High-Temperature Performance of CNT-Based Nanocomposite Coatings on Boiler Tubes: A Critical and Comparative Review of Recent Advances

High-Temperature Performance of CNT-Based Nanocomposite Coatings on Boiler Tubes: A Critical and Comparative Review of Recent Advances

Sandeep Kumar

Department of Mechanical Engineering Guru Kashi University (GKU) Bathinda, Punjab, India sandeep_ycoe@yahoo

Rakesh Bhatia

Yadavindra Department of Engineering, Punjabi University Guru Kashi Campus, Bathinda, Punjab, India rakesh.bhatia_75@yahoo.in

Abstract Coal-fired thermal power plants have boiler tubes which operate in harsh conditions of high temperature including oxidation, molten salt corrosion and particle erosion which hastens the degradation of the material. Nanocomposite coating made of carbon nanotube (CNT) has recently attracted interest as a superior-protective system since it is of excellent mechanical strength, thermal stability and crack-bridging ability. This review is a critical analysis of the recent developments in CNT- based ceramic and metallic coating on boiler-grade steels. Emphasis is placed on plasma sprayed and HVOF deposited systems of the type Al2O3-TiO2-CNT, ZrO2-Y2O3-CNT and NiCr- Cr3C2-CNT coatings. The effects of CNT addition on microstructural refinement, porosity, better interfacial bonding and hardness are discussed in respect of oxidation and erosion- corrosion resistance up to 900 deg C. Comparative results show that optimized CNT content is much better in terms of integrity of the coating and high temperature durability. Nevertheless, nanotube agglomeration, thermal degradation, and dispersion control are some of the main concerns that should be solved. The review synthesizes structure-property-performance association and outlines the future research to come up with dependable CNT-based protective coating in the high-temperature boiler applications.

Keywords-Carbon-nanotubes (CNTs), Nano-composite coatings, Boiler tubes, High temperature oxidation, Erosion corrosion resistance

1. INTRODUCTION

   Thermal power plants have boiler tubes which are subjected to hostile conditions of high temperature (600-900 deg C), and through the combination of oxidation, hot corrosion, erosion, and thermal fatigue, facilitate materials degradation and early component failure. Long term exposure to molten salts (Na2SO4, V2O5), particles of fly ash, and cyclic changes in temperature hastens the process of oxide scales and spallation thus ultimately leading to a thinning of the wall and to a decrease in service life [1],[2]. Traditional coating or protection like NiCr, NiCrAlY, Al2O3- TiO2 and ZrO2-Y2O3 have been extensively used but the performance is generally restricted by porosity, micro crack formation and poor scale adherency under the impact of cyclic conditions [3], [4].

   Nanostructured materials have recently made new progress in

   the form of carbon nanotube (CNT)-reinforced nanocomposites coating, which is promising as a high-temperature protection. CNTs are very strong in terms of their tensile strength, aspect ratio, and thermal conductivity and all of them increase their ability to bridge cracks and densify the matrix upon uniform dispersion [5],[6]. Experiments have been able to show enhanced corrosion resistance and mechanical integrity properties of CNT-based composite coatings over established systems [7], [8].

   In the past five years, there has been a tremendous research on the introduction of multi-walled CNTs (MWCNTs) into ceramic and metallic matrices deposited through thermal spray and other associated methods to improve the high-temperature behavior [5],[9],[10]. The developments are critically reviewed by focusing on the degradation mechanisms, coating microstructure, oxidation resistance, erosion behavior, as well as future research direction.

2. HIGH-TEMPERATURE DEGRADATION MECHANISMS IN BOILER TUBES

   Minor degradation of boiler tubes is mainly experienced as a result of high-temperature oxidation, hot corrosion, erosion- corrosion, and thermal fatigue.

   Oxidation at high temperatures causes Fe2O3, Fe3O4 and Cr2O3 scale which continues to increase and ultimately spalls during repeated stresses [11], [12], [13]. Molten salt deposits enhance the rates of hot corrosion in coal-fired boilers, which boosts the rates of metal losses. There has been increased resistance to oxidation on the layers of the thermal spray; evidently, the porosity at microstructural levels and splat limits serve as diffusion routes of corrosive elements [13], [14], [15].

   Fig.1 Damage and perforation of the boiler tubes were caused by erosion- corrosion (TSPCL)

   The Figs.(a)-(d) demonstrates the progressive erosion corrosion damages in boiler tubes that undergo service conditions of high temperatures. Localized wall thinning and pitting is also experienced because of particle impingement and corrosive attack.Splintering of oxide scales also enhances the rate of material wear.

