# Oxidation induced emissivity variations of the Haynes 25 alloy at high temperatures

M. Balat-Pichelin*, C. Pellegrini, J.L. Sans, E. Bêche

Laboratoire PROMES-CNRS, 7 rue du four solaire, 66120 Font-Romeu Odeillo France

<figure><img src="image_1.png" /></figure>

## ARTICLE INFO

### Keywords:

- Haynes 25
- High temperature oxidation
- Emissivity
- Space debris
- Thruster

## ABSTRACT

Haynes 25 alloy is used in the design of propulsion systems for spacecrafts and it can constitute a space debris at the end of life of the mission. All the thruster combustion chambers and nozzles are manufactured with Haynes 25 alloy and the thrusters used storable monopropellant hydrazine. During the atmospheric reentry of thruster pieces at high velocity, the Haynes 25 alloy is submitted to high temperatures in an extreme environment with atomic oxygen. This is why the high temperature oxidation of Haynes 25 was studied, in air plasma conditions in the temperature range 1000–1700 K. Moreover, as emissivity is an important parameter to know for the heat transfer, the spectral directional emissivity was measured on several samples surfaces: pristine, pre-oxidized in air plasma and in situ oxidized in air. The high temperature oxidation of Haynes 25 is moderate up to 1500 K and above an important mass loss occurred up to 1700 K (around 40 mg/cm²), that is the determined melting temperature. The emissivity of pristine Haynes 25 is very low, around 0.20 at 1350 K and it increases with oxidation up to 0.85–0.90 at 1600 K.

## 1. Introduction

Haynes 25 alloy is the material used in the thruster design for propulsion systems of spacecrafts. It is developed for launch vehicle roll and attitude control systems such as in the Ariane 5 launcher and it is adapted to be implemented for the controlled re-entry of satellites as successfully demonstrated during the ARD (Atmospheric Reentry Demonstrator) mission.

In the literature, there are few studies about the oxidation of Haynes 25 and often at lower temperatures (Tmax = 1473 K) and in different pressure conditions than the ones presented in this work [1–5]. Wolf and Sandrock have shown that the concentration of the minor alloying elements such as silicon and manganese strongly affects the oxidation behavior of Haynes 25 in air, in the temperature range 1273 K to 1473 K up to 225 h [1]. Silicon is also dominant in determining the post-aging ductility of this alloy. They concluded that compositions having silicon concentrations ranging from approximately 0.1 to 0.4 m% and manganese concentrations ranging between approximately 1.4 and 1.65 m% possess both good post-aging ductility and good oxidation resistance. For the studied compositions in Si and in Mn, they always observed a very low mass gain for short oxidation duration at 1373 K. The mass gain for duration of the oxidation test of around 300 s is about 0.18 and 0.30

mg/cm² respectively for 1373 K and 1473 K. The XRD results have shown the formation of oxide scales mainly composed of chromium sesquioxide $Cr_2O_3$ and a spinel phase containing manganese. At the highest temperature, the dominant phases are cobalt monoxide $CoO$ and a spinel probably deficient in manganese. Low concentrations of both silicon and manganese (0.12 m% Si, 1.10 m% Mn) lead to the formation of cobaltous tungstate $CoWO_4$. Angerman had performed oxidation studies on Haynes 25 at 1273 K for different durations (from 1000 to 10 000 h) and at 1423 K during 500 h [2]. He also observed an outer layer of spinel, an inner layer of $Cr_2O_3$ and a zone of globular particles rich in tungsten and silicon. In the alloy depletion zone, the chromium, manganese, and silicon concentrations decreased, but the cobalt, nickel, iron, and tungsten concentrations increased. After 500 h at 1423 K, the outer layer was predominantly composed of $CoO$ with $Co_3O_4$ precipitated along the surfaces of the cracks, at the grain boundaries, and within some of the grains. The other alloying elements were present in solution in minor amounts. The other inner layers were composed of a nearly homogeneous mixture of spinel and $CoWO_4$ with $(Co,Fe)_2SiO_4$ concentrated in alternate layers. Charlot and Westerman have oxidized different alloys among them Haynes 25 up to 1473 K in different atmospheres [3]. If the oxidant pressure is too low, the alloy tends to evaporate, such as for example at $10^{-2}$ Pa for 1473 K. For higher oxidant

