Engineering Failure Analysis 70 (2016) 419–427

Contents lists available at ScienceDirect

Engineering Failure Analysis

j ourna l homepage: www.e lsev ie r .com/ locate /engfa i lana l

Failure analysis of a fluidisation nozzle in biomass boiler and thelong-term high temperatures oxidation behaviour of 304stainless steel

William LiuIndustrial Services (NDT & Materials), SGS New Zealand Ltd., Auckland, New Zealand

a r t i c l e i n f o

E-mail address: William.liu@sgs.com.

http://dx.doi.org/10.1016/j.engfailanal.2016.10.0011350-6307/© 2016 Elsevier Ltd. All rights reserved.

a b s t r a c t

Article history:Received 21 July 2016Received in revised form 5 October 2016Accepted 5 October 2016Available online 06 October 2016

The long-term (N10 years) oxidation behaviour of stainless steels (SS) at high temperatureswas previously unknown. The behaviour was studied through a case study of failure analysis.A fluidisation nozzle made of 304 austenitic SS. After over 100,000 h of service at temperaturesof 790–820 °C in a biomass boiler, the nozzle fractured. Failure analysis pinpoints that the noz-zle wall temperature fluctuation caused the oxide scale cracking, which intensified the oxida-tion. The brittle fracture was due to fully oxidization.The long-term oxidation behaviours are distinct from the short-term oxidation behaviours.XRD analysis indicates that the scale was mainly Fe+2Cr2O4 and (Fe0.6 Cr0.4)2O3. ESEM/EDSanalysis indicates internal oxidation and sulfidation along the grain boundaries. The differentdiffusion rates of the Fe, Cr and Ni atoms formed a Ni-rich (48%) layer underneath the scale,and a Cr-rich (35%) core in the remained SS. A schematic is proposed to describe the diffusionmechanism of the internal oxidization and sulfidation behaviour.

© 2016 Elsevier Ltd. All rights reserved.

Keywords:Stainless steelLong-term oxidationFe+2Cr2O4

Internal oxidationSulfidation

1. Introduction

With the application of stainless steels (SS) in high temperatures, SS oxidation behaviours warrant attention in the industry.For short-term oxidation behaviours, various types of stainless steels in different environments have been extensively studied,such as austenitic SS [1–14]; ferritic SS [14–18]; and duplex SS [19–23].

For long-term oxidation behaviours of the SS, however, very limited literature is available. Laboratory experiment at 650–800 °C in air up to 5000 h have been reported [24]. In field study, 304H at about 605 °C in service for 12,000 h and 34,696 hhad been investigated [25]. Despite the significance of long-term oxidation behaviours, it is far from understood. Due to thehigh cost of the long-term laboratorial experiments, no laboratory tests at high temperatures for over 10 years have been reportedso far. Therefore, field study from the industrial cases can provide the valuable specimens for the study of the long-term oxidationbehaviours [25].

In this article, through an industrial case study of nozzle failure analysis, the long-term oxidation behaviours of the austeniticSS had been studied. The findings from this case study are distinct from the short-term oxidation behaviours.

The fluidisation nozzles were located at the bottom of a biomass boiler. The function of the nozzle is to create a combustiongasification media for the biomass. The nozzle is welded to a fluidizing air pipe (Fig. 1). The fluidizing air pipes are connected tothe air manifold header. The air flows through the nozzle holes (Fig. 2) to fluidise the silica sand.

Fig. 1. The drawing of the fluidizing air pipes in a biomass boiler.

420 W. Liu / Engineering Failure Analysis 70 (2016) 419–427

The nozzles were made of austenitic SS grade 304. The temperature of the sand surrounding the nozzle was 790–820 °C, andthe air temperature flowing through the nozzles was 180–200 °C. It can be understood that a considerable temperature gradientexisted in the nozzle wall.

In 2015, a nozzle failure occurred. The nozzles had been operated for approximately 105,000 h since the boiler was commis-sioned in 2002. The nozzles were cut out for failure analysis. Ash blockage inside the nozzles was noted (Fig. 2). It had been di-agnosed by the client that the ash was introduced into from the air due to the boiler operational malfunction.

The long-term oxidation behaviour of SS over 100,000 h is unknown. This nozzle proved to be a valuable specimen for study-ing long-term oxidation behaviour.

