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Article

Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C

by
Junjie Wu
1,†,
Changlin Yang
2,†,
Fan Zhao
2,*,
Yi Zeng
2,
Jianping Lai
2,
Jiaxin Yu
2,*,
Yingbo Guan
1,
Zhenhuan Gao
1 and
Xiufang Gong
1
1
State Key Laboratory of Clean and Efficient Turbomachinery Power Equipment, Dongfang Electric Corporation Dongfang Turbine Co., Ltd., Deyang 618000, China
2
Key Laboratory of Testing Technology for Manufacturing Process in Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Coatings 2026, 16(1), 128; https://doi.org/10.3390/coatings16010128
Submission received: 18 December 2025 / Revised: 7 January 2026 / Accepted: 9 January 2026 / Published: 19 January 2026
(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)
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Abstract

Welding repair of cracks in FSX-414 cobalt-based alloy, used in high-temperature components, poses significant challenges due to the presence of surface oxide films within the cracks. By comparing the formation of oxide films on the external surface and inside the narrow crevice of FSX-414 alloys preserved at 900 °C for up to 1000 h, we found that the oxide film growth rate on the external surface was slightly larger than that inside the narrow crevice, and the latter slowed down after 672 h. Additionally, the oxide films on both surfaces were mainly composed of O and Cr elements, providing excellent protection to the underlying metal and resulting in minimal internal oxidation. A compositional transition region formed between the oxide film and the base metal. The width of the transition region decreased with heating duration and was narrower in the external surface sample, leading to a steeper composition gradient between the oxide film and the inner metal. With prolonged exposure, increasing numbers of “pores” rich in W and O appeared near the oxide films, creating channels that connect the oxide layer with the internal metal and accelerate material degradation. “Pores” extended deeper into the metal within the narrow crevice compared to those on the surface. Prior to welding repair, channels composed of W and O near the oxide films must be cleaned along with the oxide layer itself, and the removal of oxide from narrow cracks poses greater difficulty.

1. Introduction

Aero-engines and gas turbines, which serve as core power equipment characterized by high technical density and complex manufacturing processes, are widely used in the fields of energy, aerospace, and power generation [1,2,3]. High-temperature components of these systems, such as turbine blades [4], guide vanes [5], and combustion chambers [6], endure long-term exposure to high temperatures, high pressures, and complex mechanical loads [7,8], making them susceptible to crack formation [9,10,11]. For example, the primary turbine blades and guide vanes of a power station gas turbine fractured after approximately 18,420 h of operation at about 800 °C [12], owing to microstructural deterioration caused by overheating. Similarly, second-stage nozzles of a 100 MW gas turbine, manufactured from FSX-414 cobalt-based alloy [13], developed crack networks and failed after 32,000 h of high-temperature service as a result of carbide transformation into continuous brittle grain boundaries.
FSX-414 cobalt-based superalloy is widely used in high-temperature components due to its excellent creep strength, hot corrosion resistance, and wear resistance [14]. However, surface cracks in such components pose a serious hazard to service safety and often require repair, given the high cost and complexity of manufacturing [15]. Welding is commonly employed as an effective repair technique [16]. Shallow cracks near the surface can be easily restored by mechanically removing the defective coating, followed by re-preparing and re-coating [17]. In contrast, deep cracks are difficult to remove completely for practical and economic reasons and are more suitably repaired by brazing [18]. The quality and strength of brazed joints depend essentially on the surface treatment of the cracks, particularly the removal of the oxide film [19]. Chemical methods are often used for oxide removal [20], where understanding the growth process and formation mechanism of the oxide film is imperative to design a tailored cleaning procedure—including cleaning time and solution composition [21,22].
The formation of a continuous and stable oxide film is crucial for protecting superalloys during high-temperature service [23,24,25], yet it also presents a major challenge during cleaning [26,27,28]. The oxide film on metal surfaces acts as a “protective barrier”, effectively inhibiting further penetration of external media into the substrate [29,30,31], a feature that has attracted considerable attention. The oxide kinetics of cobalt-based alloys vary with temperature [32], and alloying elements play distinct roles [33]. For instance, Cr preferentially undergoes selective oxidation at elevated temperatures to form a dense Cr2O3 oxide layer. This layer effectively inhibits the inward diffusion of oxygen and outward migration of matrix elements, thereby significantly enhancing the oxidation resistance of the alloy [34]. The observed decrease in mass gain after oxidation at 900 °C for 100 h [35] is primarily due to Ni, which leads to the formation of solid solutions with Cr2O3 and thereby enhances the oxide film’s structural stability. W tends to segregate at the oxide-film/substrate interface or precipitate as fine WOx particles due to its low diffusion coefficient in the matrix [36].
However, existing studies on the oxidation of FSX-414 alloy have primarily focused on external surfaces under oxygen-rich conditions [37,38,39], while neglecting the oxidation behavior within narrow crevices. Unlike the external surface, the space-confined geometry of narrow crevices leads to both a lower oxygen partial pressure and restricted gas transport [40,41]. These conditions inevitably affect both the formation of the oxide layer and the design of its removal process. Without understanding these differences, it is difficult to formulate targeted cleaning strategies for deep cracks—a key research gap that remains to be addressed.
In this paper, FSX-414 alloy samples with designed narrow crevices were subjected to oxidation at 900 °C for durations up to 1000 h. After the oxidation process, the oxide films, which formed on the external surface and within the narrow crevice, were compared in terms of cross-sectional morphology and element distribution. The growth process and formation mechanism of the oxide films were discussed, providing a reliable theoretical basis for customized cleaning procedures and laying a solid foundation for the welding repair of deep cracks in high-temperature components.