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: Marianne.balat@promes.cnrs.fr (M. Balat-Pichelin).</footnote>
<table><caption>**Table 1**
Elementary composition of Haynes 25 (m %).</caption><thead><tr><th>Co</th><th>Cr</th><th>W</th><th>Ni</th><th>Fe</th><th>Mn</th><th>Si</th><th>C</th><th>P</th><th>S</th></tr></thead><tbody><tr><td>balance</td><td>20.31</td><td>15.21</td><td>10.81</td><td>2.50</td><td>1.61</td><td>0.14</td><td>0.113</td><td>0.009</td><td>&lt; 0.002</td></tr></tbody></table>

pressure, the samples have presented spallation when cooled down. At 1473 K, the Haynes 25 samples presented a mass loss during the first minutes of experiments for oxygen pressure of around 330 Pa. Lowell and Deadmore have oxidized Haynes 25 samples at 1373 K up to 100 h for different total air pressures (from 0.13 to $10^5$ Pa) and with water vapor content from 2.5 to 25000 ppm. The formation of a $Cr_2O_3$ oxide layer occurred that breaks down after few hours depending of the moisture content. They have proposed an oxidation model for the protective formation of $Cr_2O_3$ and its breakdown [4]. Recently, Garcia Fresnillo et al. have studied the steam oxidation (Ar-50 % $H_2O$) of Haynes 25 in the temperature range 923–1073 K with exposure time up to 10000 h [5]. For long-term exposure to the steam atmosphere, the Haynes 25 alloy presents the formation of an oxide scale composed of $Cr_2O_3$ and the spinel $MnCr_2O_4$ with very thin silica precipitates at the interface oxide/alloy. Thus a depleted Cr zone exits at the sub-surface in the alloy.

Our study is carried out in very different conditions from the ones found in the literature, as the Haynes 25 samples will be submitted to higher temperatures (up to melting), under atomic oxygen flow and at low total air pressure (2000 Pa) to see if they can be destroyed during the atmospheric re-entry phase on Earth of satellite pieces [6]. The obtained data will be implemented in the database of the European Space Agency through the program ‘Clean Space Initiative’.

## 2. Oxidation at high temperature

In this section, are presented the selected material and the experimental results obtained for isothermal conditions for different holding times and the ones obtained for different temperatures for a constant holding time of around 300 s, corresponding to the maximal duration of a re-entry in the 80–60 km atmosphere.

### 2.1. Materials composition

Haynes 25 is a single phase, cobalt-base and tungsten rich, solid-solution-strengthened alloy. It is stronger than nickel-base solid-solution-strengthened alloys, and is the strongest of the cobalt-base materials that still have good fabrication characteristics. Haynes 25 alloy exhibits good resistance to both air and combustion gas oxidizing environments, and can be used for long-term continuous exposure at temperatures up to 1250 K. For exposure of short duration, Haynes 25 alloy can be used at higher temperatures.

The composition of the Haynes 25 alloy is given in Table 1 (manufacturer data, Haynes Int.) with the main elements: Co, Cr, W and Ni representing 95.63 m% of the composition.

Samples of 15x15 mm², 25 and 40 mm diameter, thickness 2.03 mm were used in this study, respectively for oxidation and emissivity measurement.

### 2.2. Experimental results for the high temperature oxidation and discussion

The oxidation study was conducted in the MESOX facility, described in previous paper, under flowing air plasma conditions on square samples: 15 × 15 mm² with a thickness of around 2 mm [7,8]. The samples are weighed before and after oxidation using a precise balance (Ohaus Adventurer AX224, 0.1 mg accuracy) and the uncertainty of the temperature in the studied range is around 2 %. The oxidation was carried out from 995 K up to 1710 K (≈ T melting) for a holding time of around 300 s at a temperature plateau for a total air pressure of 2000 Pa in a first

<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Photos of two Haynes 25 samples at the melting temperature.</figcaption></figure>

time and then, the oxidation at fixed temperature (around 1570 K, for which the mass loss of the samples is quite important) for different holding times from 50 to 480 s was carried out at the same total pressure in the same air plasma conditions.