2. Experimental methods

Fig. 2 compares the fractured nozzle with the none-fractured nozzle. In the fractured nozzle, three representative specimens(A, B and C) had been cut from the edge of fracture surface for various analyses with the following methods and techniques:

• Visual inspection.• SES (spark emission spectrometry) for steel chemical composition analysis. The model was Spectrotest TXC25.• Light Optical Microscopes (both stereomicroscopic and metallographic microscope). The metallographic specimens had beenmounted and polished and etched with 2% natal.

None-fractured Nozzle Fractured Nozzle

Specimens Cut from the Fracture Area

A

B

C

Ash Blockage

Nozzle Holes

Fig. 2. The sand air fluidisation nozzles cut from a biomass boiler (a none-fractured nozzle and a fractured nozzle).

Outer Oxide Scale

Inner Oxide Scale

Remaining SS

Specimen A Specimen B Specimen C

Fig. 3. The cross-sections of the three specimens under stereomicroscope: (a) Specimen A – after polishing and etching (10×); (b) Specimen B - the fracture surface(10×), showing the remaining SS decreasing; (c) Specimen C - the fracture surface (15×), showing the completely oxidized nozzle wall.

421W. Liu / Engineering Failure Analysis 70 (2016) 419–427

• XRD (X-ray diffraction) analysis for crystal structures of the corrosion products. The model was Bruker D2 Phaser. The diffrac-tion patterns were analysed by the software to match the peaks with the database in the instrument.

• ESEM/EDS (environmental scanning electron microscopy/energy-dispersive spectroscopy). The model was an FEI Quanta 200 Fwith field emission gun. The EDS (energy dispersive spectroscope) detector was EDAX brand SiLi (Lithium drifted) with a SuperUltra Thin Window. All the images in this article were backscattered electron images.

3. Analysis results

3.1. Visual and macro inspection

Visual inspection found that the failure mode was fracture due to the severe oxidation (Fig. 2). In the fracture area, the SS hadalmost fully been oxidized. The loss of strength due to the full oxidization resulted in brittle fracture.

Fig. 3 shows the macro images of the cross-section of each specimen, showing the oxidation deterioration.In Specimen A (Fig. 3a), the oxidation was at the moderate stage. SS remains at approximately 70% of the cross section.In Specimen B (Fig. 3b), the oxidation was at the severe stage. SS remains at less than half of the cross section. The remaining

SS decreased dramatically in the specimen.In Specimen C (Fig. 3c), the nozzle wall had been completely oxidized.The microstructures of the remained SS in Specimen A are shown in Fig. 4a. The coarse austenitic grains indicate grain growth

after long-term service at the high temperatures.

3.2. Steel chemical composition analysis

To confirm the steel grade, SES were applied on the nozzle bottom after the scale had been completely removed (Fig. 4b).Table 1 lists the main elements of the test results.

The results indicate that the steel grade was 304 L. However, as the decarburizing can occur during long-term service [26] andthe carbon content could be reduced, the original carbon content could not be determined from this sample.

Fig. 4. (a) The microstructures of the remained SS in Specimen A (200×); (b) The spark marks on the nozzle bottom for the SES test.

Table 1The chemical compositions of the nozzle steel.

Element (% W) C Si Mn P S Cr Ni Mo V Cu Fe

Nozzle Steel 0.03 0.48 1.15 0.01 0.03 18.46 8.65 0.17 0.026 0.034 Bal.304 0.08 b0.75 b2.0 b0.045 b0.03 18.00–20.00 8.00–10.00 Bal.304 L b0.03 b0.75 b2.0 b0.045 b0.03 18.00–20.00 8.00–10.00 Bal.

422 W. Liu / Engineering Failure Analysis 70 (2016) 419–427

3.3. XRD analysis

The nozzle oxide scales had been removed for XRD analysis. Fig. 5 shows the analysis results. There were mainly two types ofoxides, Fe+2Cr2O4 and (Fe0.6 Cr0.4)2O3.

The corundum-type (CrxFe1 − x)2O3 has been reported in laboratory test [27]. However, the Fe+2Cr2O4 (chromite) had notbeen reported in the short-term oxidation studies.

3.4. ESEM/EDS analysis

3.4.1. Specimen AFig. 6a shows Specimen A under ESEM at low magnification. Cracking between oxide scales and the remained SS is obvious,

particularly in the outer scale.A Ni-rich layer in each side has been identified. Fig. 6b displays the details of the Ni-rich layer in the inner side. The thickness

of the Ni-rich layer was 65 μm. In situ EDS1 analysis results on the Ni-rich layer are shown in Fig. 7a. The nickel content increasedto 48.1%, while the chromium content reduced to 11.7%.

