4. Conclusions

^{−1}), and the following conclusions were drawn:

- The flow stress–strain curves show that the flow stress increased with an increase in strain rate (0.01 s
^{−1}to 10 s^{−1}) and decreased with an increase in temperature (900 °C to 1050 °C) for the two steels. The flow stress–strain curves exhibited a DRV+WH as the deformation mechanism. - The apparent activation energy of steel A was 473.08 kJ/mol, and for steel B it was 564.48 kJ/mol. These Q-values were much higher compared to the self-diffusion energy of iron in austenite (270 kJmol
^{−1}) - The mathematical constitutive models for steel A and steel B to a total strain of 0.6 are as given in Equations (22) and (23).$$\dot{\epsilon}=9.97885\times {10}^{18}{\left[sinh\left(0.006916{\sigma}_{ss}\right)\right]}^{5.755175}\left[\frac{-473.0843}{RT}\right]$$$$\dot{\epsilon}=9.58432\times {10}^{22}{\left[sinh\left(0.00647{\sigma}_{ss}\right)\right]}^{6.66945}\left[\frac{-564.4791}{RT}\right]$$
- The constitutive models were validated using Pearson’s correlation coefficient, R and the average absolute relative error, AARE. For steel A, R was 0.97, and AARE was 7.62%. For Steel B, R was 0.98, and AARE was 6.54%. The developed models were used interchangeably with acceptable accuracy. Using the model for steel A on steel B, R was 0.96, and AARE was 7.19%. Similarly, using the steel B model on steel A, the R was 0.95, and AARE was 8.36%.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Gutiérrez, N.Z.; Alvarado, J.V.; de Cicco, H.; Danón, A. Microstructural Study of Welded Joints in a High Temperature Martensitic-ferritic ASTM A335 P91 Steel. Procedia Mater. Sci.
**2015**, 8, 1140–1149. [Google Scholar] [CrossRef] [Green Version] - Pandey, C.; Mahapatra, M.M.; Kumar, P.; Saini, N. Some studies on P91 steel and their weldments. J. Alloys Compd.
**2018**, 743, 332–364. [Google Scholar] [CrossRef] - Sharma, A.; Verma, D.K.; Kumaran, S. Effect of post weld heat treatment on microstructure and mechanical properties of Hot Wire GTA welded joints of SA213 T91 steel. Mater. Today Proc.
**2018**, 5, 8049–8056. [Google Scholar] [CrossRef] - Oñoro, J. Martensite microstructure of 9–12% Cr steels weld metals. J. Mater. Process. Technol.
**2006**, 180, 137–142. [Google Scholar] [CrossRef] - Dak, G.; Pandey, C. A critical review on dissimilar welds joint between martensitic and austenitic steel for power plant application. J. Manuf. Process.
**2020**, 58, 377–406. [Google Scholar] [CrossRef] - Danielsen, H.K. Review of Z phase precipitation in 9–12 wt-%Cr steels. Mater. Sci. Technol.
**2016**, 32, 126–137. [Google Scholar] [CrossRef] [Green Version] - Li, H.; Mitchell, D. Microstructural Characterization of P91 Steel in the Virgin, Service Exposed and Post-Service Re-Normalized Conditions. Steel Res. Int.
**2013**, 84, 1302–1308. [Google Scholar] [CrossRef] [Green Version] - Hurtado-Noreña, C.; Danón, C.; Luppo, M.; Bruzzoni, P. Evolution of Minor Phases in a P91 Steel Normalized and Tempered at Different Temperatures. Procedia Mater. Sci.
**2015**, 8, 1089–1098. [Google Scholar] [CrossRef] [Green Version] - Falat, L.; Čiripová, L.; Homolová, V.; Džupon, M.; Džunda, R.; Kovaľ, K. The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel. Materials
**2021**, 14, 6076. [Google Scholar] [CrossRef] [PubMed] - Hosseini, S.S.; Nategh, S.; Ekrami, A.-A. Microstructural evolution in damaged IN738LC alloy during various steps of rejuvenation heat treatments. J. Alloys Compd.