2. Materials and Methods

The cast FSX-414 alloy (Co-30Cr-10Ni-7W) (wt.%) was sliced into rectangular blocks (30 mm × 10 mm × 5 mm) and polished with a surface roughness of about 8~10 μm. Two pieces of the alloy were welded to generate the narrow crevice in order to overcome the limitations associated with conventional mechanical techniques—including plastic deformation, work hardening, and surface contamination introduced by processes such as wire electrical discharge machining or milling. The schematic diagram of the welding process is shown in Figure 1a. The 10 mm × 5 mm surfaces of two samples were polished to a roughness of 0.8 μm and brought into contact to form a crevice. The use of a continuous Ni ribbon was found to produce a V-shaped crevice profile, which led to a non-uniform width along its depth. To address this issue, nickel foil was placed at both ends of the specimen to achieve a consistent crevice geometry. Finally, laser welding was employed to weld both ends and the top edge of the crevice. The welding power was set at 200 W, and the welding speed was about 100 mm/s. The upper and bottom surfaces of the welded assembly are shown in Figure 1b and Figure 1c, respectively. By this method, the crevice thickness was maintained at a constant value and measured at least three times to ensure the precision.
The welded specimens were maintained at 900 °C in static air for durations of 168 h, 336 h, 504 h, 672 h, and 1000 h, respectively, using a muffle furnace (DTN-8A-16, Dengsheng Instrument Manufacturing Co., Ltd., Shanghai, China). A heating rate of 75 °C/min was applied, followed by furnace cooling. After oxidation, samples with dimensions of 10 mm × 8 mm × 6 mm were cut from the oxidized specimens, as illustrated in Figure 2. The cross-sectional surfaces were ground and polished to expose the oxide films formed within the narrow crevice and on the external surface for analysis. The cross-sectional morphology of these oxide films was investigated by scanning electron microscope (SEM, ZEISS Sigma 360, Oberkochen, Germany). Element distribution was analyzed using energy dispersive X-ray spectroscopy (EDS, ZEISS Sigma 360, Oberkochen, Germany) equipped on the SEM.