   Both extreme degradation causes through-wall perforation of the tubes.

   The erosion-corrosion takes place because of high-velocity fly ash/particulate impact, which removes the protective oxides scales and the underlying substrate is exposed. The CNT reinforced NiCr-Cr3C2 coating has been shown to have lower erosion rates because they are better densified and offer better crack resistance [16], [17].

   Repeated heating and cooling cycles cause thermal fatigue which causes stress due to thermal mismatch between coating and substrate. NT addition increases crack-bridging and prevents crack propagation, which increases coating longevity [18], [19].

3. CNT-BASED NANOCOMPOSITE COATING SYSTEMS AND DEPOSITION TECHNIQUES

   1. Ceramic Matrix Systems

      Hot corrosion resistance and mass gain at high temperatures have been reported to be improved by the incorporation of CNT into Al2O3-TiO2, ZrO2-Y2O3 matrices [20] [21], [22]. The higher hardness and toughness of fractures are credited to CNTs introducing crack deflection and crack bridging [23]. Optimized CNT content (0.5-2 wt%) decreases porosity and it enhances oxide scale adhesion [24].

      Fig. 2. Flow chart of CNT-based nanocomposites coating and deposition methods

      The fig. 2 shows an overview of CNT-based nanocomposite

      coating systems and their classification. It highlights commonly used ceramic and cermet matrices reinforced with CNTs. Major thermal spray deposition techniques such as plasma spraying, HVOF, and HVAF are also illustrated.

   2. Metallic and Cermet Systems

      CNTs reinforced with metallic matrices like NiCrAlY show better resistance to oxidation and better density of the coating when deposited using HVOF methods [25]. In a similar manner, CNT-modified NiCr-Cr3C2 Coatings exhibit greater erosion resistance and reduced weight loss when compared to non-reinforced Coatings [2], [26]. The study on NiCo-CNT composite coatings also demonstrates the enhanced corrosion resistance because the grain is refined, and the density of the defects is low [26], [27].

   3. Deposition Techniques

   CNT-based coating is done by Atmospheric Plasma Spray (APS) and High Velocity Oxy-Fuel (HVOF) [28] [29]. However, the dispersion of CNTs is still a problem because of agglomeration forces [30]. CNT dispersion and matrix bonding are enhanced through surface functionalization and optimized feedstock preparation [31].

4. Comparative High-Temperature Performance

   1. Hardness and Mechanical Properties

      CNT reinforcement has a large enhancement on hardness and fracture toughness. It is suspected by studies of romoting hardening of up to 15-30 percent in coating with CNT compared to conventional systems [32], [33]. The propagation rates are decreased by crack-bridging mechanisms in case of thermal stress [34].

      Table 1. Comparative properties and microstructural characterization of CNT- reinforced coating

      Coating System	Key Findings (H = Hardness, P = Porosity)
      ZrOYO (0%)	H: 789796 HV; P: 4.25%; dense splats; ZrYO phases [21]
      ZrOYO (1% wt% CNT)	H: ~910 HV; P: 3.62%; uniform CNT; +C peak; Zr YOC [21]
      ZrOYO (4% wt% CNT)	H: ~1050 HV; P: 3.45%; dense lamellae; stable phases +C [21]
      CrO (26% wt% CNT, HVOF)	H (max 6%); P ; uniform CNT; CrO retained [12]
      CrC25NiCr (0 7% wt% CNT, HVOF)	H (max 7%); P: 1.176% (min); dense; CrNiC [13]
      AlO13TiO +1.5% wt% CNT	H ; P ; homogeneous; stable phases [45]
      YSZAlO +3% wt% CNT	H ; roughness ; tough morphology; YSZ confirmed [46]
      WCCo +1% wt% CNT	~30% H ; P ; better cohesion; WC retained [47]
      WCCoCr +0.3% wt% CNT	1420 vs 1357 HV; 1.81% vs 2.73%; dense; WC, CoWC [48]

      As presented in Table 1 the comparative outcomes do reveal that the CNT reinforcement is greatly contributing to coating performance especially hardness and densification. Hardness in zirconia-based based on CNT addition showed a strong rise ( 790 HV to 1050 HV), and porosity was always reduced, showing a better compactness of the coating. The same is seen in Cr3C2-NiCr and WC-based coatings, in which incorporation

      of CNT enhanced microhardness and lowered the amount of defects. Analysis of SEM across studies reveals more homogenous and dense microstructures having superior inter- splat bonding. The analysis of XRD shows that CNTs are chemically stable and do not develop unwanted phases, whereas the EDAX/EDS method proves that carbon is incorporated successfully. All in all, CNTs are useful reinforcement agents, enhancing mechanical strength, structural integrity, and coating quality of high temperature protection systems.