**2012**, 512, 340–350. [Google Scholar] [CrossRef] - Jamalpour, A.; Hajjari, E.; Baghal, S.M.L. Effect of rejuvenation heat treatment on microstructure and hot corrosion resistance of a service-exposed nickel-based gas turbine blade. Mater. Res. Express
**2019**, 6, 1265c6. [Google Scholar] [CrossRef] - Subbiah, R.; Rahel; Sravika, A.; Ambika, R.; Srujana, A.; Navya, E. Investigation on Microstructure and Mechanical Properties of P91 Alloy Steel Treated With Normalizing Process—A Review. Mater. Today Proc.
**2019**, 18, 2265–2269. [Google Scholar] [CrossRef] - Peng, N.G.; Ahmad, B.; Muhamad, M.R.; Ahadlin, M. Phase Transformation of P91 Steels upon Cooling after Short Term Overheating above Ac1 and Ac3 Temperature. Adv. Mater. Res.
**2013**, 634–638, 1756–1765. [Google Scholar] [CrossRef] - Vimalan, G.; Ravichandran, G.; Muthupandi, V. Phase Transformation Behaviour in P91 During Post Weld Heat Treatment: A Gleeble Study. Trans. Indian Inst. Met.
**2017**, 70, 875–885. [Google Scholar] [CrossRef] - Pandey, C.; Giri, A.; Mahapatra, M. Effect of normalizing temperature on microstructural stability and mechanical properties of creep strength enhanced ferritic P91 steel. Mater. Sci. Eng. A
**2016**, 657, 173–184. [Google Scholar] [CrossRef] - Abe, F. Grade 91 Heat-Resistant Martensitic Steel; Woodhead Publishing Limited: Sawston, UK, 2014; Volume 91, pp. 3–51. [Google Scholar] [CrossRef]
- Yan, W.; Wang, W.; Shan, Y.-Y.; Yang, K. Microstructural stability of 9–12%Cr ferrite/martensite heat-resistant steels. Front. Mater. Sci.
**2013**, 7, 1–27. [Google Scholar] [CrossRef] - Pandey, C.; Mahapatra, M.; Kumar, P.; Saini, N. Homogenization of P91 weldments using varying normalizing and tempering treatment. Mater. Sci. Eng. A
**2018**, 710, 86–101. [Google Scholar] [CrossRef] - Hald, J. Microstructure and long-term creep properties of 9–12% Cr steels. Int. J. Press. Vessels Pip.
**2008**, 85, 30–37. [Google Scholar] [CrossRef] - Pandey, C.; Giri, A.; Mahapatra, M. Evolution of phases in P91 steel in various heat treatment conditions and their effect on microstructure stability and mechanical properties. Mater. Sci. Eng. A
**2016**, 664, 58–74. [Google Scholar] [CrossRef] - Samantaray, D.; Mandal, S.; Bhaduri, A. Constitutive analysis to predict high-temperature flow stress in modified 9Cr–1Mo (P91) steel. Mater. Des.
**2010**, 31, 981–984. [Google Scholar] [CrossRef] - Niu, X.; Shen, L.; Chen, C.; Zhou, J.; Chen, L. An Arrhenius-type constitutive model to predict the deformation behavior of Sn0.3Ag0.7Cu under different temperature. J. Mater. Sci. Mater. Electron.
**2019**, 30, 14611–14620. [Google Scholar] [CrossRef] - Quan, G.-Z.; Li, G.-S.; Wang, Y.; Lv, W.-Q.; Yu, C.-T.; Zhou, J. A characterization for the flow behavior of as-extruded 7075 aluminum alloy by the improved Arrhenius model with variable parameters. Mater. Res.
**2013**, 16, 19–27. [Google Scholar] [CrossRef] [Green Version] - Yang, X.; Li, W. Flow Behavior and Processing Maps of a Low-Carbon Steel During Hot Deformation. Met. Mater. Trans. A Phys. Metall. Mater. Sci.
**2015**, 46, 6052–6064. [Google Scholar] [CrossRef] - Obiko, J.; Chown, L.; Whitefield, D.; Bodunrin, M. Metal flow behaviour and processing maps of high heat resistant steel during hot compression. Int. J. Adv. Manuf. Technol.
**2022**, 121, 4153–4167. [Google Scholar] [CrossRef] - Lakshmi, A.A.; Rao, C.S.; Gangadhar, J.; Srinivasu, C.; Singh, S.K. Review of Processing Maps and Development of Qualitative Processing Maps. Mater. Today Proc.
**2017**, 4, 946–956. [Google Scholar] [CrossRef] - Prasad, Y.; Rao, K. Processing maps for hot deformation of rolled AZ31 magnesium alloy plate: Anisotropy of hot workability. Mater. Sci. Eng. A
**2008**, 487, 316–327. [Google Scholar] [CrossRef] - Xiao, Z.-B.; Huang, Y.-C.; Liu, Y. Modeling of Flow Stress of 2026 Al Alloy under Hot Compression. Adv. Mater. Sci. Eng.
