Research ArticleMicrostructure and Hardness of Cold Work Vanadis6 Steel after Subzero Treatment at −140°C

Juraj Durica, Jana Ptacinova, Maria Hudakova, Martin Kusy, and Peter Jurci

Faculty of Materials Science and Technology in Trnava, Slovak University of Technology, Jana Bottu 2781/25,917 24 Trnava, Slovakia

Correspondence should be addressed to Peter Jurci; p.jurci@seznam.cz

Received 25 October 2017; Accepted 9 January 2018; Published 4 March 2018

Academic Editor: Carlos Garcia-Mateo

Copyright © 2018 Juraj Durica et al. .is is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

.e microstructure, phase constitution, and hardness of Cr-V ledeburitic tool steel Vanadis 6 subjected to subzero treatment at−140°C and for different soaking times have been investigated. .e light microscopy, scanning electron microscopy, and X-raydiffraction have been used for microstructural investigations. .e hardness has been evaluated by the Vickers method. .eobtained results assist to draw that subzero treatment reduces the retained austenite amount and increases the population densityof carbides, compared to conventional heat treatment..e extent of decrease in the retained austenite amount makes around 85%,and the increase in population density of small globular carbides was approximately fivefold. High compressive stresses wereidentified in the retained austenite, and their values follow the increase in carbide count..ismakes a serious support to the theoryexplaining the formation of “extra” carbides as a by-product of more complete martensitic transformation. As a result of thementioned microstructural changes, the material hardness increased from 875± 16 HV 10 up to 954.6± 14 HV 10 for con-ventionally quenched and SZT steels, respectively.

1. Introduction

One of the major problems in heat treatment of high-carbonsteels is too high amount of retained austenite, whichappears in their microstructure after room temperaturequenching. For example, Jurci et al. [1] reported that theamount of retained austenite (cR) in the ledeburitic tool steelVanadis 6 was 20.2± 1.6 vol. % after room temperaturequenching from the austenitizing temperature of 1050°C.Retained austenite is an undesirable microstructural featureas it is soft and metastable at low temperatures, and it isamenable to decompose when heavily loaded, for instance.Decomposition of the cR is always connected with di-mensional changes, which can have detrimental effect on thedurability of tools and precise parts. Also, an embrittlementof the materials can occur at these circumstances since thestress-induced cR transformation results in the formation ofeither the martensite or low bainite. .erefore, the retainedaustenite must be eliminated from the tools before use. Oneof the possible ways how the retained austenite can be re-moved is the application of high-temperature tempering.

However, some steel grades cannot be tempered abovea temperature of around 200°C, due to the risk of substantialhardness loss.

Subzero treatment (SZT) is an add-on step in the heattreatment of high-carbon high-alloyed steels where thematerials are cooled down to temperatures well below theroom temperature, held there for a predetermined duration,and reheated slowly to the room temperature. .is kind ofheat treatment leads to considerable alterations in the mi-crostructure of steels, which can be summarized as follows:

(i) SZT steels contain considerably reduced cR amount[1–9].

(ii) As a result of both the extensive plastic deformationand spatial limitations, the martensite of SZT steelsis clearly refined compared to that developed byroom temperature quenching, and it contains en-hanced number of lattice defects [1, 5, 10].

(iii) In many cases, SZT steels contain precipitates oftransient carbides after reheating to the roomtemperature as a result of accelerated precipitation

HindawiAdvances in Materials Science and EngineeringVolume 2018, Article ID 6537509, 7 pageshttps://doi.org/10.1155/2018/6537509

rate caused by various metallurgical effects of SZT[11–14].

(iv) SZT ledeburitic steels contain enhanced popula-tion density of small globular carbides (SGCs)[1–4, 8, 9, 14–19]. .e formation of these carbides isa result of more complete martensitic trans-formation as determined recently [14].

Mentioned microstructural alterations are reflected inhigher as-SZT hardness [1–3, 11, 14, 15], better dimensionalstability of components and tools [20, 21], and “extra” wearperformance [2, 3, 9, 16, 22]. .e toughness and fracturetoughness are, however, worsened [23], except the caseswhere the steels are high-temperature tempered [24, 25].

Despite the basic metallurgical principles being re-sponsible for alterations in the microstructure, mechanicalproperties and tribological performance are rather un-derstood [14], the choice of “optimal” temperature of theSZT is still under debate.

