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Investigation on Microstructure and Mechanical Properties of P91 Alloy Steel Treated With Normalizing Process - A Review
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ICMPC-20019
Inveestigationn on Miccrostructture and Mechannical Propperties of o P91 A Alloy Steeel Treatted Withh Normaalizing Prrocess - A Revieew Ram Suubbiaha, Md.Rahelb*, A Sravikac, R.Ambikkad, A.Srujaanae, E.Navvyaf a
Associatee Professor, Depaartment of Mechannical Engineeringg, Gokaraju Ranggaraju Institute off Engineering andd Technology,Hydderabad,,India b* M.T Tech,, Departmennt of Mechanical E Engineering, Gokkaraju Rangarajuu Institute of Engiineering and Techhnology,Hyderabaad India c, d,e,f B B.Tech, Departmeent of Mechanicall Engineering, Gookaraju Rangarajuu Institute of Enggineering and Technology,Hyderabbad, India
Abstract
A Review w on organizeed investigatioon on microstrructure and m mechanical prooperties of P911 Alloy steel treated with varying teemperatures of o Normalizingg Heat Treatm ment process w were analyzedd in this paperr. The Compoonents in the Microstruucture displayeed an improveement in Grainn structure, Laath breadth andd then with thhe increasing temperatures of Heat ttreatment we found reducttion in the A Area Fraction in precipitatees of microstrructure. The m microscopic observatioon and calcuulation is proocessed usingg Field Emisssion Scanninng Electron M Microscope aand Optical microscoppe, grain size and area fracction are meassured from thhe micrographs. Tests like ttensile strengtth, Hardness and toughhness tests werre conducted on o the Normallized specimenns. © 2019 Elseevier Ltd. All righhts reserved. Selection annd peer-review unnder responsibilityy of the 9th Internnational Conferennce of Materials P Processing and Chharacterization, IC CMPC-2019 Keywords:P P91 steel, Normallizing, precipitate size, tensile strenngth, hardness, touughness.
1. Introd duction With an a excellent qquality of greeater heat connductivity, low wer coefficiennt of thermal expansion, grreater weldability with stress erosion resistancce, splitting annd oxidation, the Ferritic/M Martensitic stteels are mostt commonly Saroja et al [1]]. In order to applied inn manufacturinng of High heaat segments off atomic poweer plants invesstigated by S.S create annd improve thhe effectiveneess of power plants whosee working connditions rangees over 873K K, there is a necessity to discover the material at specific w working condittions as detaiiled by R.Kannnan et al[6].. create and K, there is a nnecessity to improve the effectivenness of powerr plants whosse working coonditions rangges over 873K discover tthe material aat specific worrking conditionns as detailed by R.Kannann et al[6]. In adddition to theese qualities, the main merits of P91 alloy steel is iits high creep disrupt strenggth which is prroposed by S.H Haribabu[7].