**2016**, 2016, 3803472. [Google Scholar] [CrossRef] [Green Version] - Kumar, A.; Pandey, S.M.; Pandey, C. Dissimilar weldments of ferritic/martensitic grade P92 steel and Inconel 617 alloy: Role of groove geometry on mechanical properties and residual stresses. Arch. Civ. Mech. Eng.
**2022**, 23, 54. [Google Scholar] [CrossRef] - Kaibyshev, R.; Mishnev, R.; Fedoseeva, A.; Dudova, N. The Role of Microstructure in Creep Strength of 9–12% Cr Steels. Mater. Sci. Forum
**2017**, 879, 36–41. [Google Scholar] [CrossRef] - Bhanu, V.; Pandey, S.M.; Gupta, A.; Pandey, C. Dissimilar weldments of P91 and Incoloy 800HT: Microstructure, mechanical properties, and residual stresses. Int. J. Press. Vessels Pip.
**2022**, 199, 104782. [Google Scholar] [CrossRef] - Chatterjee, A.; Dutta, A.; Sk, B.; Mitra, R.; Bhaduri, A.K.; Chakrabarti, D. Effect of Microalloy Precipitates on the Microstructure and Texture of Hot-Deformed Modified 9Cr-1Mo Steel. Met. Mater. Trans. A Phys. Metall. Mater. Sci.
**2017**, 48, 2410–2424. [Google Scholar] [CrossRef] - Obiko, J. Friction correction of flow stress-strain curve in the upsetting process. IOP SciNotes
**2021**, 2, 014401. [Google Scholar] [CrossRef] - Li, Y.; Onodera, E.; Chiba, A. Friction Coefficient in Hot Compression of Cylindrical Sample. Mater. Trans.
**2010**, 51, 1210–1215. [Google Scholar] [CrossRef] [Green Version] - Roebuck, B.; Lord, J.; Brooks, M.; Loveday, M.; Sellars, C.; Evans, R. Measurement of flow stress in hot axisymmetric compression tests. Mater. High Temp.
**2006**, 23, 59–83. [Google Scholar] [CrossRef] - Ghosh, S.; Somani, M.C.; Setman, D.; Mula, S. Hot Deformation Characteristic and Strain Dependent Constitutive Flow Stress Modelling of Ti + Nb Stabilized Interstitial Free Steel. Met. Mater. Int.
**2020**, 27, 2481–2498. [Google Scholar] [CrossRef] - Hu, M.; Dong, L.; Zhang, Z.; Lei, X.; Yang, R.; Sha, Y. Correction of Flow Curves and Constitutive Modelling of a Ti-6Al-4V Alloys. Metals
**2018**, 8, 256. [Google Scholar] [CrossRef] [Green Version] - Samantaray, D.; Mandal, S.; Bhaduri, A. Optimization of hot working parameters for thermo-mechanical processing of modified 9Cr–1Mo (P91) steel employing dynamic materials model. Mater. Sci. Eng. A
**2011**, 528, 5204–5211. [Google Scholar] [CrossRef] - Jonas, J.J.; Quelennec, X.; Jiang, L.; Martin, É. The Avrami kinetics of dynamic recrystallization. Acta Mater.
**2009**, 57, 2748–2756. [Google Scholar] [CrossRef] - Lin, Y.; Chen, X.-M. A critical review of experimental results and constitutive descriptions for metals and alloys in hot working. Mater. Des.
**2011**, 32, 1733–1759. [Google Scholar] [CrossRef] - Bodunrin, M.O.; Chown, L.H.; van der Merwe, J.W.; Alaneme, K.K. Hot working behaviour of experimental Ti-4.5Al-1 V-3Fe alloy with initial lamellar microstructure. Int. J. Adv. Manuf. Technol.
**2020**, 106, 1901–1916. [Google Scholar] [CrossRef] - Obiko, J.; Chown, L.; Whitefield, D.; Bodunrin, M. Understanding hot workability of power plant P92 creep resistant steels using dynamic material modelling (DMM) and microstructural evolution. Int. J. Interact. Des. Manuf.
**2022**. [Google Scholar] [CrossRef] - Obiko, J.O.; Chown, L.H.; Whitefield, D.J. Warm deformation behaviour of P92 steel. Mater. Res. Express
**2019**, 6, 1265j7. [Google Scholar] [CrossRef] - Wang, H.; Wang, W.; Zhai, R.; Ma, R.; Zhao, J.; Mu, Z. Constitutive Equations for Describing the Warm and Hot Deformation Behavior of 20Cr2Ni4A Alloy Steel. Metals
**2020**, 10, 1169. [Google Scholar] [CrossRef] - Akbari, Z.; Mirzadeh, H.; Cabrera, J.-M. A simple constitutive model for predicting flow stress of medium carbon microalloyed steel during hot deformation. Mater. Des.