   2. Oxidation and Hot Corrosion Resistance

      Hot corrosion tests has been conducted at 900 deg C and show the reduced mass gain in CNT reinforced ceramic coatings due to the denser oxide formation and the improved scale adherence [21], [35]. The performance of NiCrAlY-CNT systems is better than that of oxidation kinetics as compared to the base coating [36].

   3. Erosion-Corrosion Performance

      According to erosion researches, CNT-reinforced NiCr-Cr3C2 coating experiences less mass loss at high impact angles since the toughness of the matrices is increased [4]. Enhanced lamellar cohesion minimizes the crack generation and material abrasion [37].

   4. Thermal Stability

   Even though CNTs improve the performance at moderate high temperatures, the oxidation of CNTs beyond the temperature of about 800 deg C can be detrimental to the reinforcement effect of CNTs [38]. Content of CNT (>2 wt%) enhances agglomeration and poor interfacial bonding [39].

5. Limitations and Research Gaps

   Despite some promising laboratory results were achieved, there are still a number of challenges:

   • Oxidation CNT during very high temperatures [40]

   • The problem of agglomeration and dispersion [41]

   • Minimal cyclic oxidation data in the long run [42]

   • Scaling up and industrial validation issues [43]

   • Combined methods of CNTs with graphene or ceramic nanoparticles can be used as a method of enhancement of thermal stability [44].

6. Conclusions

The nanocomposites developed on the basis of CNTs provide greater advances in hardness, oxidation resistance and erosion- corrosion characteristics as compared to the traditional coating applied on the boiler tubes. Ceramic-CNT systems are characterized by a better oxidation resistance and metallic CNT composites are characterized by better erosion performance. The ideal CNT content (0.5-2 wt) is essential to ensure that the maximum benefits are achieved without the agglomeration. Future work on boosting emission monitored in this area should focus on long-term cyclic oxidation studies, development of advanced dispersion techniques and industrial scale formulations to help with widespread usage in high temperature boilers.

ACKNOWLEDGMEN

The authors establishes that no external funds were used in this research. The infrastructural and academic assistance which is

being given by the affiliated institution is highly valued.

REFERENCES

1. G. Madhu, K. M. Mrityunjaya Swamy, D. A. Kumar, C. D. Prasad, and U. Harish, Evaluation of hot corrosion behavior of HVOF thermally sprayed Cr3C2-35NiCr coating on SS 304 boiler tube steel, American Institute Of Physics, Jan. 2021. doi: 10.1063/5.0038279.

2. K. Derelizade, A. Rincon, F. Venturi, R. G. Wellman, A. Kholobystov, and T. Hussain, High temperature (900 °C) sliding wear of CrNiAlCY coatings deposited by high velocity oxy fuel thermal spray, Surface and Coatings Technology, vol. 432, p. 128063, Feb. 2022, doi: 10.1016/j.surfcoat.2021.128063.

3. M. Oksa, S. Tuurna, and T. Varis, Increased Lifetime for Biomass and Waste to Energy Power Plant Boilers with HVOF Coatings: High Temperature Corrosion Testing Under Chlorine-Containing Molten Salt, J Therm Spray Tech, vol. 22, no. 5, pp. 783796, Apr. 2013, doi: 10.1007/s11666-013-9928-5.

4. G. Prashar, H. Vasudev, and L. Thakur, HIGH-TEMPERATURE OXIDATION AND EROSION RESISTANCE OF NI-BASED THERMALLY-SPRAYED COATINGS USED IN POWER GENERATION MACHINERY: A REVIEW, Surf. Rev. Lett., vol. 29, no. 03, Dec. 2021, doi: 10.1142/s0218625x22300039.

5. Y. Fu, J. Zhao, X. Li, and Y. Peng, Corrosion resistance of MWCNTs- nanoZnO composite reinforced chromium-free Zn-Al coating, ACMM, vol. 71, no. 6, pp. 640649, Sept. 2024, doi: 10.1108/acmm-01-2024-

   2948.