* Correesponding author. Tel.: +91 81217335897 E-maiil address: [email protected] m
2214-7853© © 2019 Elsevier L Ltd. All rights reseerved. Selection annd peer-review unnder responsibilityy of the 9th Internnational Conferennce of Materials P Processing and Chharacterization, IC CMPC-2019
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The steels in which the Chromium percentage by weight ranges from 9% to 13% are being usually used for Power plants equipments studied by C.Pandey [2].The Normalizing process shows an effective impact on the microstructural constituents of the steel details given by T.Shaktivel [8]. So to achieve and improve the desired mechanical properties and microstructural functions, heat treatment is performed. Normalizing at different temperatures have been operated for Several hours with a controlled cooling conditions based on alloy content in the steel. In the present investigation P91 steel named as ASTM A334T has been normalized by Nitin Saini [18], T.Sreshta [9] at temperatures ranging from 9500C to 11500C. 1.1. Material The P91 steel is examines under spectro-material examination, the plate was exhibited to an underlying heat treatment at 10500C for half hour so as to homogenize the microstructure. This treated material is taken as the raw sample so as to perform different normalizing heating operations the finding is supported by C.Pandey et al[14]. The steel (ASTM A334) bars of 55 mm x 12 mm x 2 mm measurements had been manufactured from the raw material as proposed by F. Kafexhiu et al [15]. The chemical composition of P91 steel specimen is found in spectroscopy as, C- 0.1%; Mn- 0.4%; Si-0.024%; Cr8.90%; Mo- 1.0%; Ni- 0.10% and the rest is Fe. 1.2. Procedure Standard metallographic techniques are used for Samples to undergo microstructure and hardness examinations. Villella's reagent scratch is used for raw samples to investigate the microstructures with the help of optical microscope (OM) and scanning electron microscope, a magnifying instrument (SEM) followed by C. Pandey et al[2]. Transmission electron microscopy (TEM) analysis of heat subjected samples were done by reducing the thickness upto 70mm mechanically by using SiC sheet under hot flowing water. Plates of 3 mm thick have been separated through distance across passed through the twofold electrolytic fly diminishing using 10 percent perchloric corrosive and methanol arrangement as an electrolytic reactant. As per X. Tao et al [10] Fly diminishing has been done at 238 K and at the 20 volts of voltage. The carbon copy is extracted from the set up of a scratched test for considering the precipitates. By conducting Vicker’s hardness test at the load of 5 kg-f and hold period of 15 s, hardness examination of raw specimen and heat subjected steel tests have been estimated The ductile samples with flat head barrel shaped having 4.0 mm breadth and 28.6 mm measure of length of different normalized conditions have been created for the heat subjected samples. Elastic tests at normal temperature have been completed at steady cross-head speed with ostensible strain rate in air. 1.3. Heat Treatment The Specimens of P91 alloy steel is subjected to underlying Normalizing heat treatment with temperatures varying from 9500C to 11500C for about 60 minutes and then after cooling it is held at hardening temperature of 7600C for 120 minutes. The Normalizing process is performed in an electric heater, suitable for achieving the most extreme temperature of 1500 °C as said by X. Tao et al [10]. To start with, Austenitization formation had been finished before these samples were completed for heat treating based on which the normalizing temperature/time were picked so that normalizing was done on every raw sample by a temperature from 9500C – 1150 °C for 1 h. The Standardized specimen were cooled in air to normal temperature, before performing the heat treatment operation. The specimen were chopped for Tensile, Charpy’s strength, hardness, also microstructure (Optical and SEM) tests in order to contemplate the effect of normalizing temperature, L.Maddi et al[11]. At that point, these standardized sampless were exposed to a treating temperature of 760 °C for 120 mins. In the meanwhile of treatment, the samples were air cooled to room temperature. To contemplate the result of treating temperature, the specimens were cut for tractable, strength, hardness, Optical and SEM tests.