In the middle of the 20th century, it was generally ac-cepted that temperatures of approx. −79°C (−120°F) aresufficient to transform high portion of retained austeniteinto the martensite and thereby make beneficial effects likeadditional wear resistance, increased fatigue strength, andbetter aging stability of steels. Lower temperatures were notused for the SZTas the experiences of heat treaters indicatedthat there is a great risk of failure of tools, due to thermalshocks resulting from the immersion of tools into liquidnitrogen, for instance.

Only much later, a temperature of −196°C was suggestedfor treatment. Practical applications of tools have early shownthat the treatment at the boiling temperature of liquid nitrogenfurther increases the wear resistance and hardness. Based onthese facts, subzero treatment in liquid nitrogen became thestandard processing route, and other temperatures did nothave practical use in SZT. Also, the understanding of processes,which take place at cryotemperatures, has been realized bytreatment of specimens at the temperature of −196°C.

Only few studies suggested other temperatures, for in-stance −140°C [11, 26] or, on the contrary, a temperature ofliquid helium [11, 27] for the treatment of Cr ledeburitic toolsteels. .e obtained experimental results indicate that someprocesses, which are responsible for the abovementionedameliorations in properties, may proceed faster at −140°Cthan at −196°C; thus, this schedule might bring some benefitsinto the SZT. Alternatively, the use of the temperatureof boiling helium (−269°C, 4.2 K) can provide an “extra”driving force for the martensitic transformation and therebyfor the formation of SGCs also. However, it is inevitable thattreatment times would be very long as there is little atomicmovement at such a low temperature [11].

.e main goal of the current experimental works is thento make a comprehensive study on what happens in lede-buritic steels when they are subjected to the SZT at −140°C..e current paper is focused on the investigations of mi-crostructural alternations and their impact on resultinghardness of commercially available PM-manufacturedcold work tool steel Vanadis 6, which was subjected to thesubzero treatment at a temperature of −140°C for different

durations. .e same steel processed by room temperaturequenching as well as the samples after subzero treatment at−196°C has been used as the reference material.

2. Experimental

.e experimental material was the tool steel Vanadis 6 withnominally 2.1% C, 1.0% Si, 0.4% Mn, 6.8% Cr, 1.5% Mo, and5.4% V and Fe as balance, made by PM. .e steel wasdelivered in soft-annealed state (i.e., with ferrite-carbidemicrostructure), Figure 1, and its hardness was 284 HV10..e carbides are distributed uniformly within the matrix,with no preferential orientation.

Samples for the microstructural investigations werecylinders with a diameter of 17mm and height of 6mm.Conventional heat treatment (CHT) consisted of the fol-lowing steps: heating up to the austenitizing temperature of1050°C in a vacuum furnace, holding at the temperature for30min, and nitrogen gas quenching (5 bar). SZT has beencompleted at a temperature of −140°C and for 4, 10, 17, 24,36, and 48 h. No tempering of the steel was carried out inorder to highlight the microstructural changes due to theSZT itself.

Metallographic samples were prepared by standardpreparation line and etched with the Villela–Bain reagentfor the light microscopy or with picric acid for the SEMobservation.

Figure 1: SEM micrograph showing the microstructure of theVanadis 6 steel in as-delivered state.

10 µm

Figure 2: Light micrograph showing the microstructure of theVanadis 6 steel after SZT at −140°C for 17 h.

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.e microstructure was recorded using the light mi-croscope NEOPHOT 32 and the scanning electron micro-scope JEOL JSM 7600 F device equipped with an EDSdetector (Oxford Instruments), at an acceleration voltage of15 kV. For each duration of subzero treatment, quantitativeanalysis of carbides has been done on twenty randomlyacquired SEM micrographs. For details of the categorizationof the carbides, check [1, 28]. X-ray diffraction patterns wererecorded using a Phillips PW 1710 device with filtered Coα1,2characteristic radiation, in the range 45–130° of the two-thetaangle. .e amount of retained austenite cR was determinedaccording to the ASTM E975-13 standard [29]. .e stressvalues in the retained austenite have been calculated fromthe lattice deformation (true strain), assuming pure elasticdeformation (validity of Hook’s law), and considering theYoung modulus to be 225GPa [30].