6. H. Wang et al., Synergistic Dispersion and Interfacial Reinforcement of

   <scp>MWCNTs</scp> in <scp>PA6</scp> Nanocomposites Enabled by

   <scp>PVP</scp>: Enhancing Mechanical Performance, Polymer Engineering &amp; Sci, Oct. 2025, doi: 10.1002/pen.70194.

7. V. V. Popov, A. Pismenny, N. Larianovsky, A. Lapteva, and D. Safranchik, Corrosion Resistance of AlCNT Metal Matrix Composites, Materials, vol. 14, no. 13, p. 3530, June 2021, doi: 10.3390/ma14133530.

8. N. A. Ali, S. I. Hussein, T. B. Asafa, and A. M. Abd-Elnaiem, Mechanical Properties and Electrical Conductivity of Poly(methyl methacrylate)/Multi-walled Carbon Nanotubes Composites, Iran J Sci Technol Trans Sci, vol. 44, no. 5, pp. 15671576, Aug. 2020, doi: 10.1007/s40995-020-00948-7.

9. R. Chaturvedi, A. Sharma, K. Sharma, and M. Saraswat, Tribological behaviour of multi-walled carbon nanotubes reinforced AA 7075 nano- composites, Advances in Materials and Processing Technologies, vol. 8, no. 4, pp. 47434755, May 2022, doi: 10.1080/2374068x.2022.2080330.

10. X. Ye et al., Carbon Nanotubes (CNTs) Reinforced CoCrMoNbTi0.4 Refractory High Entropy lloy Fabricated via Laser Additive Manufacturing: Processing Optimization, Microstructure Transformation and Mechanical Properties, Crystals, vol. 12, no. 11, p. 1678, Nov. 2022, doi: 10.3390/cryst12111678.

11. K. Kumar, S. Kumar, and H. Singh Gill, HIGH-TEMPERATURE OXIDATION PERFORMANCE OF HVOF AND PLASMA-SPRAYED Ni-20Cr, Ni-20Cr + TiC, AND Ni-20Cr + TiN COATINGS ON T22

    BOILER STEELS, Surf. Rev. Lett., Apr. 2025, doi: 10.1142/s0218625x25501306.

12. K. Goyal, H. Singh, and R. Bhatia, Behaviour of carbon nanotubes- Cr2O3 thermal barrier coatings in actual boiler, Surface Engineering, vol. 36, no. 2, pp. 124134, Mar. 2019, doi: 10.1080/02670844.2019.1584966.

13. S. Singh, K. Goyal, and R. Bhatia, Molten sulphate vanadateinduced hot corrosion behaviour of YSZ-reinforced thermal spray coatings at elevated temperature, ACMM, vol. 72, no. 1, pp. 93106, Nov. 2024, doi: 10.1108/acmm-08-2024-3071.

14. S. Kumar, A. Handa, V. Chawla, N. K. Grover, and R. Kumar, Performance of thermal-sprayed coatings to combat hot corrosion of coal-fired boiler tube and effect of process parameters and post-coating heat treatment on coating performance: a review, Surface Engineering, vol. 37, no. 7, pp. 833860, May 2021, doi: 10.1080/02670844.2021.1924506.

15. D. Dhand, P. Kumar, and J. S. Grewal, A review of thermal spray coatings for protection of steels from degradation in coal fired power plants, Corrosion Reviews, vol. 39, no. 3, pp. 243268, Apr. 2021, doi: 10.1515/corrrev-2020-0043.

16. P. Selvam Kevin, A. Tiwari, S. Seman, S. A. Beer Mohamed, and R. Jayaganthan, Erosion-Corrosion Protection Due to Cr3C2-NiCr Cermet Coating on Stainless Steel, Coatings, vol. 10, no. 11, p. 1042, Oct. 2020, doi: 10.3390/coatings10111042.

17. J. Mehta, V. Mittal, and P. Gupta, Role of Thermal Spray Coatings on Wear, Erosion and Corrosion Behavior: A Review, vol. 20, no. 4, pp.

    445452, Dec. 2017, doi: 10.6180/jase.2017.20.4.05.

18. K. F. Chan, M. H. M. Zaid, M. S. Mamat, S. Liza, M. Tanemura, and Y. Yaakob, Recent Developments in Carbon Nanotubes-Reinforced Ceramic Matrix Composites: A Review on Dispersion and Densification Techniques, Crystals, vol. 11, no. 5, p. 457, Apr. 2021, doi: 10.3390/cryst11050457.