3. Results and Discussion

3.1. Oxide Film in the Narrow Crevice of FSX-414 Alloy

Figure 3 presents the morphology and composition of the unoxidized crevice in FSX-414 cobalt-based alloy. The width of the narrow crevice was measured to be approximately 58.11 μm, as shown in Figure 3a. Figure 3b and Figure 3c display the cross-sectional morphology and the corresponding element distribution of the alloy, respectively. Elements including Co, Cr, Ni, O, W, Mn, and Fe were uniformly distributed in the matrix. As indicated in Figure 3d, Co and Cr constituted the majority, with contents of 49.77 at. % and 31.78 at. %, respectively. Ni, O, and W were present in lower amounts (10.35 at. %, 4.80 at. %, and 2.56 at. %, respectively), while Mn and Fe were detected only in trace quantities.
Figure 4 shows the cross-sectional morphologies and oxide film thickness of the crevice held at 900 °C for various durations. The oxide films exhibited a dense structure and adhered closely to the underlying metal. In the designed crevice structure (approximately 58 μm in width and no more than 10 mm in depth), the oxide film thickness showed negligible variation. However, discrete “pores” were observed within the metal adjacent to the oxide interface. Both the size and number of these “pores” increased with prolonged heating time. As the duration extended from 168 h to 1000 h, the maximum size and area fraction in the inner metal of the “pores” increased from 0.40 μm and 1.3% to 1.47 μm and 12.5%, respectively. Similarly, the oxide film thickness of the crevice elevated from 2.67 to 6.14 μm. Notably, the growth rate of the oxide film within the narrow crevice was higher during the initial 672 h (approximately 8.97 × 10−3 μm/h) compared to that between 672 h and 1000 h (approximately 0.34 × 10−3 μm/h). This slower growth beyond 672 h was attributed to the protective nature of the oxide layer and the lower oxygen partial pressure inside the space-confined crevice [40,41].
The element distributions along linear scans from the oxide film to the inner metal on the cross-sections of the crevice region after different heating durations are shown in Figure 5a–e, the red arrows in the image indicate the direction of line scanning. The oxide film was mainly composed of Cr and O elements, corresponding to chromium oxides. A sharp gradient in Cr and O contents was observed from the oxide layer toward the inner metal, with a distinct transition region between the two. The transition regions, characterized as blue areas in the line scan images, represent the compositional transition zone between the oxide film and the inner metal. These zones were defined based on quantitative EDS analysis: the starting point corresponds to a significant decrease in oxygen content, and the endpoint is marked by stabilization of the cobalt content. The width of the transition region decreased from 1.57 to 1.05 μm as the heating duration increased from 168 h to 1000 h. A larger compositional variation gradient between the oxide film and the inner metal caused by the smaller transitional region width could lead to poor adhesion between the oxide coating and the internal metal [42]. As a result, mechanical vibration combined with chemical treatment should be a good cleaning method for removing oxide film formed during long-term service [20].
Further, element distribution across the cross-section of the narrow crevice specimen preserved for 168 h is shown in Figure 6. It was clear that Cr and O were mainly distributed on the oxide film, which was in accordance with the results of Figure 5. While “pores” in the inner metal were mainly composed of W and O, referring to tungsten oxide. Not only the oxide film but also the layer adjacent to the oxide film in the inner metal should be considered during the treatment before the welding repair.
Element distribution across the cross-section of the narrow crevice specimen preserved for 1000 h showed similar results, as shown in Figure 7. A comparison of Figure 6 and Figure 7 revealed that with increasing heating duration, W and O contents within the “pores” exhibited a more pronounced discrepancy relative to the surrounding metal, while the distribution became more continuous and deeper in the inner metal. This increased discrepancy was attributed to the continuous element diffusion and, thus, contributed to severe segregation, which accelerated the deterioration [35].

3.2. Oxide Film in the External Surface of FSX-414 Alloy

Figure 8 shows the cross-sectional morphologies and oxide film thickness of the external surface held at 900 °C for various durations. Accordingly, the oxide films showed a compact structure bonded closely to the inner metal, and “pores” were discretely distributed in the inner metal near the oxide film, which was in accordance with the results of the narrow crevice. With the heating duration increasing from 168 h to 1000 h, the maximum size and area fraction in the inner metal of the “pores” increased from 0.91 μm and 5.6% to 1.58 μm and 24.5%, while the thickness of the oxide film increased from 2.51 μm to 7.03 μm. The growth rate of the oxide film on the external surface behaved consistently with the value of about 7.03 × 10−3 μm/h within 1000 h, which was different from the narrow crevice. The adequate oxygen supplied to the external surface resulted in a continuous growth of oxide film, which showed a larger thickness. By contrast, oxidation within the narrow crevice was slowed due to the low oxygen partial pressure. In addition, “pores” of the external surface specimens showed a larger size and quantity compared with the corresponding narrow crevice specimens.
The element distributions along linear scans from the oxide film to the inner metal on the cross-sections of the external surface after different heating durations are shown in Figure 9a–e, the red arrows in the image indicate the direction of line scanning. respectively. Accordingly, the contents of Cr and O elements showed dramatic changes from the oxide film to the inner metal, leaving a transition region between these two parts, and the width of the transition region decreased with the heating duration. However, the width of the transition region in the external surface was smaller (changing from 1.31 to 0.81 μm) compared with the corresponding value (from 1.57 to 1.05 μm) in the narrow crevice, which contributed to the sufficient oxygen and the rapid element diffusion [34]. In the external surface, rapid element exchange results in a sharp compositional gradient at the interface, forming a narrower transition region. The pronounced gradient intensifies the mismatch in physical properties, raises the interfacial shear stress, and weakens the adhesion between the oxide film and the inner metal [42]. As a result, the oxide film on the external surface was easier to remove than that within the narrow crevice.
Further, element distribution across the cross-section of the external surface specimen preserved for 168 h is shown in Figure 10. It was clear that Cr and O were mainly distributed on the oxide film, while “pores” in the inner metal were mainly composed of W and O (meaning tungsten oxide), which was in accordance with the results of Figure 9.
Figure 11 shows the element distribution across the cross-section of the external surface specimen preserved for 1000 h. Like the crevice specimen, the contents of W and O in the “pores” showed more significant discrepancy compared with the surrounding metal as the heating duration increased. Notable differences were also observed: the underlying metal on the external surface exhibited more shallowly distributed pores compared to those within the narrow crevice. This can be attributed to the enhanced protection provided by the thicker oxide film on the external surface. The deeper distribution of “pores” makes the removal of oxide film from the crevice metal surface more difficult.