In the Ni-rich layer, substantial internal oxidation along the grain boundaries was observed. This internal oxidation alsooccurred in the remaining SS. EDS2 analysis results on the corrosion products are shown in Fig. 7b. Considerable amount of sulfurin the corrosion products indicates the involvement of sulfidation in the oxidation process.

EDS analyses had also been conducted on the remaining SS and the scale respectively. Fig. 8a shows EDS3 analysis results onthe remaining SS. The chromium and nickel contents are very close to Grade 304, indicating no substantial diffusion of the chro-mium and nickel at this oxidation stage. Trace amounts of oxygen had been detected, confirming the internal oxidation in the re-maining SS during long-term service.

00-034-0412 (I) - Iron Chromium Oxide - (Fe0.6Cr0.4)2O3 - Y: 48.04 % - d x by: 1. - WL: 1.5406 - Rhombo.H.axes - a 5.01700 - b 5.01700 - c 13.64300 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primitive - R (0)00-034-0140 (*) - Chromite, syn - Fe+2Cr2O4 - Y: 92.15 % - d x by: 1. - WL: 1.5406 - Cubic - a 8.37900 - b 8.37900 - c 8.37900 - alpha 90.000 - beta 90.000 - gamma 90.000 - Face-centered - Fd-3m (227) - 8 - 588.27Operations: Background 1.000,1.000 | ImportFile: iron oxide.raw - Type: Locked Coupled - Start: 10.000 ° - End: 80.009 ° - Step: 0.020 ° - Step time: 38.4 s - Temp.: 25 °C (Room) - Time Started: 0 s - 2-Theta: 10.000 ° - Theta: 5.000 ° - Chi: 0.00 ° - Phi: 0.00 ° -

Lin

(C

ounts

)

0

100

200

300

400

500

600

700

800

900

2-Theta - Scale11 20 30 40 50 60 70

Fe+2Cr2O4

(Fe0.6 Cr0.4)2O3

Fig. 5. The XRD analysis results on oxide scales.

Fig. 6. Specimen A under ESEM: (a) at low magnification (70×); (b) The Ni-rich layer in the inner side (ESEM 1000×).

423W. Liu / Engineering Failure Analysis 70 (2016) 419–427

EDS4 analysis results on the scale are shown in Fig. 8b, indicating the significant amount of oxygen and the decrease in chro-mium content.

3.4.2. Specimen BFig. 9a shows the fracture surface of Specimen B at low magnification. The cracks between outer side scale and the remaining

SS also been identified.Fig. 9b is the analysis results of EDS1 on the remaining SS. Trace amount of oxygen and sulfur indicates the minor internal

oxidation and sulfidation. However, the Cr-rich (34.8%) and Ni-depletion (5.7%) indicate alloy element diffusion in the long-term process.

Fig. 10 is the EDS analysis results on the scales of both sides respectively. However, the nickel content in outer scale was muchhigher than that in inner scale, indicating the outward diffusion of nickel. Trace amount of sulfur had been detected, furtherconfirming the involvement of sulfidation in the oxidation process.

3.4.3. Specimen CFig. 11a shows the fracture surface of Specimen C under ESEM at low magnification. The layer feature in the oxide scale was

discerned.In situ EDS analysis results on the selected area are shown in Fig. 11b. Considerable amount of sulfur in the scale indicates the

substantial sulfidation involvement.

Element Wt % At %

O K 2.76 8.85SiK 1.04 1.89S K 3.41 5.45K K 0.04 0.06CaK 0.11 0.15CrK 11.7 11.52MnK 1.44 1.34FeK 31.33 28.73NiK 48.16 42.02

Total 100 100

Element Wt % At %

O K 11.98 29.38SiK 3.14 4.38S K 8.79 10.76K K 0.08 0.08CaK 0.16 0.16CrK 40.4 30.5MnK 8.48 6.06FeK 19.15 13.46NiK 7.82 5.23

Total 100 100

Fig. 7. The EDS analysis results: (a) EDS1 on Ni-rich layer; (b) EDS2 on the corrosion products in the grain boundaries.

Element Wt % At %

O K 1.59 5.24SiK 0.62 1.16S K 0.4 0.66K K 0.04 0.05CaK 0.13 0.17CrK 18.35 18.61MnK 1.92 1.84FeK 68.27 64.46NiK 8.69 7.81

Total 100 100

Element Wt % At %

O K 15.22 38.05SiK 1.02 1.45K K 0.24 0.24CaK 0.28 0.28CrK 11.58 8.91MnK 1.26 0.91FeK 62.1 44.48NiK 8.3 5.66

Total 100 100

Fig. 8. The EDS analysis results: (a) EDS3 on the remained SS; (b) EDS4 on the scale.