19. Z. Niu et al., Mechanical and thermal shock properties of C f /SiBCN composite: Effect of sintering densification and fiber coating, J Am Ceram Soc., vol. 105, no. 6, pp. 43214335, Feb. 2022, doi: 10.1111/jace.18364.

20. R. Goyal and K. Goyal, Development of CNT reinforced Al2O3-TiO2 coatings for boiler tubes to improve hot corrosion resistance, J. Electrochem. Sci. Eng., Aug. 2022, doi: 10.5599/jese.1291.

21. S. Kumar, R. Bhatia, and H. Singh, Hot corrosion behaviour of CNT- reinforced ZrO2-Y2O3 composite coatings on boiler tube steel at 900°C, ACMM, vol. 68, no. 6, pp. 503515, Oct. 2021, doi: 10.1108/acmm-12-

    2020-2412.

22. S. Kumar, R. Bhatia, H. Singh, and R. L. Virdi, Microstructural and mechanical properties of CNT-reinforced ZrO2-Y2O3 coated boiler tube steel T-91, J. Electrochem. Sci. Eng., July 2022, doi: 10.5599/jese.1228.

23. A. Y. Al-Maharma, P. Sendur, and N. Al-Huniti, Critical review of the factors dominating the fracture toughness of CNT reinforced polymer composites, Mater. Res. Express, vol. 6, no. 1, p. 012003, Oct. 2018, doi: 10.1088/2053-1591/aae867.

24. G. Wang, X. Liu, M. Wang, M. Yu, H. Zhang, and L. He, Enhancing interlaminar fracture toughness of carbon fiber/epoxy composites toughened by polyethersulfone resin and hybrid carbon nanotubes/graphene oxide, Polymer Composites, vol. 46, no. 5, pp. 45194533, Nov. 2024, doi: 10.1002/pc.29256.

25. B. Seitov et al., Review of Physical and Mechanical Properties, Morphology, and Phase Structure in Cr3C2-NiCr Composite Coatings Sprayed by HVOF Method, Coatings, vol. 15, no. 4, p. 479, Apr. 2025, doi: 10.3390/coatings15040479.

26. K. Goyal and R. Goyal, Improving hot corrosion resistance of Cr3C2 20NiCr coatings with CNT reinforcements, Surface Engineering, vol. 36, no. 11, pp. 12001209, Sept. 2019, doi: 10.1080/02670844.2019.1662645.

27. S. Brioua et al., Influence of Spray Parameters on the Metallurgical and Functional Properties of HVOF WC Based Cermets Deposited onto Low Alloy Steel, J. Mater. Sci. Technol. Res., vol. 9, no. 1, pp. 110, Oct. 2025, doi: 10.31875/2410-4701.2022.09.01.

28. E. Bakan, D. Marcano, D. Zhou, Y. J. Sohn, G. Mauer, and R. Vaßen, Yb2Si2O7 Environmental Barrier Coatings Deposited by Various Thermal Spray Techniques: A Preliminary Comparative Study, J Therm Spray Tech, vol. 26, no. 6, pp. 10111024, June 2017, doi: 10.1007/s11666-017-0574-1.

29. I. A. Alnaser, M. Yunus, R. Alfattani, and T. Alamro, High-Temperature Corrosion of APS- and HVOF-Coated Nickel-Based Super Alloy under Air Oxidation and Melted Salt Domains, Materials, vol. 14, no. 18, p. 5119, Sept. 2021, doi: 10.3390/ma14185119.

30. K. Balani, S. R. Bakshi, Y. Chen, T. Laha, and A. Agarwal, Role of Powder Treatment and Carbon Nanotube Dispersion in the Fracture Toughening of Plasma-Sprayed Aluminum OxideCarbon Nanotube Nanocomposite, J. Nanosci. Nanotech., vol. 7, no. 10, pp. 35533562, Oct. 2007, doi: 10.1166/jnn.2007.851.

31. Z.-G. Ban and L. L. Shaw, Characterization of Thermal Sprayed Nanostructured WC-Co Coatings Derived From Nanocrystalline WC- 18wt.%Co Powders, Journal of Thermal Spray Technology, vol. 12, no. 1, pp. 112119, Mar. 2003, doi: 10.1361/105996303770348564.

32. N. Domun, H. Hadavinia, T. Zhang, T. Sainsbury, G. H. Liaghat, and S. Vahid, Improving the fracture toughness and the strength of epoxy using nanomaterials–a review of the current status., Nanoscale, vol. 7, no. 23,

    pp. 1029410329, Jan. 2015, doi: 10.1039/c5nr01354b.