**2015**, 77, 126–131. [Google Scholar] [CrossRef] [Green Version] - He, J.; Zhang, D.; Zhang, W.; Qiu, C.; Zhang, W. Constitutive Equation and Hot Compression Deformation Behavior of Homogenized Al–7.5Zn–1.5Mg–0.2Cu–0.2Zr Alloys. Materials
**2017**, 10, 1193. [Google Scholar] [CrossRef] - Samantaray, D.; Mandal, S.; Bhaduri, A. A comparative study on Johnson Cook, modified Zerilli–Armstrong and Arrhenius-type constitutive models to predict elevated temperature flow behaviour in modified 9Cr–1Mo steel. Comput. Mater. Sci.
**2009**, 47, 568–576. [Google Scholar] [CrossRef] - Mirzadeh, H.; Cabrera, J.M.; Najafizadeh, A. Constitutive relationships for hot deformation of austenite. Acta Mater.
**2011**, 59, 6441–6448. [Google Scholar] [CrossRef] - Alsagabi, S. High Temperature Deformation Behavior of P92 Steel. Trans. Indian Inst. Met.
**2015**, 69, 1513–1518. [Google Scholar] [CrossRef] - Bodunrin, M.O. Flow stress prediction using hyperbolic-sine Arrhenius constants optimised by simple generalised reduced gradient refinement. J. Mater. Res. Technol.
**2020**, 9, 2376–2386. [Google Scholar] [CrossRef] - Sellars, C.; McTegart, W. On the mechanism of hot deformation. Acta Met.
**1966**, 14, 1136–1138. [Google Scholar] [CrossRef] - Menapace, C.; Sartori, N.; Pellizzari, M.; Straffelini, G. Hot Deformation Behavior of Four Steels: A Comparative Study. J. Eng. Mater. Technol.
**2018**, 140, 021006. [Google Scholar] [CrossRef] - Cabrera, J.M.; Jonas, J.J.; Prado, J.M. Flow behaviour of medium carbon microalloyed steel under hot working conditions. Mater. Sci. Technol.
**1996**, 12, 579–585. [Google Scholar] [CrossRef] - Baktash, R.; Mirzadeh, H. A Simple Constitutive Model for Prediction of Single-Peak Flow Curves Under Hot Working Conditions. J. Eng. Mater. Technol.
**2016**, 138, 021004. [Google Scholar] [CrossRef] - Alaneme, K.K.; Babalola, S.A.; Bodunrin, M.O. On the prediction of hot deformation mechanisms and workability in Al6063/Ni and Al6063/steel composites using hyperbolic-sine constitutive equation. Mater. Today Proc.
**2021**, 38, 942–948. [Google Scholar] [CrossRef] - McQueen, H.J.; Ryan, N.D. Constitutive analysis in hot working. Mater. Sci. Eng. A
**2002**, 322, 43–63. [Google Scholar] [CrossRef] - Carsí, M.; Peñalba, F.; Rieiro, I.; Ruano, O.A. High temperature workability behaviour of a modified P92 steel. Int. J. Mater. Res.
**2011**, 102, 1378–1383. [Google Scholar] [CrossRef] [Green Version] - Zhou, D.; Xu, X.; Mao, H.; Yan, Y.; Nieh, T.; Lu, Z. Plastic flow behaviour in an alumina-forming austenitic stainless steel at elevated temperatures. Mater. Sci. Eng. A
**2014**, 594, 246–252. [Google Scholar] [CrossRef] - Mehtonen, S.; Karjalainen, L.; Porter, D. Hot deformation behavior and microstructure evolution of a stabilized high-Cr ferritic stainless steel. Mater. Sci. Eng. A
**2013**, 571, 1–12. [Google Scholar] [CrossRef] - Obiko, J.O.; Mwema, F.M.; Shangwira, H. Forging optimisation process using numerical simulation and Taguchi method. SN Appl. Sci.
**2020**, 2, 713. [Google Scholar] [CrossRef] [Green Version] - Mwema, F.; Obiko, J.; Mahamood, R.; Adediran, A.; Bodunrin, M.; Akinlabi, E.; Jen, T. Constitutive analysis of hot forming process of P91 steel: Finite element method approach. Adv. Mater. Process. Technol.
**2021**, 8, 1182–1193. [Google Scholar] [CrossRef] - Cai, J.; Li, F.; Liu, T.; Chen, B.; He, M. Constitutive equations for elevated temperature flow stress of Ti–6Al–4V alloy considering the effect of strain. Mater. Des.
**2011**, 32, 1144–1151. [Google Scholar] [CrossRef] - Gao, F.; Liu, Z.; Misra, R.D.K.; Liu, H.; Yu, F. Constitutive modeling and dynamic softening mechanism during hot deformation of an ultra-pure 17%Cr ferritic stainless steel stabilized with Nb. Met. Mater. Int.
**2014**, 20, 939–951. [Google Scholar] [CrossRef]

