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Sefer, B., Gaddam, R., Rovira, J. J., Mateo, A., Antti, M.-L. & Pederson, R. (2016). Chemical milling effect on the low cycle fatigue properties of cast Ti-6Al-2Sn-4Zr-2Mo alloy (ed.). International Journal of Fatigue, 92(1), 193-202
Open this publication in new window or tab >>Chemical milling effect on the low cycle fatigue properties of cast Ti-6Al-2Sn-4Zr-2Mo alloy
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2016 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 92, no 1, p. 193-202Article in journal (Refereed) Published
Abstract [en]

The current research work presents the chemical milling effect on the low cycle fatigue properties of cast Ti-6Al-2Sn-4Zr-2Mo alloy. Chemical milling treatment is one of the final steps in manufacturing titanium alloy components that removes the brittle alpha-case layer formed during various thermal processes. The treatment includes immersion of the components in solutions containing hydrofluoric (HF) and nitric (HNO3) acids in relevant molar ratios. Although this treatment demonstrates advantages in handling components with complex net geometries, it may have detrimental effects on the surface, by introducing pitting and/or intergranular corrosion and thereby adversely affecting in particular the fatigue strength. The first series of specimens were tested in as-machined condition. Two more series were, prior to fatigue testing, subjected to 5 and 60 minutes chemical milling treatment. It was found that the fatigue lives were substantially decreased for the chemically treated specimens. The fractographic investigation of all mechanically tested samples revealed multiple fatigue crack initiation sites in the chemically milled samples. These cracks were located either at the prior beta grain boundary or the prior beta grain boundary triple joints. The prior beta grain boundaries were found to have deep ditch-like appearance which depth increased with increasing milling time. These ditch-like grain boundaries acts as stress raisers and thereby promote early fatigue crack initiation and thus lower fatigue life.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-3804 (URN)10.1016/j.ijfatigue.2016.07.003 (DOI)000383930200019 ()2-s2.0-84978771831 (Scopus ID)1a417aff-661b-4192-bd0c-6380c8f83b53 (Local ID)1a417aff-661b-4192-bd0c-6380c8f83b53 (Archive number)1a417aff-661b-4192-bd0c-6380c8f83b53 (OAI)
Note

Validerad; 2016; Nivå 2; 20160706 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gaddam, R., Sefer, B., Pederson, R. & Antti, M.-L. (2015). Oxidation and alpha–case formation in Ti–6Al–2Sn–4Zr–2Mo alloy (ed.). Paper presented at . Materials Characterization, 99, 166-174
Open this publication in new window or tab >>Oxidation and alpha–case formation in Ti–6Al–2Sn–4Zr–2Mo alloy
2015 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 99, p. 166-174Article in journal (Refereed) Published
Abstract [en]

Isothermal heat treatments in ambient air were performed on wrought Ti–6Al–2Sn–4Zr–2Mo (Ti–6242) material at 500, 593 and 700 °C for times up to 500 hours. In presence of oxygen at elevated temperatures simultaneous reactions occurred in Ti–6242 alloy, which resulted in formation of an oxide scale and a layer with higher oxygen concentration (termed as alpha–case). Total weight gain analysis showed that there was a transition in the oxidation kinetics. At 500 °C, the oxidation kinetics obeyed cubic relationship up to 200 hours and thereafter changed to parabolic at prolonged exposure times. At 593 °C, it followed parabolic relationship. After heat treatment at 700 °C, the oxidation obeyed parabolic relationship up to 200 hours and thereafter changed to linear at prolonged exposure times. The observed transition is believed to be due to the differences observed in the oxide scale. The activation energy for parabolic oxidation was estimated to be 157 kJ/mol. In addition, alpha–case layer was evaluated using optical microscope, electron probe micro analyser and microhardness tester. The thickness of the alpha–case layer was found to be a function of temperature and time, increasing proportionally, and following parabolic relationship. The activation energy for formation of alpha–case layer was estimated to be 153 kJ/mol.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-4759 (URN)10.1016/j.matchar.2014.11.023 (DOI)000350085900020 ()2-s2.0-84918826061 (Scopus ID)2bfd5cde-715d-4aab-b9f2-d582de42ab5f (Local ID)2bfd5cde-715d-4aab-b9f2-d582de42ab5f (Archive number)2bfd5cde-715d-4aab-b9f2-d582de42ab5f (OAI)
Note
Validerad; 2015; Nivå 2; 20141120 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gaddam, R., Pederson, R., Hörnqvist, M. & Antti, M.-L. (2014). Fatigue crack growth behaviour of forged Ti-6Al-4V in gaseous hydrogen (ed.). Paper presented at . Corrosion Science, 78, 378-383
Open this publication in new window or tab >>Fatigue crack growth behaviour of forged Ti-6Al-4V in gaseous hydrogen
2014 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 78, p. 378-383Article in journal (Refereed) Published
Abstract [en]