3.3. Discussion on the Oxidation Process of FSX-414 Alloy

Based on the above-mentioned evidence, the oxidation mechanism of FSX-414 alloy was investigated, and is illustrated in Figure 12, which could be attributed to two causes. In the early stages of the oxidation, the Cr element endured selective surface segregation due to its high oxygen affinity, preferentially reacting with oxygen to form a continuous and compact protective layer composed of chromium oxide (e.g., 4Cr + 3O2 = 2Cr2O3) [43], as shown in Figure 12a. In addition, at 900 °C, the standard Gibbs free energy of formation for chromium oxide (−818.475 kJ·mol−1) is more negative than those of other oxides (e.g., Ni-O [−132.048 kJ·mol−1], Co-O [−149.363 kJ·mol−1], and W-O [−537.188 kJ·mol−1]) [44]. As a result, the chromium becomes the dominant constituent in the oxide film. The protective layer could effectively inhibit the inward diffusion of the O element, as well as the outward diffusion of the metal elements (e.g., Co2+), thereby impeding the sustained oxidation of the substrate. The growth rate of oxide film decreased while the heating duration exceeded a certain extent, following the law of parabolic [45], which was clearly detected in the decreased growth rate of the narrow crevice with the heating duration from 672 h to 1000 h.
Simultaneously, the W element with a low diffusivity [46] segregated at the oxide/substrate interface, where it oxidized to tungsten oxide (e.g., 2W + 3O2 = 2WO3). Tungsten oxide could not form a solid solution with chromium oxide due to the significant lattice mismatch, which led to the formation of “pores” distributed in the inner metal. The restricted oxygen supply within the narrow crevice results in the smaller and more dispersed “pores” located deeper in the matrix of the narrow crevice compared to those on the matrix of the external surface. As a continuous process of oxidation, channels composed of these “pores” formed between the oxide film and the inner metal, as shown in Figure 12b. Channels composed of tungsten oxides could not only deteriorate the mechanical stability of the oxide layer but also establish a rapid oxygen diffusion region, accelerating localized oxidation [47,48].
The external surface exhibits a thicker oxide film, but with a narrower transition zone between the film and the underlying metal, leading to inferior adhesion. In parallel, tungsten oxidation channels within the interior metal are deeper and more dispersed within the narrow crevice. As a combined result, the surface oxide film within the narrow crevice presents greater difficulty than that of the external surface in removal before welding repair.

4. Conclusions

Narrow crevices and external surfaces of FSX-414 alloy were heated and oxidized at 900 °C for different heating durations up to 1000 h. The growth process and formation mechanism of the oxide films were explored, and the following conclusions were drawn:
(1)
The growth rate of the oxide film on the external surface is slightly larger than that in the narrow crevice, which slowed down after 672 h because of the space-confined geometry and the lower oxygen partial pressure.
(2)
Both oxide films were mainly composed of O and Cr elements, providing protection for the internal metal, leading to a composition transition region between the oxide film and the inner metal.
(3)
The width of the transition region decreased with the heating duration and was smaller on the external surface. This led to a deeper compositional gradient between the oxide film and the inner metal, which in turn facilitated the removal of the oxide during cleaning.
(4)
More “pores” composed of W and O appeared near the oxide films, providing channels between the oxide film and the internal metal, accelerating the localized oxidation as the heating duration increased.
(5)
The depth of the pores was greater within the narrow crevice than on the surface of the metal, which further complicated the removal process.

Author Contributions

Conceptualization, J.W.; methodology, C.Y.; software, Y.Z.; validation, J.L. and Y.G.; formal analysis, Z.G.; investigation, J.W.; resources, J.W.; data curation, C.Y.; writing—original draft preparation, C.Y. and J.W.; writing—review and editing, F.Z.; visualization, C.Y.; supervision, J.Y. and X.G.; project administration, J.W.; funding acquisition, F.Z. and J.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the “National Natural Science Foundation of China, grant number 52305218” and the “Sichuan Science and Technology Program, grant number 2024NSFTD0019”.

