Hot corrosion in gas turbine components

Eliaz, Noam; Shemesh, G.; Latanision, R. M.

doi:10.1016/s1350-6307(00)00035-2

Cited by 573 publications

(258 citation statements)

References 35 publications

Supporting

Mentioning

235

Contrasting

Unclassified

Order By: Relevance

“…Hot corrosion can be defined as accelerated corrosion that results from the presence of salt contaminants such as Na 2 SO 4 , NaCl and V 2 O 5 which form molten deposits that react with the protective oxide coatings [7,8]. Laser-glazing has been mentioned by Jones [3] and Gurrappa [6], as an approach to improve the hot corrosion resistance of zirconia-based thermal barrier coatings by preventing salt penetration into the coating.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of laser-glazed plasma-sprayed thermal barrier coatings under high temperature exposure to molten salts

Batista

Portinha

Ribeiro

et al. 2006

Surface and Coatings Technology

125

View full text Add to dashboard Cite

Thermal Barrier Coating (TBC) systems are frequently used in gas turbine engines to provide thermal insulation to the hot-section metallic components and also to protect them from oxidation, hot corrosion and erosion. Surface sealing treatments, namely laser-glazing, have been showing a high potential for extending in-service lifetimes of these systems by improving chemical and thermo-mechanical resistance. In this investigation, both as-sprayed and laserglazed TBCs were exposed to hot corrosion in molten salts. The glazed coatings were obtained by scanning the surface of the plasma-sprayed coatings with either a CO 2 or a Nd:YAG laser.The hot corrosion investigation was accomplished by subjecting the specimens to an isothermal air furnace testing under V 2 O 5 and/or Na 2 SO 4 in a temperature of 1000ºC for 100 hours.Spallation has been observed in coatings in the as-sprayed condition under V 2 O 5 or -2 -V 2 O 5 +Na 2 SO 4 . Na 2 SO 4 itself had no or minimal effect on the degradation of the laser-glazed or as-sprayed condition coatings, respectively. The degradation in V 2 O 5 was accomplished by destabilization of YSZ as a consequence of depletion of yttria from the solid solution to form YVO 4 and therefore led to the disruptive transformation of the metastable tetragonal phase to the monoclinic phase. Moreover, the presence of both corrosive salts induced the formation of large high aspect ratio YVO 4 crystals that introduced additional stresses and contributed to the degradation of the coatings. The laser-glazed specimens were not efficient in avoiding the molten salt penetration along the thickness direction due to the presence of cracks on the glazed layer.However due to a reduced specific surface area of the dense glazed layer, the corrosion reaction of the molten salts with the YSZ has been lower than in coatings in the as-sprayed condition.-3 -

show abstract

Section: Introductionmentioning

confidence: 99%

Evaluation of laser-glazed plasma-sprayed thermal barrier coatings under high temperature exposure to molten salts

Batista

Portinha

Ribeiro

et al. 2006

Surface and Coatings Technology

125

View full text Add to dashboard Cite

show abstract

“…This is a major concern due to the role of SO 3 in sulfuric acid corrosion and low temperature hot corrosion [58][59][60]. The formation of SO 3 has been predicted to be increased in oxy-coal combustion compared to air combustion [61], mainly because SO 2 is recycled with the flue gas, thus leading to a higher sulfur concentration.…”

Section: Validation: H 2 S Oxidationmentioning

confidence: 99%

Chemical kinetics mechanism for oxy-fuel combustion of mixtures of hydrogen sulfide and methane

Bongartz

Ghoniem

2015

Combustion and Flame

View full text Add to dashboard Cite

Oxy-fuel combustion of sour gas, a mixture of natural gas (essentially methane (CH 4 )), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S), could enable the utilization of large natural gas resources, especially when combined with enhanced oil recovery. In this work, a detailed chemical reaction mechanism for oxy-fuel combustion of sour gas is presented. To construct the mechanism, a CH 4 sub-mechanism was chosen based on a comparative validation study for oxy-fuel combustion. This mechanism was combined with a mechanism for H 2 S oxidation, and the sulfur sub-mechanism was then optimized to give better agreement with relevant experiments. The optimization targets included predictions for the laminar burning velocity, ignition delay time, and pyrolysis of H 2 S, and H 2 S oxidation in a flow reactor. The rate parameters of 15 sulfur reactions were varied in the optimization within their respective uncertainties. The optimized combined mechanism was validated against a larger set of experimental data over a wide range of conditions for oxidation of H 2 S and interactions between carbon and sulfur species. Improved overall agreement was achieved through the optimization and all important trends were captured in the modeling results. The optimized mechanism can be used to make qualitative and some quantitative predictions on the combustion behavior of sour gas. The remaining discrepancies highlight the current uncertainties in sulfur chemistry and underline the need for more accurate direct determination of several important rate constants as well as more validation data.