Fatigue crack growth (FCG) tests were performed to evaluate the fatigue behaviour of forged Ti-6Al-4V in air and high-pressure gaseous hydrogen (15 MPa) at room temperature. The results indicate that the effect of gaseous hydrogen is dependent on the stress intensity factor (ΔK). The FCG rate was unaffected by hydrogen below a critical stress intensity, ΔK* ≈ 20 MPa√m. Above ΔK*, the FCG rate fluctuated and subsequently accelerated at higher ΔK values. The observed behaviour is attributed to the change in the fracture processes. A hypothesis is proposed that describes the FCG behaviour in gaseous hydrogen.

Keywords
titanium, SEM, hydrogen embrittlement, Materials science - Construction materials, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-3036 (URN)10.1016/j.corsci.2013.08.009 (DOI)000329420900042 ()2-s2.0-84888007730 (Scopus ID)0ca240e9-a7f9-4ea3-a4e8-2917d631aade (Local ID)0ca240e9-a7f9-4ea3-a4e8-2917d631aade (Archive number)0ca240e9-a7f9-4ea3-a4e8-2917d631aade (OAI)
Note
Validerad; 2014; 20130818 (raggad)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gaddam, R., Antti, M.-L. & Pederson, R. (2014). Influence of alpha–case layer on the low cycle fatigue properties of Ti–6Al–2Sn–4Zr–2Mo alloy (ed.). Paper presented at . Materials Science & Engineering: A, 599, 51-56
Open this publication in new window or tab >>Influence of alpha–case layer on the low cycle fatigue properties of Ti–6Al–2Sn–4Zr–2Mo alloy
2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 599, p. 51-56Article in journal (Refereed) Published
Abstract [en]

Strain–controlled low cycle fatigue properties of Ti–6Al–2Sn–4Zr–2Mo with different thickness of alpha–case layers were investigated. Results show that at strain amplitudes 0.3 and 0.4%, the fatigue life of the alloy is reduced for the specimens with alpha–case layer compared to the ones without any alpha–case. It was noted that with a 2 μm thick alpha–case layer the low cycle fatigue life is reduced about 50% at the higher strain amplitude. The degrading effect of the alpha–case layer on fatigue life increased with increasing thickness. The alpha–case layer at the surface is enriched with oxygen making the surface harder and brittle, which results in easier crack initiation and thus decrease in fatigue life.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-3224 (URN)10.1016/j.msea.2014.01.059 (DOI)000334004400009 ()2-s2.0-84893768179 (Scopus ID)1055bd6d-5071-48cc-b780-8e6d6f2b425c (Local ID)1055bd6d-5071-48cc-b780-8e6d6f2b425c (Archive number)1055bd6d-5071-48cc-b780-8e6d6f2b425c (OAI)
Note
Validerad; 2014; 20140204 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gaddam, R., Hörnqvist, M., Antti, M.-L. & Pederson, R. (2014). Influence of High-pressure gaseous Hydrogen on the low-cycle fatigue and fatigue crack growth properties of a cast titanium alloy (ed.). Paper presented at . Materials Science & Engineering: A, 612, 354-362
Open this publication in new window or tab >>Influence of High-pressure gaseous Hydrogen on the low-cycle fatigue and fatigue crack growth properties of a cast titanium alloy
2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 612, p. 354-362Article in journal (Refereed) Published
Abstract [en]