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1.4. Metaallographic D Description P Pre-determine ed metallograpphic procedurees were follow wed to examinne the raw Saamples for miicrostructure along witth hardness ass well as tougghness tests. T The micro-harrdness calculaation of un-treeated specimeen and heattreated saamples of P91 steel was connveyed with V Vickers Hardness Tester, at the weight off 500 g and hoold period of 10 s. X-rray-beam diff ffraction (XRD D) of sampless was projecteed on D-8 Brruker AXS ddiffractometer in order to discover, the different stage structurres in differennt normalizingg operations, X XRD investigation was donne with 0.2° To play out a static pliable test for raw P91 steel and speed by utilizing Cu ttarget proposed by V.Thomoos et al[13].. T m ductille samples weere set up from m recently standardized annd tempered heat treatted conditionss, level sub measure samples L L. Maddi et all[11]. The ducctile testing m machine, Instroon 5982 was used u at room ttemperature with w a steady m ductility testss. strain ratee of 6.66*10−44/s to perform E Energy disperrsive X-beam m spectroscopyy, EDS of bbreak surfacess was done tto estimate thhe effect of normaliziing temperatuure on the com mponent rate.. Charpy duraability tests w were led to coontemplate thhe results of normaliziing temperaturre on toughnesss of P91 steell demonstratedd by C.Pandeyy et al[14]. 2. Resultts and Discusssion 2.1. Micrrostructure pree heat treatmeent T raw un-trreated P91 stteel was found with martennsitic microsttructure with countless chaanges at the The earlier auustenitic grain limits (PAGB Bs) and fine acccelerates insiide grid area oor subgrain lim mits as appearred in as Fig 3.1 referrred by Nitin Saaini et al [18]. T EDS exam The mination of haastens at the P PAGBs affirm ms the nearnesss Cr-rich M233C6 is encouraaged. It was likewise sseen those coaarse white parrticles presentt at the PAGB Bs were enhannced with Cr aand Mo as conntrasted and fine encoourages presennt inside the grrain inside, foor sample leann in Cr and M Mo by Saini et al [18]. It waas di cult to demonstrrate the nearneess of little sizze accelerates of VC, NbN,, VN, WC andd NbC inside the subgrain limit and in the netwoork, however, the EDS invesstigation of whhite particles at a the PAGBs and in the latttice affirmed tthe nearness of MX-tyype encouragess. The raw un--treated P91 stteel had an esttimated grain size of about 39.50. 3 The EDS S results in thee Matrix regioon of the untrreated sample gives the eleemental compposition as: C-- 4.19%; Si0.11%; V V- 0.37%; Cr- 88.15%; Fe- 844.68%; Mo- 0.31%; W- 2.199%: as in Fig 33.1.(a).
Figg.3.1. SEM at 5000X
Fig.33.1(a). EDS in the Matrix Reegion
2.2. Micrrostructure posst heat treatmeent U Using the SEM M micrographs obtained thee new arrangem ment of martennsitic structuree is observed oon P91 steel by Saini et al[18] steeel at different normalizing ttemperatures i.e., from 95000C – 1150 °C C. The standaardized steel samples eessentially porrtrayed strip m martensitic kinnd of structuree with clear P PAGBs with reference r to N Nitin Saini et al[18] Figg 3.2 unmistaakably shows the nearness of strip marteensite as colleective/parcels inside the PA AGBs. From Nitin sainni et al[18], itt tends to be seen that thee arrangement of crisp marrtensite increm ments with ann increase in
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micrograph unn-boxes the neearness of stripp martensite seettles in the neeighborhood normaliziing temperaturre. The SEM m martensittic network. The P91 steel hhas an inclinattion to frame martensite unnder heater or air cooling. T The width of strip limitt and dissolutiion of acceleraates were observed to be uppgraded with eexpanding thee normalizing temperature from 9500 °C to 1150 °C. ° EDS exam mination of thhe standardizeed samples waas done and thhe elemental ccomposition results in the Matrix arre given as : C C- 5.84% ; Si- 0.22%;V- 0.118%;Cr- 8.67% %; Fe- 83.06% %; Mo- 0.36% %; W- 1.39% and as shoown below Fig 3.2 and Fig 3.2 (a).