Macrohardness measurements were completed by theVickers (HV 10) method. Eachmetallographic specimen wasmeasured 5 times, and the mean value and standard de-viation from the measurements were calculated. .e aus-tenite grain size G was determined by the Snyder–Graffmethod by the formula

G � [6.635log(S-G)] + 2.66, (1)

where S-G is the dimensionless Snyder–Graff interceptcount number.

3. Results and Discussion

Figure 2 shows light micrograph of the examined steel afterconventional quenching followed by SZT for 17 h. .emicrostructure consists of matrix and undissolved carbides,which are uniformly distributed throughout the material..e matrix contains the martensite and retained austenite..e original austenitic grains are well visible. .ey are very

fine—the grain size was determined to be 10.26± 0.14according to the Snyder–Graff method.

SEM micrographs, Figures 3(a)–3(d) show typicalmicrostructures of the Vanadis 6 tool steel after CHT andafter SZT at −140°C for different durations. .e micro-structure is composed of the matrix and three types ofcarbides, namely, the eutectic carbides (ECs), secondarycarbides (SCs), and small globular carbides (SGCs). .epopulation density of both the ECs and SCs is invariantover the heat treatment parameter range used. .is isbecause the ECs do not undergo the dissolution duringaustenitizing, and the level of dissolution of the SCs isconstant at fixed austenitizing temperature. .e populationdensity of SGCs increased with holding time at the tem-perature of SZT. .is is clearly evident by comparing themicrostructures in Figures 3(a)–3(d).

Detail SEM micrograph acquired at high magnification,Figure 4, demonstrates that the matrix is composed of themartensite and small amount of the retained austenite..e formations of retained austenite are located in-betweenthe martensitic domains.

.e population density of SGCs as a function of theduration of SZT is shown in Figure 5. It is obvious that thepopulation density of SGCs increased very rapidly up to24 h of soaking time and then rather slightly decreased. .emean values of population density of SGCs were 48×103,176 ×103, 179 ×103, 198 ×103, 209 ×103, 193 ×103, and183×103/mm2 for CHTsamples and SZTsamples for 4, 10, 17,24, 36, and 48 h, respectively. Here, it should be noted that thevalues, with respect to the statistical uncertainty at a level of95%, considerably overlap for the samples treated for 4 and10 h. It is shown that the maximum population density ofSGCs was achieved for 24 h storage time at −140°C. .ereference material treated at −196°C had the maximumpopulation density of SGCs of 193×103/mm2 for 24 h [19].

(a)

SCs

ECs

SGCs

(a)

(b)

SCs SGCs

ECs

(b)

(c)

SCs

ECs

SGCs

(c)

(d)

SGCs

SCs

ECs

(d)

Figure 3: SEM micrographs showing the microstructure of Vanadis 6 steel (a) after CHT, (b) after SZT at −140°C for 4 h, (c) after SZT at−140°C for 24 h, and (d) after SZT at −140°C for 48 h.

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�e obtained results are in excellent agreement withthose presented by other investigators for di�erent Crledeburitic steels [2–4, 7, 18, 22]. �erefore, one can suggestthat the fact that the SZT produces enhanced number andpopulation density of these particles is generally a validphenomenon for the ledeburitic cold work tool steels. In therecent two papers [14, 19], it has been demonstrated that theSZT at −196°C increases the population density of SGCs inthe Vanadis 6 steel. �e values of population density were169×103, 188×103, 193×103, and 160×103/mm2 for thematerial subzero treated for 10, 17, 24, and 48 h, respectively.By comparing the results obtained by two SZT tempera-tures, it is evident that the SZT at −140°C produces ratherhigher population density of SGCs.

�e cR amount decreases considerably with the appli-cation SZT, Table 1. In no-SZT samples, the amount of cRwas 20.2 vol. %, and for SZTsamples with 48 h holding time,it was just 3.24 vol. %.

�e results of retained austenite amount measure-ments are consistent with those obtained by di�erentresearchers and for other Cr and Cr-V ledeburitic steels[3, 4, 7, 9, 22, 31]. �ese researchers have reported that, forinstance, the AISI D2 steel is almost free of cR after SZT

performed at −196°C for 36 h. Alternatively, Gavriljuk et al.[31] established that Cr-V ledeburitic steel X220 CrMoV13-4 contained around 4% of retained austenite afterlong-term SZT at −196°C. It is relevant to note that the cRalways exists in the microstructure of high-carbon high-alloyed ledeburitic steels in their untempered state becausethe martensitic transformation is never completed in thesematerials.