In the present study, the effect of gaseous hydrogen on the fatigue properties of a commonly used aerospace titanium alloy (Ti–6Al–4 V) was studied. The low-cycle fatigue and fatigue crack growth properties were investigated at room temperature in ambient air and 15 MPa gaseous hydrogen. Results showed that the low-cycle fatigue life was significantly reduced in hydrogen, and the detrimental effect was larger at higher strain amplitudes. The fatigue crack growth rate in hydrogen remained unaffected below a critical stress intensity ΔK⁎≈17 MPa√m, while beyond this value, the fatigue crack growth rate fluctuated and increased with increasing ΔK. Fractography analysis clearly showed that gaseous hydrogen mainly affected the fatigue crack growth rate. On the fracture surfaces, striations were noted over the entire crack growth region in air, whereas in hydrogen striations were noted at stress intensities lower than ΔK⁎. Above ΔK⁎, secondary cracks and brittle flat surfaces with features similar to crack arrest marks were mostly observed in hydrogen. Microstructural analysis along the crack growth direction showed that the crack followed a transgranular path in air, i.e. through α colonies. In hydrogen, the crack also grew along the prior β grain boundaries and at α/β interface within the α colonies. Thereby, the detrimental effect of hydrogen in cast titanium alloy was attributed to a change in the fracture process during crack propagation

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-4183 (URN)10.1016/j.msea.2014.06.060 (DOI)000340331300044 ()2-s2.0-84903827773 (Scopus ID)21647969-6c43-40d9-8e8b-c418aa1f7c72 (Local ID)21647969-6c43-40d9-8e8b-c418aa1f7c72 (Archive number)21647969-6c43-40d9-8e8b-c418aa1f7c72 (OAI)
Note
Validerad; 2014; 20140625 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Sefer, B., Gaddam, R., Pederson, R. & Antti, M.-L. (2014). Study of the Alpha-Case Layer in Ti–6Al–2Sn–4Zr–2Mo and Ti–6Al–4V by Electron Probe Micro Analysis (ed.). Paper presented at Materials Science and Engineering Congress : MSE 2014 23/09/2014 - 25/09/2014. Paper presented at Materials Science and Engineering Congress : MSE 2014 23/09/2014 - 25/09/2014.
Open this publication in new window or tab >>Study of the Alpha-Case Layer in Ti–6Al–2Sn–4Zr–2Mo and Ti–6Al–4V by Electron Probe Micro Analysis
2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Titanium and its alloys are susceptible to oxidation when exposed to elevated temperatures and oxygen containing environments for long exposure times, e.g. in jet engines [1–3]. In such conditions oxygen rapidly reacts with titanium, stabilizing α–titanium and forming solid solution due to the high solubility of oxygen in titanium (14.5 wt.%) [4]. The oxidation results in simultaneous formation of oxide scale on top of the metal and a brittle oxygen enriched layer beneath the scale, commonly referred as alpha–case. Alpha–case layer reduces important mechanical properties such as ductility, fracture toughness, and most severe reduces the fatigue life of jet engine components when subjected to dynamical loadings [5]. Therefore, the alpha-case layer in aerospace applications is usually removed by chemical milling [1–3] or prevented by using vacuum environments and high temperature coatings [1–3,6–9]. In the present study alpha–case in Ti–6Al–2Sn–4Zr–2Mo and Ti–6Al–4V alloys was developed by performing isothermal heat treatments at 700 °C in ambient air for 500 hours. The developed alpha–case layer was evaluated metallographically and by using instrumental techniques. It was found that the alpha–case development is a function of alloy composition and microstructure. The oxygen and the main alloying elements concentration profiles were measured using Electron Probe Micro Analyzer (EPMA) in both alloys. Based on the analysis of the concentration profiles an increase of the amount of alpha phase in the two alloys was found as a result of beta to alpha phase transformation.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-30019 (URN)3af2d3e5-da1d-40f4-9b0e-8da7f6e8a854 (Local ID)3af2d3e5-da1d-40f4-9b0e-8da7f6e8a854 (Archive number)3af2d3e5-da1d-40f4-9b0e-8da7f6e8a854 (OAI)
Conference
Materials Science and Engineering Congress : MSE 2014 23/09/2014 - 25/09/2014
Note
Godkänd; 2014; 20141124 (birsef)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-08Bibliographically approved
Gaddam, R., Pederson, R., Hörnqvist, M. & Antti, M.-L. (2013). Influence of hydrogen environment on fatigue crack growth in forged Ti-6Al-4V: fractographic analysis (ed.). In: (Ed.), (Ed.), 7th EEIGM International Conference on Advanced Materials Research: 21–22 March 2013, LTU, Luleå, Sweden. Paper presented at EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013. : IOP Publishing Ltd, Article ID 1210.
Open this publication in new window or tab >>Influence of hydrogen environment on fatigue crack growth in forged Ti-6Al-4V: fractographic analysis
2013 (English)In: 7th EEIGM International Conference on Advanced Materials Research: 21–22 March 2013, LTU, Luleå, Sweden, IOP Publishing Ltd , 2013, article id 1210Conference paper, Published paper (Refereed)
Abstract [en]