Fiig.3.2. Seconddary Electron M Micrograph
F Fig.3.2.(a) EDS S of treated saample in Matriix region
2.3. Harddness Samplle hardness in the raw un-treeated and various treated samples are estiimated, the varriation in harddness of P91 steel at diifferent normaalizing processs is studied byy Saini et all [18]. It has beeen observed frrom the resultss of vicker’s hardness test that by inncreasing the normalizing temperature t thhe hardness ddecreased, it iss due to increease in grain size studiied by T. Sreshhta et al [9]. H However, the rranget of reduuction in hardnness of the sam mples that aree normalized at 11500C was found too be comparattively high, whhereas the rannge of reductioon in hardnesss of the samples treated at 9500C waas seen to be comparativelly less due too fine grain siize (more graain boundariess) in the case of samples treated att 11500C as peer F. Vodopiveecet al[16]. Laarger grain sizze led to lowerr residues of carbides c in caase of higher normaliziing which is aagain reflectedd in the low aarea fraction oof the residue in the high nnormalizing opperation and high area fraction of the residues in tthe low normaalizing operatioon as shown inn above Fig 3.2. 2.4. Tougghness F the un-treeated P91 steel the Charpy ttoughness wass estimated arround 62 Joulees at normal ttemperature, For the changges in toughnness for various heat treatm ment with refference from A.Giri[12] It was discoverred that the strength ddiminished as normalizing ttemperature inncrements yet is enough morre when contrrasted with un-treated P91 steel from m studies of Saini et al[18]. This is becauuse of the graiin coarsening and heat stress. With the expansion e in normaliziing temperaturre, the essentiial cause of ddecrease in durrability of P91 steel is coarrsening of auxxiliary stage particles aand alternate ffactors are deccohesion at haasten grid inteerface and spliitting of optionnal stage carbiide particles from the sstudies by A.G Giri et al[12]. 3. Conclu usion T Ductile nnature of the material is foound to increaase with the iincreasing tem The mperature of N Normalizing process annd at a temperrature of 100000C the ductiliity is found deecreased. Due to the accelerration in the cooarsening of secondaryy stage carbiddes at PAGB aalso in sub-graain lattice it iss found that bbrittling effect occurs in P91 alloy steel after seveeral normaliziing and hardeening operatioons. When coombined with static tensilee testing at geeneral room temperatuure the brittlinng effect is expponentially artticulated in touughness testinng, because off which the touughness was decreasedd with increassing in the heaat treatment teemperature. Hence H keepingg in mind the vision for ideeal nature of strength, ductility and toughness off steel the moost ultimate nnormalizing teemperature haas been recom mmended till 10000C foor P91 steel. Referencces [1] S. S Saroja, A. Dassgupta, R. Divvakar, S. Raju,, E. Mohandass, M. Vijayalaakshmi, K. Bhhanu Sankara Rao, R B. Raj, Deveelopment and characterizatiion of advancced 9Crferriticc/martensitic ssteels for fission and fusionn reactors, J. Nucll. Mater. 409 (2011)131–13 ( 39.
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[2] C. Pandey, A. Giri, M.M. Mahapatra, Evolution of phases in P91 steel in variousheat treatment conditions and their effect on microstructure stability andmechanical properties, Mater. Sci. Eng. A 664 (2016) 58–74. [3] C. Pandey, A. Giri, M.M. Mahapatra, P. Kumar, Characterization of microstructureof HAZs in as-welded and service condition of P91 pipe weldments, Met. Mater. Int.23 (1) (2017) 148–162. [4] C. Pandey, M.M. Mahapatra, Effect of groove design and post weld heat treatmenton microstructure and mechanical properties of P91 steel weld, J. Mater. Eng.Perform. 