In recent studies, it has been reported that the SZT inliquid nitrogen (−196°C) carried out for 4, 10, 17, 24, and48 h reduces the retained austenite amount to 9.9± 1.6,2.9 ± 0.6, 2.1± 0.5, 2.9± 0.6, and 3.0 ± 0.7 vol. %, re-spectively [1, 14, 19]. It is seen that the cR amount isconsiderably lower for the specimens processed at −140°Cthan that after processing at −196°C for short time treat-ments but the treatments in liquid nitrogen remove the cRmore e�ectively after longer processing times. �ese resultsare counterintuitive on the �rst sight because one canexpect rather stronger e�ect of lower processing temper-ature on the cR amount after short treatment too. Also,at least twice higher cR amounts in the specimens treatedat −140°C seem to be somewhat surprising since the pro-cessing temperature lies well below the characteristicmartensite �nish (Mf) temperature (−69°C). However, itshould be noticed that there is much higher driving forcefor the martensitic transformation at −196°C, that is, thetemperature di�erence between the processing tempera-ture and Mf is much higher for the treatment in liquidnitrogen than in nitrogen gas at −140°C. Lower cR amountafter short time treatment at −140°C, on the contrary, canbe explained by the following consideration: Isothermalmartensitic transformation, which proceeds during thehold at the lowest processing temperature, is connectedwith plastic deformation of freshly formed martensite, asdemonstrated in [31–33]. It is logical to expect that plasticdeformation proceeds faster at −140°C than at −196°C, andthis can act in favour of more pronounced cR reduction inthe early stage of isothermal martensitic transformation.

By comparing the data in Table 1 and the obtained resultsof population density of SGCs, Figure 5, it is obvious thatthere is close relation between these two microstructuralparameters. Similar results were reported for the samematerial after subzero treatment in liquid nitrogen [1, 14].�is indicates that there exists a general validity of the re-lation “the less the retained austenite is, the higher thepopulation density of SGCs is.” In other words, enhancedpopulation density of SGCs can be attributed to morecomplete martensitic transformation.

Table 2 shows calculated hydrostatic stresses in theretained austenite for di�erent SZTsamples. It is shown thatthe compressive stresses in the retained austenite exceed1000MPa and that the highest stresses were developed inthe material that was SZT for 24 h. �ese results are well

240000220000200000180000160000140000120000100000

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GCs

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m2 )

Soaking time in nitrogen vapors at −140°C (h)no-SZT 4 10 17 24 36 48

Figure 5: Population density of SGCs for samples processed byCHT and SZT, with various soaking times in nitrogen vapors at−140°C.

Table 1: Amount of retained austenite (vol. %) in the SZT samplesfor various soaking times (h).

SZT (h) No-SZT 4 10 17 24 36 48cR amount (vol. %) 20.2 3.94 4.64 4.25 4.16 3.6 3.24

Figure 4: Detail SEM micrograph showing the microstructure ofVanadis 6 steel after SZT at −140°C for 24 h, with particular at-tention to the matrix microstructure.

4 Advances in Materials Science and Engineering

consistent with the obtained results by Villa et al. [10] whoreported on high compressive stresses in the retained aus-tenite of 100Cr6 ball bearing steel after application of SZT.Figure 6 shows the dependence of both the populationdensity of SGCs and compressive stress in austenite on theduration of SZT. For these two curves, the correlation co-e¦cient was calculated to be 0.858961. �e correlation co-e¦cient is greater than 0.8; hence, there is a strongdependency of these parameters.

At this place, it is noteworthy once again to pay attentionto the presence of considerably enhanced population densityof SGCs: As well known, the martensitic transformation is

never completed in high-carbon steels. �is is due to verylow martensite �nish (Mf) temperature (it lies well below theroom temperature in most cases) and also due to the positivevolumetric e�ect of the transformation. As a result, com-pressive stresses are built up in the austenite, which hinderfurther progress in the transformation. In SZT, however, thetemperature lies well below the Mf, and this makes a strongdriving force for continuing of the transformation. Asdiscussed and explained recently [14], the SGCs are a by-product of the martensitic transformation that takes placeat cryotemperatures and resulted from the e�ort of thematerial to relax the stresses and thereby enabling the furthermartensitic transformation. In the present study, close cor-relation between the compressive stress in the retained aus-tenite and the population density of SGCs has beenestablished. �is is an additional supporting fact to the theory,which was elaborated and demonstrated recently [14].