In this study, the influence of hydrogen environment (15 MPa) on the fatigue crack growth in forged Ti-6A1-4V at room temperature is investigated. It is observed that at 21 < ΔK > 25 MPa√m, there exists a change of fatigue crack growth rate (FCGR) in hydrogen environment, and it is accelerated at ΔK > 25MPa√m. FCGR in hydrogen environment is dependent on the stress intensity levels (ΔK). Detailed fractographic analysis of the fracture surfaces were performed at different ΔK using high-resolution scanning electron microscope (HR-SEM). Fatigue striations were observed in air and hydrogen at ΔK < 21MPa√m. At ΔK > 21MPa√m, secondary cracks were observed in hydrogen environment. The differences in appearances of fracture surfaces in air and hydrogen are discussed.

Place, publisher, year, edition, pages
IOP Publishing Ltd, 2013
Series
I O P Conference Series: Materials Science and Engineering, ISSN 1757-8981 ; 1
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-27795 (URN)10.1088/1757-899X/48/1/012010 (DOI)000329228200010 ()2-s2.0-84893623239 (Scopus ID)157fe2dc-2632-4c3e-b258-0d8be050749a (Local ID)157fe2dc-2632-4c3e-b258-0d8be050749a (Archive number)157fe2dc-2632-4c3e-b258-0d8be050749a (OAI)
Conference
EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013
Note
Validerad; 2013; 20130926 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Gaddam, R. (2013). Microstructure and mechanical properties of Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V: influence of H, O and B (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Microstructure and mechanical properties of Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V: influence of H, O and B
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Titanium and its alloys are used in a wide range of applications from aerospace, marine, biomedical implants and consumer goods, due to their superior specific strength, excellent corrosion resistance, and biocompatibility. In aerospace applications, these alloys are predominately used as components in the aero/rocket engines because of their high strength-to-density ratio compared to other metallic materials. Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) and Ti-6Al-4V (Ti-64) are the two most commonly used alloys in aeroengines where the temperature reaches up to 300-450°C. Ti-6242 is preferred for higher temperature applications i.e. up to 450°C, owing to their excellent fatigue and creep resistance at elevated temperature. Ti-64 is used up to 300°C because of its good tensile and fatigue strength. In titanium alloys, the mechanical properties are dependent on variables such as, alloy chemistry, manufacturing methods and environmental conditions during the service. These variables greatly influence the microstructure, which inherently affects their properties. The focus of the present research work is to understand the influence of specific elements such as hydrogen, oxygen and boron on the mechanical properties of Ti-6242 and Ti-64 alloys. In the first study, Ti-64 alloy has been exposed to gaseous hydrogen (15 MPa). Here the tensile, low cycle fatigue (LCF) and fatigue crack growth (FCG) properties were explored. Studies showed that in gaseous hydrogen, the LCF life and the FCG resistance were significantly reduced in comparison to those properties measured in ambient air. However, it was observed that there was no significant influence of gaseous hydrogen on the ductility. The influence of hydrogen on the mechanical properties seems to be dependent on the microstructure of the alloy. It was noted that the yield strength (YS), ultimate tensile strength (UTS) and LCF life in gaseous hydrogen were higher for Ti-64 alloy with smaller prior beta grains