To be sure of the normal spectral (5 µm) emissivity to be used to obtain the real temperature using the monochromatic optical pyrometer (temperature error is around 2 %) of the MESOX facility, two samples were brought to melting (Fig. 1). According to the melting temperature, the normal spectral emissivity was fixed at 0.90.

Fig. 2 reports the experimental results for the oxidation carried out during a holding time in plateau of around 300 s and it can be seen that there is nearly no evolution of the mass per unit area from 1000 K up to around 1500 K and then above, the mass of the sample decreases very quickly down to 1700 K. Fig. 3 reports the photos of the samples after oxidation. Even if the mass is constant from 1000 to 1500 K, the surface is oxidized (black color) even if volatile oxides are formed, the mass loss due to volatile species is compensated by the formation of more stable and heavier oxides characterized by XRD (Fig. 4) such as $Cr_2O_3$, CoO and the spinel $CoCr_2O_4$ formed by a very fast reaction between CoO and $Cr_2O_4$ as suggested by Kofstad and Hed [9] and Douglass and Armijo [10]. Above 1500 K, the volatilization of $WO_3$ for the total air pressure of 2000 Pa occurs in agreement with the work of Gulbransen et al. [11]. At the same time, the growing of the chromium tungstate induces a breakdown in the oxide layer, leading to a partial peeling off as it can be seen in Fig. 3.

The samples were characterized before and after oxidation by XRD using a PANalytical X’Pert PRO diffractometer operating at 40 kV and 20 mA (Cu Kα radiation, λ = 0.15418 nm). The X-ray diffraction measurement of θ-θ symmetrical scans was made in the range 10–100°. The step size and the time per step were respectively fixed at 0.01° and 5 s. The X-ray diffraction spectra were recorded with a PANalytical High-Score Plus software. Crystalline phases were identified by comparison with standard reference patterns (Powder diffraction file PDF-2, International Centre for Diffraction data (ICDD)).

Fig. 4 presents the XRD patterns of the non-oxidized sample (reference) and of some samples after oxidation showing the oxide composition with different main compounds according to the temperature level. Around 1000 K, there is nearly no oxidation of the Haynes 25 (ICDD 71–7508). Then, around 1200 K, the main oxide formed is the chromium oxide $Cr_2O_3$ (ICDD 82–1484) but in low quantity as the substrate is still visible in the XRD pattern (peaks around 44° and 51°). By increasing the temperature, around 1400 K, new oxides are present such as the cobalt oxide CoO (ICDD 77–7548) and the mixed spinel oxide $CoCr_2O_4$ (ICDD 80–1668) with still $Cr_2O_3$ in lower quantity. At higher temperature, around 1480 K, the cobalt oxide CoO and the $CoWO_4$ (ICDD 72–0479) tungsten-based oxide are present with the spinel $CoCr_2O_4$. Above 1500
<figure><img src="image_3.png" /><figcaption>Fig. 2. Evolution of the mass variation per unit area versus temperature for the Haynes 25 samples oxidized at 2000 Pa in air plasma conditions.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Fig. 3. Photos of the Haynes 25 samples after oxidation at 2000 Pa under air plasma flow.</figcaption></figure>

K, the spinel CoCr₂O₄ and the CrWO₄ (ICDD 70–2371) tungsten-based oxide are present, the later inducing the breakdown of the oxide layer as suggested by the presence of the peaks of the substrate and also by Espevik et al. who have studied the oxidation of Co-Cr-W alloys at 1523 K [12]. Then, above 1600 K, the oxide layer appears broken as the main peaks of Haynes 25 are clearly visible (around 44° and 51°) and it can be noticed the presence of the iron-based spinel oxide FeCr₂O₄ (ICDD 80–6393) together with the previous ones observed at around 1500 K: the spinel CoCr₂O₄ and CrWO₄.