�e bulk hardness of SZTVanadis 6 tool steel is shown inFigure 7. �e hardness of CHTsteel was 875± 16 HV 10.�ehardness of the SZT steel soaked in nitrogen vapor for 4, 10,17, 24, 36, and 48 h were 949± 13.5, 949.2± 15.6, 933.2± 16.8,925.2± 13.3, 940.8± 6.4, and 954.6± 14 HV 10, respectively.�ese results infer that the as-quenched bulk hardness ofVanadis 6 steel is improved due to SZT, whereas the im-provement is almost independent on the duration of subzerotreatment at −140°C. In other words, this kind of treatmentincreases the hardness compared to the state after CHT, butthe e�ect of SZTcan be considered as minimal for durationsof this treatment longer than 4 h.

�e enhancement of as-SZT bulk hardness of SZT steelover the CHTone can be simply referred to the reduction ofsoft-retained austenite and to the increased populationdensity of small globular carbides. �e current results can beconsidered to be in an excellent agreement with those re-ported for subzero-treated AISI D2 [2, 3, 21, 34, 35] and AISID3 steel [4, 18, 36].

4. Conclusions

�e Vanadis 6 ledeburitic tool steel has been austenitized,quenched, and subzero treated at a temperature of −140°Cfor di�erent durations. �e obtained experimental resultslead to following major conclusions:

(1) �e Vanadis 6 tool steel is composed of the matrix(the martensite and the retained austenite), ECs, SCs,and SGCs (with a size up to 500 nm, mostly around100 nm).

(2) �e population density of small globular carbides isseveral times increased due to the SZT, witha maximum after SZT realized for a soaking time of24 h. �e treatment at −140°C leads to rather higherpopulation density of these particles than thetreatment at a temperature of boiling nitrogen.

(3) �e application of SZT reduces the amount ofretained austenite in Vanadis 6 tool steel consider-ably. Moreover, it has been found that the treatmentat −140°C acts more e�ectively in reduction ofretained austenite in early stages of isothermal c to α′

1000

950

900

850

800

750

700

Har

dnes

s HV

10

Soaking time in nitrogen vapors at −140°C (h)no-SZT 4 10 17 24 36 48

Figure 7: Bulk hardness HV 10 of the Vanadis 6 after SZT withdi�erent soaking times in nitrogen vapors.

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Compressive stressPopulation density of SGCs

17 24 36 48

Figure 6: Dependence of the population density of SGCs andcompressive stress in the retained austenite for specimens pro-cessed for various soaking times, at a temperature of −140°C.

Table 2: Compressive stress σ (MPa) in the specimen SZT forvarious durations.

SZT (h) Lattice strain ε (−) Compressive stress σ (MPa)4 0.005539 124610 0.006517 146617 0.006746 151824 0.007199 162036 0.006786 152748 0.006411 1442

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transformation, while the treatment at a temperatureof boiling nitrogen leads to approx. half-fold retainedaustenite amount after long time treatment.

(4) .e as-quenched hardness of the Vanadis 6 tool steelmanifests a moderate increase after SZT.

(5) .ere is a strong dependency of population densityof SGCs and compressive stresses in the retainedaustenite. .is fact supports the latest theory on theformation of enhanced population density of car-bides, as a product of more complete martensitictransformation.

Conflicts of Interest

.e authors declare that they have no conflicts of interest.

Acknowledgments

.e authors acknowledge that this paper is a result of ex-periments realized within the project VEGA 1/0264/17. Inaddition, this publication is the result of the projectimplementation “Centre for Development and Applicationof Advanced Diagnostic Methods in Processing of Metallicand Non-Metallic Materials–APRODIMET,” ITMS:26220120014, supported by the Research & DevelopmentOperational Programme funded by the ERDF.

References

[1] P. Jurci, M. Domankova, L. Caplovic et al., “Microstructureand hardness of sub-zero treated and no tempered P/MVanadis 6 ledeburitic tool steel,” Vacuum, vol. 111, pp. 92–101, 2015.

[2] D. Das, A. K. Dutta, and K. K. Ray, “Sub-zero treatments ofAISI steel: part II wear behavior,” Materials Science andEngineering: A, vol. 527, no. 9, pp. 2194–2206, 2010.