and smaller alpha colonies than compared to the coarse microstructure. Similar observation was also noted for the FCG resistance. The results in the study indicate that hydrogen mainly influences the crack growth properties, as it changes the mode of fracture from ductile to brittle at a critical stress intensity value. Secondly, Ti-6242 alloy was isothermally heat-treated in ambient air at the temperatures 500, 593 and 700°C up to 500 hours. At these temperatures and times, it was noted that a brittle layer that is enriched with oxygen was formed. This layer is termed “alpha-case”. The thickness of this layer increased with temperature and exposure time. To investigate the effect of this layer on the mechanical properties, LCF testing at strain amplitudes 0.3 and 0.4% was performed for different alpha-case thicknesses. It was noted that the LCF life reduced about 50% with 2 μm thick alpha-case and about 90% with 10 μm thickness at strain amplitudes 0.4%. The study also indicated that the life for fatigue crack initiation is affected rather than the fatigue crack propagation, and the reduction in LCF life is because of the layer enriched with oxygen.Finally, the influence of boron on the compression, tensile and LCF properties of Ti-64 alloy were investigated. Here small amount of boron (i.e. 0.06 and 0.11 wt.%) was added during casting of Ti-64 alloy. It was noted that the boron refined the coarse “as cast” microstructure by precipitating TiB precipitates along the grain boundaries. The refined microstructure increased the compressive strength, YS, UTS and ductility at room temperature. The LCF life of cast Ti-64 alloy with boron up to 0.11 wt.% was increased at strain amplitudes ≤ 0.75%. At higher strain amplitudes (1%), the LCF life was reduced . It is because of cracking of the TiB precipitates, which can easily initiate the cracks. Beside this, it was noted that the effect of grain refinement is diminishing at the temperatures above 500°C. The study showed that the increase in mechanical properties of Ti-64 alloys with boron is a result of reduction in both the prior beta grain and alpha colony dimensions.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Titanium alloys, Hydrogen, Oxygen, Boron, Tensile, Compression, Fatigue, Metallography, Fractography, Materials science - Construction materials, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-26338 (URN)dcb96bba-6472-47df-9633-930e376dfefa (Local ID)978-91-7439-732-1 (ISBN)978-91-7439-733-8 (ISBN)dcb96bba-6472-47df-9633-930e376dfefa (Archive number)dcb96bba-6472-47df-9633-930e376dfefa (OAI)
Note
Godkänd; 2013; 20130902 (raggad); Tillkännagivande disputation 2013-10-03 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Raghuveer Gaddam Ämne: Konstruktionsmaterial/Engineering Materials Avhandling: Microstructure and Mechanical Properties of Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V: Influence of H, O and B Opponent: Dr Senior Lecturer Barbara Shollock, Dept of Materials, Imperial College, London, UK Ordförande: Docent Marta-Lena Antti, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 24 oktober 2013, kl 10.15 Plats: E632, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-08Bibliographically approved
Singha, G., Gaddam, R., Petley, V., Datta, R., Pederson, R. & Ramamurtya, U. (2013). Strain-controlled fatigue in B-modified Ti-6Al-4V alloys (ed.). Paper presented at . Scripta Materialia, 69(9), 698-701
Open this publication in new window or tab >>Strain-controlled fatigue in B-modified Ti-6Al-4V alloys
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2013 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 69, no 9, p. 698-701Article in journal (Refereed) Published
Abstract [en]