424 W. Liu / Engineering Failure Analysis 70 (2016) 419–427

The cracking from outer surface was observed. Fig. 12a shows the detail features of the cracks. At higher magnification(Fig. 12b), it can be distinguished that the metal sulfides had molten, leaving the voids.

4. Discussion

4.1. The root cause of nozzle failure

In nonfluctuating-temperature condition, cracking in the SS scale would not be likely. However, in the fluctuating-temperaturecondition, the expansion coefficient difference between the scale and SS would cause the cracking.

In the initial stage of the ash blockage due to boiler operational malfunction, the temperature gradient in the nozzle wallwould vary significantly with the unstable air flow. The continuous intermittent ash blockage would cause the scale cracking.

The cracking provides a pathway for the oxygen to intensify oxidation of the remaining SS. In the case of the chronic blockage,the temperatures of the whole nozzle wall would reach the ambient temperature (790–820 °C); significantly accelerating the ox-idation process. Eventually, the nozzle wall had been completely oxidized. The layer features in Specimen C (Fig. 11a) could asso-ciate with the fluctuating-temperatures. Therefore, the ash blockage was the root cause of the nozzle failure.

Element Wt % At %

O K 1.23 4.02AlK 0.25 0.49SiK 0.6 1.12S K 0.51 0.83CaK 0.39 0.51CrK 34.83 35.02MnK 2.32 2.21FeK 54.21 50.76NiK 5.66 5.04

Total 100 100

Fig. 9. (a) The fracture surface of Specimen B under ESEM (56×); (b) The analysis results of EDS1 on the remained SS.

Element Wt % At %

O K 14.92 35.97NaK 1.73 2.9AlK 0.52 0.74SiK 2.14 2.94S K 1.74 2.09K K 0.76 0.75CaK 0.33 0.32CrK 11.01 8.17MnK 3.21 2.25FeK 61.5 42.47NiK 2.13 1.4

Total 100 100

Element Wt % At %

O K 12.46 32.01NaK 0.8 1.43AlK 0.45 0.68SiK 1.35 1.98S K 0.89 1.14K K 0.27 0.28CaK 1.19 1.22CrK 15.03 11.88MnK 1.76 1.32FeK 55.7 40.99NiK 10.09 7.07

Total 100 100

Fig. 10. EDS analysis results on oxide scales: (a) EDS2 on the inner oxide scale; (b) EDS3 on the outer oxide scale.

425W. Liu / Engineering Failure Analysis 70 (2016) 419–427

4.2. The sulfidation

The flue gas of the biomass boiler contained sulfur compounds; either sulfur dioxide or hydrogen sulphide depending on ox-idation/reducing conditions during combustion. Hence, the involvement of sulfidation in the corrosion process was certain.

According to the binary phase diagrams [28], the eutectic temperature of Ni-S is approximately 620 °C, and the eutectic tem-perature of Fe-S is 988 °C. The eutectic temperatures of multi-elements would further reduce. The molten feature (Fig. 12b) indi-cates that the eutectic temperature of the metal sulfides in this case study was lower than the ambient temperature (790–820 °C).The melting of the metal sulfides formed the voids, in which the diffusion process would be enhanced.

4.3. The long-term oxidation behaviour

In the short-term oxidation behaviour, the outward diffusion of Fe ion formed (CrxFe1 − x)2O3 scale [1,4,27]. A very think(3 μm) Ni-rich metallic particles under the (Fe,Cr)3O4 outer scale had been reported [1]. It was explained as the diffusion of Feions through Cr2O3 was faster than Cr ions, leaving the Ni-rich particles.

Distinct from the short-term oxidation behaviour, the long-term outward diffusions of both Fe and Cr formed the oxide scalecomposed of Fe+2Cr2O4 in addition to (Fe0.6 Cr0.4)2O3 in this case study. This diffusion mechanism can be schematically described

EDS

Element Wt % At %

O K 13.16 33.46SiK 0.87 1.26S K 3.53 4.48CrK 21.48 16.81MnK 1.86 1.38FeK 46.86 34.13NiK 12.24 8.48

Total 100 100

Fig. 11. (a) The fracture surface of Specimen C under ESEM (55×); (b) The EDS analysis results on the scale.