[3] D. Das and K. K. Ray, “Structure-property correlation of cub-zero treated AISI D2 steel,”Materials Science and Engineering:A, vol. 541, pp. 45–60, 2012.

[4] K. Amini, A. Akhbarizadeh, and S. Javadpour, “Investigatingthe effect of holding duration on the microstructure of 1.2080tool steel during the deep cryogenic treatment,” Vacuum,vol. 86, no. 10, pp. 1534–1540, 2012.

[5] A. I. Tyshchenko, W. .eisen, A. Oppenkowski et al., “Low-temperature martensitic transformation and deep cryogenictreatment of a tool steel,” Materials Science and Engineering:A, vol. 527, no. 26, pp. 7027–7039, 2010.

[6] P. Jurci, J. Sobotova, P. Salabova, O. Prikner, B. Sustarsic, andD. Jenko, “Subzero treatment of P/M Vanadis 6 ledeburitictool steel,” International Heat Treatment and Surface Engi-neering, vol. 7, no. 3, pp. 125–128, 2013.

[7] A. Akhbarizadeh, S. Javadpour, K. Amini, and A. H. Yaghtin,“Investigating the effect of ball milling during the deepcryogenic heat treatment of the 1.2080 tool steel,” Vacuum,vol. 90, pp. 70–74, 2013.

[8] D. N. Collins, “Deep cryogenic treatment of tool steels:a review,” Heat Treatment of Metals, vol. 2, pp. 40–42, 1996.

[9] A. Akhbarizadeh, M. A. Golozar, A. Shafeie, and M. Kholghy,“Effects of austenitizing time on wear behaviour of D6 toolsteel after deep cryogenic treatment,” Journal of Iron and SteelResearch, International, vol. 16, no. 6, pp. 29–32, 2009.

[10] M. Villa, K. Pantleon, and M. A. J. Somers, “Evolution ofcompressive strains in retained austenite during sub-zeroCelsius martensite formation and tempering,” Acta Materi-alia, vol. 65, pp. 383–392, 2014.

[11] P. F. Stratton, “Optimizing nano-carbide precipitation in toolsteels,” Materials Science and Engineering: A, vol. 449–451,pp. 809–812, 2007.

[12] M. J. Van Genderen, A. Boettger, R. J. Cernik, andE. J. Mittemeijer, “Early stages of decomposition in iron-carbon and iron-nitrogen martensites: diffraction analysisusing synchrotron radiation,” Metallurgical Transactions A,vol. 24, no. 9, pp. 1965–1973, 1993.

[13] M. Preciado and M. Pellizzari, “Influence of deep cryogenictreatment on the thermal decomposition of Fe-C martensite,”Journal of Materials Science, vol. 49, no. 23, pp. 8183–8191,2014.

[14] P. Jurci, “Sub-zero treatment of cold work tool steels–metallurgical background and the effect on microstructureand properties,” HTM Journal of Heat Treatment and Ma-terials, vol. 72, no. 1, pp. 62–68, 2017.

[15] D. N. Collins and J. Dormer, “Deep cryogenic treatment ofa D2 Cold-work tool steel,” Heat Treatment of Metals, vol. 3,p. 71, 1997.

[16] K. Amini, A. Akhbarizadeh, and S. Javadpour, “Investigatingthe effect of the quench environment on the final micro-structure and wear behaviour of 1.2080 tool steel after deepcryogenic heat treatment,” Materials & Design, vol. 45,pp. 316–322, 2013.

[17] A. Akhbarizadeh, K. Amini, and S. Javadpour, “Effect of si-multaneous magnetic field and deep cryogenic heat treatmenton the microstructure of 1.2080 tool steel,” Materials &Design, vol. 35, pp. 484–490, 2012.

[18] K. Amini, A. Akhbarizadeh, and S. Javadpour, “Effect of deepcryogenic treatment on the formation of nano-sized carbidesand the wear behaviour of D2 tool steel,” International Journalof Minerals, Metallurgy, and Materials, vol. 19, pp. 795–799,2012.

[19] P. Jurci, M. Kusy, J. Ptacinova, V. Kuracina, andP. Priknerova, “Long-term sub-zero treatment of P/MVanadis 6 ledeburitic tool steel–a preliminary study,”Manufacturing Technology, vol. 15, p. 41, 2015.