25 (7) (2016) 2761–2775. [5] C. Pandey, M.M. Mahapatra, P. Kumar, N. Saini, Effect of normalization andtempering on microstructure and mechanical properties of V-groove and narrow-groove P91 pipe weldments, Mater. Sci. Eng. A 685 (2017) 39–49. [6] R. Kannan, V. Sankar, R. Sandhya, M.D. Mathew, Comparative evaluation of thelow cycle fatigue behaviors of and steels, Procedia Eng. 55 (2013) 149–153. [7] S. Haribabu, A. Amarendra, R. Rajaraman, C.S. Sundar, Microstructural charac-terization of ferritic/martensitic steel by positron annihilation spectroscopy, J.Phys. 443 (2013) 1–6. [8] T. Sakthivel, K. Laha, P. Parameswaran, S. PanneerSelvi, K.S. Chandravathi,M.D. Mathew, Effect of thermal aging on microstructure and mechanical propertiesof steel, Trans. Indian Inst. Met. 68 (3) (2015) 411–421. [9] T. Shrestha, S.F. Alsagabi, I. Charit, G.P. Potirniche, M.V. Glazoff, Effect of heattreatment on microstructure and hardness of grade 91 steel, Metals 5 (2015)131–149. [10] X. Tao, J. Gu, L. Han, Characterization of precipitates in X12CrMoWVNbN10-1-1steel during heat treatment, J. Nucl. Mater. 452 (2014) 557–564. [11] L. Maddi, A.R. Ballal, D.R. Peshwe, R.K. Paretkar, K. Laha, M.D. Mathew, Effect oftempering temperature on the stress rupture properties of Grade 92 steel, Mater.Sci. Eng. A 639 (2015) 431–438. [12] A. Giri, M.M. Mahapatra,C.pandey, Effect of normalizing temperature onmicrostructural stability and mechanical properties of creep strength enhancedferritic steel, Mater. Sci. Eng. A 657 (2016) 173–184. [13] V. Thomas Paul, S. Saroja, M. Vijayalakshmi, Microstructural stability of modified9Cr–1Mo steel during long term exposures at elevated temperatures, J. Nucl.Mater. 378 (2008) 273–281. [14] C. Pandey, M.M. Mahapatra, Evolution of phases during tempering of P91 steel at760 °C for varying tempering time and their effect on microstructure andmechanical properties, Proc. Inst. Mech. Eng., Part E: J. Process Mech. Eng. (2016)0954408916656678. [15] F. Kafexhiu, F. Vodopivec, J. Vojvodi-Tuma, Effect of tempering on the roomtemperature mechanical properties of X20CRMoV121 and steels, Mater. Technol.46 (5) (2012) 459–464. [16] F. Vodopivec, D. Kmeti, J. Vojvodi-Tuma, D.A. Skobir, Effect of operatingtemperature on microstructure and creep resistance of 20CrMoV121, Mater.Tehnol. 38 (5) (2004) 233–239. ASTM A370, Standered Test Methods and Definitions for Mechanical Testing of Steel Products. [18] Nitin Sainia,, Chandan Pandeya,, Manas Mohan Mahapatrab,Characterization and evaluation of mechanical properties of CSEF P92 steel for varying normalizing temperature. (2017)
ScienceeDirect Materialss Today: Proceediings 18 (2019) 22265–2269
www.m materialstoday.com m/proceedings
ICMPC-20019
Inveestigationn on Miccrostructture and Mechannical Propperties of o P91 A Alloy Steeel Treatted Withh Normaalizing Prrocess - A Revieew Ram Suubbiaha, Md.Rahelb*, A Sravikac, R.Ambikkad, A.Srujaanae, E.Navvyaf a
Associatee Professor, Depaartment of Mechannical Engineeringg, Gokaraju Ranggaraju Institute off Engineering andd Technology,Hydderabad,,India b* M.T Tech,, Departmennt of Mechanical E Engineering, Gokkaraju Rangarajuu Institute of Engiineering and Techhnology,Hyderabaad India c, d,e,f B B.Tech, Departmeent of Mechanicall Engineering, Gookaraju Rangarajuu Institute of Enggineering and Technology,Hyderabbad, India
Abstract
A Review w on organizeed investigatioon on microstrructure and m mechanical prooperties of P911 Alloy steel treated with varying teemperatures of o Normalizingg Heat Treatm ment process w were analyzedd in this paperr. The Compoonents in the Microstruucture displayeed an improveement in Grainn structure, Laath breadth andd then with thhe increasing temperatures of Heat ttreatment we found reducttion in the A Area Fraction in precipitatees of microstrructure. The m microscopic observatioon and calcuulation is proocessed usingg Field Emisssion Scanninng Electron M Microscope aand Optical microscoppe, grain size and area fracction are meassured from thhe micrographs. Tests like ttensile strengtth, Hardness and toughhness tests werre conducted on o the Normallized specimenns. © 2019 Elseevier Ltd. All righhts reserved. Selection annd peer-review unnder responsibilityy of the 9th Internnational Conferennce of Materials P Processing and Chharacterization, IC CMPC-2019 Keywords:P P91 steel, Normallizing, precipitate size, tensile strenngth, hardness, touughness.