**Figure 7.**(

**a**,

**b**) Plots of ln (έ) versus ln σ and ln (έ) versus σ for the determination of n′ in steel A and steel B and (

**c**,

**d**) for determination of β in steel A and steel B.

**Figure 8.**(

**a**,

**b**) Plots of ln έ versus σ and ln (sinh (σα)) for determination of n and (

**c**,

**d**) are plots of ln (sinh (σα)) versus (1000)/T to determine S value for steel A and steel B, respectively.

**Figure 11.**(

**a**) Steel A model used to predict flow stresses of steel B. (

**b**) Steel B model to predict flow stresses in Steel A.

Cr | C | Mn | Mo | V | Nb | W | Ni | Si | Fe | P | Cu | Mg | Sn |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|

9.189 | 0.1 | 0.447 | 0.885 | 0.191 | 0.076 | ˂0.01 | 0.158 | 0.254 | 88.01 | 0.02 | 0.086 | 0.016 | 0.006 |

P91 | ή | β | η | ɑ | S | Q (kJmol^{−1}) | ln A |
---|---|---|---|---|---|---|---|

Steel A | 7.79 | 0.054 | 5.76 | 0.0069 | 9.89 | 473.08 | 9.98 × 10^{18} |

Steel B | 9.03 | 0.058 | 6.67 | 0.0065 | 10.18 | 564.48 | 9.58 × 10^{22} |

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Maube, S.; Obiko, J.; Van der Merwe, J.; Mwema, F.; Klenam, D.; Bodunrin, M.
Comparative Study on Hot Metal Flow Behaviour of Virgin and Rejuvenated Heat Treatment Creep Exhausted P91 Steel. *Appl. Sci.* **2023**, *13*, 4449.
https://doi.org/10.3390/app13074449

**AMA Style**

Maube S, Obiko J, Van der Merwe J, Mwema F, Klenam D, Bodunrin M.
Comparative Study on Hot Metal Flow Behaviour of Virgin and Rejuvenated Heat Treatment Creep Exhausted P91 Steel. *Applied Sciences*. 2023; 13(7):4449.
https://doi.org/10.3390/app13074449

**Chicago/Turabian Style**

Maube, Shem, Japheth Obiko, Josias Van der Merwe, Fredrick Mwema, Desmond Klenam, and Michael Bodunrin.
2023. "Comparative Study on Hot Metal Flow Behaviour of Virgin and Rejuvenated Heat Treatment Creep Exhausted P91 Steel" *Applied Sciences* 13, no. 7: 4449.
https://doi.org/10.3390/app13074449