[20] H. Berns, “Restaustenit in ledeburitischen Chromstahlen undseine Umwandlung durch Kaltumformen, Tiefkuhlen undAnlassen,” HTM Journal of Heat Treatment and Materials,vol. 29, p. 236, 1974, (in German).

[21] CH. Surberg, P. Stratton, and K. Lingenhoele, “.e effect ofsome heat treatment parameters on the dimensional stabilityof AISI D2,” Cryogenics, vol. 48, no. 1-2, pp. 42–47, 2008.

[22] D. Das, A. K. Dutta, and K. K. Ray, “Optimization of theduration of cryogenic processing to maximize wear resistanceof ASIS D2 steel,” Cryogenics, vol. 49, no. 5, pp. 176–184, 2009.

[23] D. Das, R. Sarkar, A. K. Dutta, and K. K. Ray, “Influence ofsub-zero treatments on fracture toughness of AISI D2 steel,”Materials Science and Engineering: A, vol. 528, no. 2,pp. 589–603, 2010.

[24] J. Sobotova, P. Jurci, and I. Dlouhy, “.e effect of subzerotreatment on microstructure, fracture toughness, and wearresistance of Vanadis 6 tool steel,” Materials Science andEngineering: A, vol. 652, pp. 192–204, 2016.

[25] J. Ptacinova, V. Sedlicka, M. Hudakova, I. Dlouhy, andP. Jurci, “Microstructure–Toughness relationships in sub-zerotreated and tempered Vanadis 6 steel compared to conven-tional treatment,” Materials Science and Engineering: A,vol. 702, pp. 241–258, 2017.

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[26] W. Reitz and J. Pendray, “Cryoprocessing of materials: a re-view of current status,” Materials and Manufacturing Pro-cesses, vol. 16, no. 6, pp. 829–840, 2001.

[27] Z. Zurecki, “Cryogenic quenching of steel revisited,” inProceedings of the 23rd Heat Treating Society Conference,D.Herring and R.Hill, Eds., vol. 106, Pittsburgh, PA, USA, 2005.

[28] P. Bılek, J. Sobotova, and P. Jurci, “Evaluation of the mi-crostructural changes in Cr-V ledeburitic tool steel dependingon the austenitization temperature,” Materials and Technol-ogy, vol. 45, p. 489, 2011.

[29] ASTM E975-13, Standard Practice for X-Ray Determination ofRetained Austenite in Steel with Near Random Crystallo-graphic Orientation, vol. 3, ASTM Book of Standards, WestConshohocken, PA, USA, 2004.

[30] Vanadis 6 Super Clean, “High performance powder metal-lurgical cold work tool steel,” http://www.uddeholm.com.

[31] V. G. Gavriljuk, W. .eisen, V. V. Sirosh et al., “Low-temperature martensitic transformation in tool steels in re-lation to their deep cryogenic treatment,” Acta Materialia,vol. 61, no. 5, pp. 1705–1715, 2013.

[32] J. Pietikainen, “Effects of the Aging of martensite on its de-formation characteristic and on fracture in Fe-Ni-Si-C steel,”Journal of the Iron and Steel Institute, vol. 1, p. 74, 1968.

[33] P. Jurci, M. Domankova, M. Hudakova, J. Ptacinova,M. Pasak, and P. Palcek, “Characterization of microstructureand tempering response of conventionally quenched, short-and long-time sub-zero treated PM Vanadis 6 ledeburitic toolsteel,”Materials Characterization, vol. 134, pp. 398–415, 2017.

[34] M. Pellizzari and A. Molinari, “Deep cryogenic treatment ofcold work tool steel,” in Proceedings of the 6th InternationalTooling Conference, J. Bergstrom, G. Fredriksson, M. Johansson,O. Kotik, and F. Auvander, Eds., vol. 547, Karlstad University,Karlstad, Sweden, 2002.

[35] D. Das, K. K. Ray, and A. K. Dutta, “Influence of temperatureof sub-zero treatments on the wear behaviour of die steel,”Wear, vol. 267, no. 9-10, pp. 1361–1370, 2009.

[36] A. Akhbarizadeh and S. Javadpour, “Investigating the effect ofas-quenched vacancies in the final microstructure of 1.2080tool steel during the deep cryogenic heat treatment,”MaterialsLetters, vol. 93, pp. 247–250, 2013.

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