1. Introd duction With an a excellent qquality of greeater heat connductivity, low wer coefficiennt of thermal expansion, grreater weldability with stress erosion resistancce, splitting annd oxidation, the Ferritic/M Martensitic stteels are mostt commonly Saroja et al [1]]. In order to applied inn manufacturinng of High heaat segments off atomic poweer plants invesstigated by S.S create annd improve thhe effectiveneess of power plants whosee working connditions rangees over 873K K, there is a necessity to discover the material at specific w working condittions as detaiiled by R.Kannnan et al[6].. create and K, there is a nnecessity to improve the effectivenness of powerr plants whosse working coonditions rangges over 873K discover tthe material aat specific worrking conditionns as detailed by R.Kannann et al[6]. In adddition to theese qualities, the main merits of P91 alloy steel is iits high creep disrupt strenggth which is prroposed by S.H Haribabu[7].
* Correesponding author. Tel.: +91 81217335897 E-maiil address: [email protected] m
2214-7853© © 2019 Elsevier L Ltd. All rights reseerved. Selection annd peer-review unnder responsibilityy of the 9th Internnational Conferennce of Materials P Processing and Chharacterization, IC CMPC-2019
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The steels in which the Chromium percentage by weight ranges from 9% to 13% are being usually used for Power plants equipments studied by C.Pandey [2].The Normalizing process shows an effective impact on the microstructural constituents of the steel details given by T.Shaktivel [8]. So to achieve and improve the desired mechanical properties and microstructural functions, heat treatment is performed. Normalizing at different temperatures have been operated for Several hours with a controlled cooling conditions based on alloy content in the steel. In the present investigation P91 steel named as ASTM A334T has been normalized by Nitin Saini [18], T.Sreshta [9] at temperatures ranging from 9500C to 11500C. 1.1. Material The P91 steel is examines under spectro-material examination, the plate was exhibited to an underlying heat treatment at 10500C for half hour so as to homogenize the microstructure. This treated material is taken as the raw sample so as to perform different normalizing heating operations the finding is supported by C.Pandey et al[14]. The steel (ASTM A334) bars of 55 mm x 12 mm x 2 mm measurements had been manufactured from the raw material as proposed by F. Kafexhiu et al [15]. The chemical composition of P91 steel specimen is found in spectroscopy as, C- 0.1%; Mn- 0.4%; Si-0.024%; Cr8.90%; Mo- 1.0%; Ni- 0.10% and the rest is Fe. 1.2. Procedure Standard metallographic techniques are used for Samples to undergo microstructure and hardness examinations. Villella's reagent scratch is used for raw samples to investigate the microstructures with the help of optical microscope (OM) and scanning electron microscope, a magnifying instrument (SEM) followed by C. Pandey et al[2]. Transmission electron microscopy (TEM) analysis of heat subjected samples were done by reducing the thickness upto 70mm mechanically by using SiC sheet under hot flowing water. Plates of 3 mm thick have been separated through distance across passed through the twofold electrolytic fly diminishing using 10 percent perchloric corrosive and methanol arrangement as an electrolytic reactant. As per X. Tao et al [10] Fly diminishing has been done at 238 K and at the 20 volts of voltage. The carbon copy is extracted from the set up of a scratched test for considering the precipitates. By conducting Vicker’s hardness test at the load of 5 kg-f and hold period of 15 s, hardness examination of raw specimen and heat subjected steel tests have been estimated The ductile samples with flat head barrel shaped having 4.0 mm breadth and 28.6 mm measure of length of different normalized conditions have been created for the heat subjected samples. Elastic tests at normal temperature have been completed at steady cross-head speed with ostensible strain rate in air. 1.3. Heat Treatment The Specimens of P91 alloy steel is subjected to underlying Normalizing heat treatment with temperatures varying from 9500C to 11500C for about 60 minutes and then after cooling it is held at hardening temperature of 7600C for 120 minutes. The Normalizing process is performed in an electric heater, suitable for achieving the most extreme temperature of 1500 °C as said by X. Tao et al [10]. To start with, Austenitization formation had been finished before these samples were completed for heat treating based on which the normalizing temperature/time were picked so that normalizing was done on every raw sample by a temperature from 9500C – 1150 °C for 1 h. The Standardized specimen were cooled in air to normal temperature, before performing the heat treatment operation. The specimen were chopped for Tensile, Charpy’s strength, hardness, also microstructure (Optical and SEM) tests in order to contemplate the effect of normalizing temperature, L.Maddi et al[11]. At that point, these standardized sampless were exposed to a treating temperature of 760 °C for 120 mins. In the meanwhile of treatment, the samples were air cooled to room temperature. To contemplate the result of treating temperature, the specimens were cut for tractable, strength, hardness, Optical and SEM tests.