The strain-controlled fatigue behaviour of Ti-6Al-4V alloy with up to 0.11 wt.% B addition was investigated. Results show significant softening when the strain amplitudes, ΔεT/2, are ⩾0.75%. B addition was found to improve the fatigue life for ΔεT/2 ⩽ 0.75% as it corresponds to the elastic regime and hence strength dominated. At ΔεT/2 = 1%, in contrast, the base alloy exhibits higher life as TiB particle cracking due to strain incompatibility renders easy crack nucleation in the B-modified alloys.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-2400 (URN)10.1016/j.scriptamat.2013.08.008 (DOI)000325194500014 ()2-s2.0-84884286655 (Scopus ID)00499127-d967-4e58-957f-bc8a71182cdf (Local ID)00499127-d967-4e58-957f-bc8a71182cdf (Archive number)00499127-d967-4e58-957f-bc8a71182cdf (OAI)
Note
Validerad; 2013; 20130816 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Gaddam, R., Sefer, B., Pederson, R. & Antti, M.-L. (2013). Study of alpha case depth in Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V (ed.). In: (Ed.), (Ed.), 7th EEIGM International Conference on Advanced Materials Research: 21–22 March 2013, LTU, Luleå, Sweden. Paper presented at EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013. : IOP Publishing Ltd, Article ID 12002.
Open this publication in new window or tab >>Study of alpha case depth in Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V
2013 (English)In: 7th EEIGM International Conference on Advanced Materials Research: 21–22 March 2013, LTU, Luleå, Sweden, IOP Publishing Ltd , 2013, article id 12002Conference paper, Published paper (Refereed)
Abstract [en]

Titanium alloys, mostly Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) and Ti-6Al-4V (Ti-64) are used in aero engine applications, because they possess high specific strength. The future concept in designing aircraft engines results in higher pressure, which increases the efficiency of aircraft engines by achieving high thrust and lowering the fuel consumption. Nevertheless, higher pressure in the engine means increase of service temperature. These conditions enforce new requirements on the materials used for manufacturing the engine components (compressors). Ti-6242 is mostly used in compressors where the service temperature is in the range of 400-450°C. It is well known that titanium alloys above 480°C for longer service time have tendency to form a hard and brittle oxygen stabilized surface layer (α-case). This layer has impact on the mechanical properties of the surface, by lowering the tensile ductility and the fatigue resistance. Factors that contribute for growth of α-case are: presence of oxygen, exposure time, temperature and pressure. In order to extend the service temperature of titanium alloys, it is required to understand the formation of α-case at high temperatures for long exposure times. In the present study, isothermal oxidation experiments in air were performed on forged Ti-6242 alloy at 500°C and 593°C up to 500 hours. Similar studies were also performed on Ti-64 sheet at 593°C and 700°C. Alpha case depths for both alloys were quantified using metallography techniques and compared.

Place, publisher, year, edition, pages
IOP Publishing Ltd, 2013
Series
I O P Conference Series: Materials Science and Engineering, ISSN 1757-8981 ; 1
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-38664 (URN)10.1088/1757-899X/48/1/012002 (DOI)000329228200002 ()2-s2.0-84893552336 (Scopus ID)d1d7731f-17be-4df5-bced-73461fcdbedf (Local ID)d1d7731f-17be-4df5-bced-73461fcdbedf (Archive number)d1d7731f-17be-4df5-bced-73461fcdbedf (OAI)
Conference
EEIGM International Conference on Advanced materials research : 21/03/2013 - 22/03/2013
Note
Validerad; 2013; 20130818 (raggad)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-07-10Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6613-7876

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