Fig. 12. (a) the cracking feature of Specimen C (250×); (b) the molten features of the metal sulfides in the oxide scale (1000×).

426 W. Liu / Engineering Failure Analysis 70 (2016) 419–427

in Fig. 13. In the moderate oxidation stage, a Ni-rich (48%) layer up to 65 μm formed due to the long-term outward diffusions ofboth Fe and Cr. In the Ni-rich layer, Cr had been depleted. Simultaneously, the inward diffusion of O and S through the scale alsooccurred, causing internal oxidation and sulfidation along the grain boundaries.

In the severe oxidation stage, nevertheless, the outward diffusions not only occurred in Fe and Cr, but also in Ni. Due to thediffusion of Fe being faster than Cr, a Cr-rich (35%) core formed in the remaining SS.

Fe

Cr

Fe

Ni

Cr-rich Core

O

S

Inner Oxidation & Sulfidation along the Grain Boundaries

Moderate Oxidation Stage

Severe Oxidation Stage

Outer Oxide Scale

Ni-rich Layer

Remained SS

O

S

Fe+2Cr2O4 and (Fe0.6 Cr0.4)2O3.

Ni-rich Layer

Cr

Fig. 13. The schematic diffusion mechanism of the long-term oxidation behaviour.

427W. Liu / Engineering Failure Analysis 70 (2016) 419–427

5. Conclusions

The failure mode of the fluidisation nozzle was oxidation and sufidation. The root cause of the failure was the ash blockagewhich resulted in the scale cracking due to temperature fluctuation on the nozzle wall. The internal oxidation and sulfidation oc-curred along the grain boundaries. The molten metal sulfides in the scale formed the voids which enhanced diffusion.

The long-term oxidation behaviour of SS 304 in this case study was different from the short-term oxidation studies. The oxidescales were mainly composed of Fe+2Cr2O4 and (Fe0.6 Cr0.4)2O3. In the moderate oxidation stage, a Ni-rich (48%) layer up to65 μm formed due to the outward diffusions of both Fe and Cr. In the severe oxidation stage, the outward diffusions not only oc-curred in Fe and Cr, but also in Ni. A Cr-rich (35%) core formed in the remained SS due to the diffusion of Fe was faster than Cr.

Acknowledgements

The author is grateful to Catherine Hobbis at Research Centre for Surface and Material Science, The University of Auckland,who assisted in the ESEM/EDS operation.

Reference

[1] S.-Y. Cheng, K. Sheng-Lih, T. Wen-Ta, Effect of water vapor on annealing scale formation on 316 SS, Corros. Sci. 48 (2006) 634–648.[2] F. Goutier, S. Valette, A. Vardelle, P. Lefort, Oxidation of SS 304 L in carbon dioxide, Corros. Sci. 52 (7) (July 2010) 2403–2412.[3] P. C.I., P. V., F. E., B. M., et al., Breakaway oxidation of austenitic SSs induced by alloyed sulfur, Corros. Sci. 93 (2015) 100–108.[4] L. Dong-sheng, D. Qi-xun, X.-n. Cheng, R.-r. Wang, H. Yan, High-temperature oxidation resistance of austenitic SS Cr18Ni11Cu3Al3MnNb, J. Iron Steel Res. Int. 19 (5)

(May 2012) 74–78.[5] R.L. Higginson, G. Green, Whisker growth morphology of high temperature oxides grown on 304 SS, Corros. Sci. 53 (5) (May 2011) 1690–1693.[6] X. Xu, Z. Xiaofeng, C. Guoliang, L. Zhaoping, Improvement of high-temperature oxidation resistance and strength in alumina-forming austenitic SSs, Mater. Lett.

65 (21–22) (November 2011) 3285–3288.[7] W. Kuang, X. Wu, H. En-Hou, R. Jiancun, Effect of alternately changing the dissolved Ni ion concentration on the oxidation of 304 SS in oxygenated high temper-

ature water, Corros. Sci. 53 (8) (August 2011) 2582–2591.[8] W. Kuang, X. Wu, H. En-Hou, The oxidation behaviour of 304 SS in oxygenated high temperature water, Corros. Sci. 52 (12) (December 2010) 4081–4087.[9] W. Kuang, X. Wu, H. En-Hou, The use of EBSD to study the microstructural development of oxide scales on 316 SS, Mater. High Temp. 22 (2005) 195–200.

[10] N. Otsuka, Y. Nishiyama, T. Kudo, Breakaway oxidation of TP310S SS foil initiated by Cr depletion of the entire specimen in a simulated flue-gas atmosphere, Oxid.Met. 62 (2004) 121–139.