R. Subbiiah et al. / Materiials Today: Proceeedings 18 (2019) 2265–2269
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1.4. Metaallographic D Description P Pre-determine ed metallograpphic procedurees were follow wed to examinne the raw Saamples for miicrostructure along witth hardness ass well as tougghness tests. T The micro-harrdness calculaation of un-treeated specimeen and heattreated saamples of P91 steel was connveyed with V Vickers Hardness Tester, at the weight off 500 g and hoold period of 10 s. X-rray-beam diff ffraction (XRD D) of sampless was projecteed on D-8 Brruker AXS ddiffractometer in order to discover, the different stage structurres in differennt normalizingg operations, X XRD investigation was donne with 0.2° To play out a static pliable test for raw P91 steel and speed by utilizing Cu ttarget proposed by V.Thomoos et al[13].. T m ductille samples weere set up from m recently standardized annd tempered heat treatted conditionss, level sub measure samples L L. Maddi et all[11]. The ducctile testing m machine, Instroon 5982 was used u at room ttemperature with w a steady m ductility testss. strain ratee of 6.66*10−44/s to perform E Energy disperrsive X-beam m spectroscopyy, EDS of bbreak surfacess was done tto estimate thhe effect of normaliziing temperatuure on the com mponent rate.. Charpy duraability tests w were led to coontemplate thhe results of normaliziing temperaturre on toughnesss of P91 steell demonstratedd by C.Pandeyy et al[14]. 2. Resultts and Discusssion 2.1. Micrrostructure pree heat treatmeent T raw un-trreated P91 stteel was found with martennsitic microsttructure with countless chaanges at the The earlier auustenitic grain limits (PAGB Bs) and fine acccelerates insiide grid area oor subgrain lim mits as appearred in as Fig 3.1 referrred by Nitin Saaini et al [18]. T EDS exam The mination of haastens at the P PAGBs affirm ms the nearnesss Cr-rich M233C6 is encouraaged. It was likewise sseen those coaarse white parrticles presentt at the PAGB Bs were enhannced with Cr aand Mo as conntrasted and fine encoourages presennt inside the grrain inside, foor sample leann in Cr and M Mo by Saini et al [18]. It waas di cult to demonstrrate the nearneess of little sizze accelerates of VC, NbN,, VN, WC andd NbC inside the subgrain limit and in the netwoork, however, the EDS invesstigation of whhite particles at a the PAGBs and in the latttice affirmed tthe nearness of MX-tyype encouragess. The raw un--treated P91 stteel had an esttimated grain size of about 39.50. 3 The EDS S results in thee Matrix regioon of the untrreated sample gives the eleemental compposition as: C-- 4.19%; Si0.11%; V V- 0.37%; Cr- 88.15%; Fe- 844.68%; Mo- 0.31%; W- 2.199%: as in Fig 33.1.(a).