Institutional Review Board Statement

No applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article material. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

Authors Junjie Wu, Yingbo Guan Zhenhuan Gao and Xiufang Gong were employed by the company Dongfang Electric Corporation Dongfang Turbine Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Coatings 16 00128 g001
Figure 1. Schematic diagram of the welding process and the welded specimen of FSX-414 alloy. (a) Schematic diagram of the welding process; (b) the upper surface of the welded specimen; (c) the bottom surface of the welded specimen.
Figure 1. Schematic diagram of the welding process and the welded specimen of FSX-414 alloy. (a) Schematic diagram of the welding process; (b) the upper surface of the welded specimen; (c) the bottom surface of the welded specimen.
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Coatings 16 00128 g002
Figure 2. Schematic diagram of the sampling.
Figure 2. Schematic diagram of the sampling.
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Coatings 16 00128 g003
Figure 3. Narrow crevice morphologies and composition of the unoxidized FSX-414 cobalt-based alloy. (a) Crevice width; (b) cross-sectional morphology; (c) element distribution; (d) composition.
Figure 3. Narrow crevice morphologies and composition of the unoxidized FSX-414 cobalt-based alloy. (a) Crevice width; (b) cross-sectional morphology; (c) element distribution; (d) composition.
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Coatings 16 00128 g004
Figure 4. Cross-sectional morphologies and oxide film thickness of the narrow crevice with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f) oxide film thickness.
Figure 4. Cross-sectional morphologies and oxide film thickness of the narrow crevice with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f) oxide film thickness.
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Coatings 16 00128 g005
Figure 5. Line scan images of the cross-section about the narrow crevice and the transition region width with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f): transition region width.
Figure 5. Line scan images of the cross-section about the narrow crevice and the transition region width with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f): transition region width.
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Coatings 16 00128 g006
Figure 6. Area scan images of the cross-section about the narrow crevice preserved for 168 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
Figure 6. Area scan images of the cross-section about the narrow crevice preserved for 168 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
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Coatings 16 00128 g007
Figure 7. Area scan images of the cross-section about the narrow crevice preserved for 1000 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
Figure 7. Area scan images of the cross-section about the narrow crevice preserved for 1000 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
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Coatings 16 00128 g008
Figure 8. Cross-sectional morphologies and oxide film thickness of the external surface with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f) oxide film thickness.
Figure 8. Cross-sectional morphologies and oxide film thickness of the external surface with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f) oxide film thickness.
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Coatings 16 00128 g009
Figure 9. Line scan images of the cross-section about the external surface and the transition region width with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f) transition region width.
Figure 9. Line scan images of the cross-section about the external surface and the transition region width with different heating durations: (a) 168 h; (b) 336 h; (c) 504 h; (d) 672 h; (e) 1000 h; (f) transition region width.
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Coatings 16 00128 g010
Figure 10. Area scan images of the cross-section about the external surface preserved for 168 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
Figure 10. Area scan images of the cross-section about the external surface preserved for 168 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
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Coatings 16 00128 g011
Figure 11. Area scan images of the cross-section about the external surface preserved for 1000 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
Figure 11. Area scan images of the cross-section about the external surface preserved for 1000 h: (a) global; (b) O; (c) Cr; (d) Co; (e) Ni; (f) W.
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Coatings 16 00128 g012
Figure 12. Schematic diagram of the oxidation mechanism for FSX-414 alloy: (a) the formation of oxide film and (b) the formation of channels between the oxide film and inner metal.
Figure 12. Schematic diagram of the oxidation mechanism for FSX-414 alloy: (a) the formation of oxide film and (b) the formation of channels between the oxide film and inner metal.
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MDPI and ACS Style

Wu, J.; Yang, C.; Zhao, F.; Zeng, Y.; Lai, J.; Yu, J.; Guan, Y.; Gao, Z.; Gong, X. Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C. Coatings 2026, 16, 128. https://doi.org/10.3390/coatings16010128

AMA Style

Wu J, Yang C, Zhao F, Zeng Y, Lai J, Yu J, Guan Y, Gao Z, Gong X. Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C. Coatings. 2026; 16(1):128. https://doi.org/10.3390/coatings16010128

Chicago/Turabian Style

Wu, Junjie, Changlin Yang, Fan Zhao, Yi Zeng, Jianping Lai, Jiaxin Yu, Yingbo Guan, Zhenhuan Gao, and Xiufang Gong. 2026. "Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C" Coatings 16, no. 1: 128. https://doi.org/10.3390/coatings16010128

APA Style

Wu, J., Yang, C., Zhao, F., Zeng, Y., Lai, J., Yu, J., Guan, Y., Gao, Z., & Gong, X. (2026). Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C. Coatings, 16(1), 128. https://doi.org/10.3390/coatings16010128

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