show abstract

“…It is generally thought that to combat hot corrosion/sulphidation, a cobalt based coating is better. This basically stems from the fact that at high temperatures cobalt base alloys have a better resistance to sulphidation than Ni-based alloys [5] which could be attributed to the fact that the diffusivity of sulphur in cobalt base alloys is approximately 100 times lower than in Ni-based alloys [51] . Some papers state that better hot corrosion resistance is seen from MCrAlY coatings with larger cobalt additions present [8] [52] .…”

Section: Cobaltmentioning

confidence: 99%

“…However, as has been previously mentioned the effect of sulphur on the oxide scale is well known with respect to how it can detrimentally affect the adherence of a scale. Therefore, it is interesting to note that the diffusivity of sulphur in a cobalt base alloy is substantially lower than that in a Nibased alloy [51] . This would therefore suggest that the sulphur in a CoNiCrAlY coating will diffuse towards the metal-scale interface at a much lower rate than in a NiCrAlY coating therefore lowering the chance of void formation at the metal-scale interface thereby reducing adhesion.…”

Section: Figure 222mentioning

confidence: 99%

Oxidation of MCrAlY Coatings on Ni-Based Superalloys

Pace¹,

Thomson²,

Wells³

2008

Superalloys 2008 (Eleventh International Symposium)

View full text Add to dashboard Cite

i AcknowledgementsFirstly I would like to thank the Department of Materials for the use of their materials and facilities. The range of equipment available and people have made working there a pleasure, but also allowed the use of several techniques that proved invaluable.I am grateful to my project supervisor, Professor R. C. Thomson; firstly for offering me such an interesting project and secondly, for her guidance and support, which have been invaluable during this project.I would also like to thank Dr G. West for the continued support he has given me throughout my PhD. His help and guidance on many aspects (especially on FIBSEM and TEM related matters) have been immeasurable, but more than that I am extremely grateful for his moral support and his friendship; working with him is something I will miss. I would also like to thank my fellow office mates, especially Juan Sanchez-Hanton and Kate Burke for helping to create such an enjoyable office atmosphere.I am also extremely grateful to RWE npower for part funding this project and giving me the opportunity to look at such an interesting area of metallurgy. I am especially grateful to Dr Jon Wells from RWE npower, not only for providing a raft of samples but for his advice and support throughout.Finally, I would like to thank my friends and family for their support and encouragement throughout, especially my parents for having always been there to offer help and support, and Anne for always cheering me up and supporting me through the difficult times.ii AbstractEnsuring a sustainable power generation supply into the future is of worldwide importance. A combination of power generation methods to meet this (including both fossil plant and renewables) is a certainty. Therefore, the maintenance of conventional fossil-fired plants is required to provide a low cost, flexible and reliable electricity supply, and in order to conserve fuel resources it is important to ensure they operate as efficiently as possible. Lifetime predictions of important components (such as turbine blades in industrial gas turbine engines) are essential in order to avoid failures and unnecessary downtime, improve the ability to schedule routine maintenance work and to help develop new coating systems to meet the ever more demanding requirements. Better models would allow improved predictions and mean that service schedules could be set with better accuracy thereby, limiting downtime and reducing costs as well as being better able to predict coating performance and thus increase engine efficiency.Ni-based superalloys are a common material utilised for turbine blades due to their high temperature strength. Coupled with MCrAlY coating systems and thermal barrier coatings (TBC) they are able to withstand both the high temperatures and arduous environments they will encounter during service. In order to effectively predict the lifetime of components such as turbine blades it is vital to understand the oxidation behaviour of these systems and how factors such as the MCrAlY composition, processing f...

show abstract

Hot corrosion in gas turbine components

Cited by 573 publications

References 35 publications

Evaluation of laser-glazed plasma-sprayed thermal barrier coatings under high temperature exposure to molten salts

Evaluation of laser-glazed plasma-sprayed thermal barrier coatings under high temperature exposure to molten salts

Chemical kinetics mechanism for oxy-fuel combustion of mixtures of hydrogen sulfide and methane

Oxidation of MCrAlY Coatings on Ni-Based Superalloys

Contact Info

Product

Resources

About