33. M. Nurguzhin et al., Structure and Properties of AlCNT-Based Composites Manufactured by Different Methods: A Brief Review, Materials, vol. 18, no. 1, p. 214, Jan. 2025, doi: 10.3390/ma18010214.

34. J. Shi, X. Zong, W. Jiang, R. Yao, and J. Zheng, Evaluation of the Fracture Toughness of Short Carbon Fiber Reinforced Thermoplastic Composites, American Society Of Mechanical Engineers, July 2023. doi: 10.1115/pvp2023-107021.

35. K. Goyal, H. Singh, and R. Bhatia, Cyclic high temperature corrosion studies of carbon nanotubes-Cr2O3 composite coatings on boiler steel at 900°C in molten salt environment, ACMM, vol. 65, no. 6, pp. 646657, Sept. 2018, doi: 10.1108/acmm-06-2018-1954.

36. M. S. Reddy G, C. D. Prasad, P. Patil, N. Kakur, and M. R. Ramesh,

    Elevated temperature erosion performance of plasma sprayed NiCrAlY/TiO2 coating on MDN 420 steel substrate, Surf. Topogr.: Metrol. Prop., vol. 10, no. 2, p. 025010, May 2022, doi: 10.1088/2051- 672x/ac6a6e.

37. G. Niu et al., Superior fracture toughness in a high-strength austenitic steel with heterogeneous lamellar microstructure, Acta Materialia, vol. 226, p. 117642, Jan. 2022, doi: 10.1016/j.actamat.2022.117642.

38. W. L. Baloch, R. A. Khushnood, and W. Khaliq, Influence of multi- walled carbon nanotubes on the residual performance of concrete exposed to high temperatures, Construction and Building Materials, vol. 185, pp. 4456, July 2018, doi: 10.1016/j.cobuildmat.2018.07.051.

39. H. Peng et al., Enhancing the Interfacial Interactions and Thermal Oxidative Mechanical Properties of Aramid FiberReinforced Epoxy Composites Through Hyperbranched EpoxyGrafted MultiWalled Carbon Nanotubes, Polymer Composites, July 2025, doi: 10.1002/pc.70244.

40. C. Pan et al., Corrosion Control by Carbon-Based Nanomaterials: A Review, ACS Appl. Nano Mater., vol. 7, no. 3, pp. 25152528, Jan. 2024, doi: 10.1021/acsanm.3c05547.

41. Y. Zhang, Q. Wang, G. Chen, and C. S. Ramachandran, Mechanical, tribological and corrosion physiognomies of CNT-Al metal matrix composite (MMC) coatings deposited by cold gas dynamic spray (CGDS) process, Surface and Coatings Technology, vol. 403, p. 126380, Sept. 2020, doi: 10.1016/j.surfcoat.2020.126380.

42. S. S. Kumar, C. D. Prasad, and H. Hanumanthappa, Role of Thermal Spray Coatings on Erosion, Corrosion, and Oxidation in Various Applications: A Review, J Bio Tribo Corros, vol. 10, no. 2, Feb. 2024, doi: 10.1007/s40735-024-00822-8.

43. U. P. Gaur and E. Kamari, Applications of Thermal Spray Coatings: A Review, JTSE, vol. 4, pp. 106114, Jan. 2024, doi: 10.52687/2582- 1474/405.

44. B. Monteiro and S. Simões, Recent Advances in Hybrid Nanocomposites for Aerospace Applications, Metals, vol. 14, no. 11, p. 1283, Nov. 2024, doi: 10.3390/

45. Lan, Wei, et al. "Corrosion resistance analysis of Al2O3-TiO2 composite ceramic coatings on carbon steel pipe surfaces." Alexandria Engineering Journal 110 (2025): 377-385.

46. Thakare, J. G., et al. "Mechanical property evaluation of carbon nanotubes reinforced plasma sprayed YSZ-alumina composite coating." Ceramics International 44.6 (2018): 6980-6989.

47. Mohanty, Deviprasanna, et al. "Carbon nanotube reinforced HVOF sprayed WC-Co coating." Materials & Design 156 (2018): 340-350.

48. Zhang, Zihan, et al. "Microstructure and mechanical properties of HVOF- sprayed WC-based cermet composite coating reinforced by MWCNT@ MXene." Surface and Coatings Technology (2025): 133071.