Figg.3.1. SEM at 5000X
Fig.33.1(a). EDS in the Matrix Reegion
2.2. Micrrostructure posst heat treatmeent U Using the SEM M micrographs obtained thee new arrangem ment of martennsitic structuree is observed oon P91 steel by Saini et al[18] steeel at different normalizing ttemperatures i.e., from 95000C – 1150 °C C. The standaardized steel samples eessentially porrtrayed strip m martensitic kinnd of structuree with clear P PAGBs with reference r to N Nitin Saini et al[18] Figg 3.2 unmistaakably shows the nearness of strip marteensite as colleective/parcels inside the PA AGBs. From Nitin sainni et al[18], itt tends to be seen that thee arrangement of crisp marrtensite increm ments with ann increase in
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micrograph unn-boxes the neearness of stripp martensite seettles in the neeighborhood normaliziing temperaturre. The SEM m martensittic network. The P91 steel hhas an inclinattion to frame martensite unnder heater or air cooling. T The width of strip limitt and dissolutiion of acceleraates were observed to be uppgraded with eexpanding thee normalizing temperature from 9500 °C to 1150 °C. ° EDS exam mination of thhe standardizeed samples waas done and thhe elemental ccomposition results in the Matrix arre given as : C C- 5.84% ; Si- 0.22%;V- 0.118%;Cr- 8.67% %; Fe- 83.06% %; Mo- 0.36% %; W- 1.39% and as shoown below Fig 3.2 and Fig 3.2 (a).
Fiig.3.2. Seconddary Electron M Micrograph
F Fig.3.2.(a) EDS S of treated saample in Matriix region
2.3. Harddness Samplle hardness in the raw un-treeated and various treated samples are estiimated, the varriation in harddness of P91 steel at diifferent normaalizing processs is studied byy Saini et all [18]. It has beeen observed frrom the resultss of vicker’s hardness test that by inncreasing the normalizing temperature t thhe hardness ddecreased, it iss due to increease in grain size studiied by T. Sreshhta et al [9]. H However, the rranget of reduuction in hardnness of the sam mples that aree normalized at 11500C was found too be comparattively high, whhereas the rannge of reductioon in hardnesss of the samples treated at 9500C waas seen to be comparativelly less due too fine grain siize (more graain boundariess) in the case of samples treated att 11500C as peer F. Vodopiveecet al[16]. Laarger grain sizze led to lowerr residues of carbides c in caase of higher normaliziing which is aagain reflectedd in the low aarea fraction oof the residue in the high nnormalizing opperation and high area fraction of the residues in tthe low normaalizing operatioon as shown inn above Fig 3.2. 2.4. Tougghness F the un-treeated P91 steel the Charpy ttoughness wass estimated arround 62 Joulees at normal ttemperature, For the changges in toughnness for various heat treatm ment with refference from A.Giri[12] It was discoverred that the strength ddiminished as normalizing ttemperature inncrements yet is enough morre when contrrasted with un-treated P91 steel from m studies of Saini et al[18]. This is becauuse of the graiin coarsening and heat stress. With the expansion e in normaliziing temperaturre, the essentiial cause of ddecrease in durrability of P91 steel is coarrsening of auxxiliary stage particles aand alternate ffactors are deccohesion at haasten grid inteerface and spliitting of optionnal stage carbiide particles from the sstudies by A.G Giri et al[12]. 3. Conclu usion T Ductile nnature of the material is foound to increaase with the iincreasing tem The mperature of N Normalizing process annd at a temperrature of 100000C the ductiliity is found deecreased. Due to the accelerration in the cooarsening of secondaryy stage carbiddes at PAGB aalso in sub-graain lattice it iss found that bbrittling effect occurs in P91 alloy steel after seveeral normaliziing and hardeening operatioons. When coombined with static tensilee testing at geeneral room temperatuure the brittlinng effect is expponentially artticulated in touughness testinng, because off which the touughness was decreasedd with increassing in the heaat treatment teemperature. Hence H keepingg in mind the vision for ideeal nature of strength, ductility and toughness off steel the moost ultimate nnormalizing teemperature haas been recom mmended till 10000C foor P91 steel. Referencces [1] S. S Saroja, A. Dassgupta, R. Divvakar, S. Raju,, E. Mohandass, M. Vijayalaakshmi, K. Bhhanu Sankara Rao, R B. Raj, Deveelopment and characterizatiion of advancced 9Crferriticc/martensitic ssteels for fission and fusionn reactors, J. Nucll. Mater. 409 (2011)131–13 ( 39.
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