[11] H. Buscail, M. S. El., R. F., P. S., C. R., C. E., I. C., Characterization of the oxides formed at 1000 °C on the AISI 316L SS—role of molybdenum, Mater. Chem. Phys. 111(2008) 491–496.

[12] V. Alenka, M. Miran, D. Aleksander, H. Nina, B.-P. Marianne, High temperature oxidation of SS AISI316L in air plasma, Appl. Surf. Sci. 255 (5) (30 December 2008)1759–1765 (Part 1).

[13] Z. Jianqiang, B. Kate, Y. D. J., Oxidation, carburisation and metal dusting of 304 SS in CO/CO2 and CO/H2/H2O gas mixtures, Corros. Sci. 50 (11) (July 2008)3107–3115.

[14] I. Saeki, T. Saito, R. Furuichi, H. Konno, T. Nakamura, K. Mabuchi, M. Itoh, Growth process of protective oxides formed on type 304 and 430 SSs at 1273 K, Corros.Sci. 40 (1998) 1295–1302.

[15] I. Saeki, H. Konno, R. Furuichi, The initial oxidation of type 430 SS in O2–H2O–N2 atmospheres at 1273 K, Corros. Sci. 38 (1996) 19–31.[16] I. Jérôme, M. Sébastien, C. Frédéric, et al., High temperature behavior of the metal/oxide interface of ferritic SSs, Corros. Sci. 59 (11) (July 2012) 148–156.[17] M.C. Li, H. Zhang, R.F. Huang, S.D. Wang, H.Y. Bi, Effect of SO2 on oxidation of type 409 SS and its implication on condensate corrosion in automotive mufflers,

Corros. Sci. 80 (2014) 96–103.[18] M.P. Phaniraj, K. Dong-Ik, C.Y. Whan, Effect of grain boundary characteristics on the oxidation behavior of ferritic SS, Corros. Sci. 53 (12) (December 2011)

4124–4130.[19] R. Qingxuan, L. Qinghuan, Y. Xu, W. Xu, L. Jun, X. Xueshan, Nitrogen-induced selective high-temperature internal oxidation behavior in duplex SSs 19Cr-10Mn-

0.3Ni-xN, Corros. Sci. 98 (2015) 737–747.[20] J. Qiumin, L. Jun, Y. Xu, X. Xueshan, Z. Wei, J. Laizhu, High-temperature oxidation of duplex SSs S32101 and S32304 in air and simulated industrial reheating at-

mosphere, Corros. Sci. 52 (9) (September 2010) 2846–2854.[21] L. Lian-Fu, J. Zhou-Hua, R. Yves, High-temperature oxidation of duplex SSs in air and mixed gas of air and CH4, Corros. Sci. 47 (1) (January 2005) 57–68.[22] R. Qingxuan, P. Wei, Y. Xu, L. Jun, X. Xueshan, et al., Self-repairing behavior of oxidation diffusion layer and phase transformationmechanism during tensile test of

19Cr duplex SSs with various Mn content, Corros. Sci. 90 (January 2015) 535–543.[23] M.A.E. Jepson, R.L. Higginson, The influence ofmicrostructure on the oxidation of duplex SSs in simulated propane combustion products at 1000 °C, Corros. Sci. 51

(2009) 588–594.[24] M.P. Brady, G. Muralidharan, D.N. Leonard, et al., Long-term oxidation of candidate cast iron and SS exhaust system alloys from 650 to 800 °C in air with water

vapor, Oxid. Met. 82 (5–6) (December 2014) 359–381.[25] Z. Liang, Z. Qinxin, S.P. M., et al., Field studies of steam oxidation behavior of austenitic heat-resistant steel 10Cr18Ni9Cu3NbN, Eng. Fail. Anal. 53 (July 2015)

132–137.[26] W. Liu, The dynamic creep rupture of a secondary superheater tube in a 43 MW coal-fired boiler by the decarburization and multilayer oxide scale buildup on

both sides, Eng. Fail. Anal. V53 (July 2015) 1–14.[27] T. Jonsson, B. Pujilaksono, H. Heidari, et al., Oxidation of Fe–10Cr in O2 and in O2 + H2O environment at 600 °C: a microstructural investigation, Corros. Sci. 75

(2013) 326–336.[28] H. Baker, Alloy Phase Diagrams. ASTM Handbook, V3, ASTM International, 2002 2–316.