In a second time, the oxidation at fixed temperature (around 1570 K, for which the mass loss of the samples is quite important as shown in Fig. 2) for different holding times from 50 to 480 s was carried out at a total pressure of 2000 Pa in flowing air plasma conditions. The evolution of the mass variation per unit area as a function of the holding time of oxidation allows obtaining a kinetic law. Fig. 5 reports these data and a kinetic law can be obtained, the mass loss is linearly proportional to the holding time at around 1570 K:

### 3. Emissivity of Haynes 25 alloy, results and discussion

In this section are reported the results obtained for the emissivity of Haynes 25 in high vacuum, measured on pre-oxidized samples and on in situ oxidized ones. The emissivity is measured with a direct method using the MEDIASE facility previously detailed in [13–15]. The

directional spectral radiance of the sample at a fixed temperature and the temperature are measured leading to the determination of the emissivity. The radiance is measured at the center of the sample in a zone of 9 mm diameter at normal incidence. The temperature is the mean value of 6 measurements realized on the horizontal axis passing through the center, each measurement being spaced 1.5 mm apart. We need now to explain how we are making the emissivity measurement. Part of the optical pathway is exposed to the atmospheric environment, such as in between the KRS5 window and the spectroradiometer, there is air on the pathway. The distance between the sample and the spectroradiometer is 104 cm and the part exposed to air is 42 cm. First of all, all the system – goniometer, mirrors, window, spectroradiometer – is calibrated in front of a blackbody in one dedicated room of our lab. Then, the emissivity measurements at high temperature are realized in another location, at the focus of the 1 MW solar furnace so in different conditions of air composition (moisture, temperature, CO₂ level). We acquired during experiment these data in order to compare with the ones measured during the calibration (for these experiments, the temperature was 24 °C and the relative moisture 17 % during the calibration). In the emissivity graphs, the contribution of the absorption bands for H₂O (around 2.7 and 5.2–6.8 µm) and CO₂ (around 2.7 and 4.2 µm) are sometimes visible and we have only suppressed the H₂O contribution around 2.7 µm on the graphs of Figs. 6, 8 and 12. Nevertheless, these small contributions have no effect when calculating the total emissivity
<figure><img src="image_5.png" /><figcaption>Fig. 4. XRD patterns of Haynes 25 (reference, as-received) and oxidized samples at 2000 Pa under air plasma flow.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 5. Evolution of the mass variation per unit area versus holding time for the Haynes 25 samples oxidized at 2000 Pa under air plasma flow at around 1570 K.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Fig. 6. Spectral directional emissivity of a Haynes 25 sample in high vacuum at 1367 K.</figcaption></figure>

<table><caption>**Table 2**
Total hemispherical emissivity of Haynes 25 in high vacuum.</caption><thead><tr><td>P (Pa)</td><td>T(K)</td><td>Total hemispherical emissivity</td></tr></thead><tbody><tr><td>10<sup>-2</sup></td><td>1236</td><td>0.19</td></tr><tr><td>7.3 × 10<sup>-3</sup></td><td>1289</td><td>0.20</td></tr><tr><td>6.0 × 10<sup>-3</sup></td><td>1367</td><td>0.21</td></tr></tbody></table>

<figure><img src="image_8.png" /><figcaption>Fig. 7. Surface roughness of the H25 sample after emissivity measurement in high vacuum.</figcaption></figure>

as they are lower than its standard deviation. The uncertainties of the emissivity change as a function of the temperature and of their spectral and/or directional quantities. The errors on the emissivity values mainly come from the errors on the measured temperature, of the interpolation errors of the function allowing the generation of the reference signal and of the variations of the series of scans of the radiances. For temperatures between 1100 and 1600 K, we typically obtain directional spectral relative uncertainties of 10% at 2 µm, 4% at 10 µm, and 5% for the total hemispherical emissivity.

### 3.1. Emissivity of Haynes 25 alloy in high vacuum

The pyroreflectometer works at 2 wavelengths (1.3 and 1.55 µm). It is calibrated in temperatures and reflectivities. Almost all materials have a reflectivity value at 1.55 µm greater than or equal to that of 1.3 µm. This results in monochromatic temperatures measured at 1.55 µm lower than those measured at 1.3 µm. In rare cases, we have an inversion of reflectivity (R1.3 µm > R1.55 µm) while keeping T1.3 µm > T1.55 µm which makes the calculation of the pyroreflectometric temperature impossible. For the Haynes 25 pristine alloy, it was the case and thus it was only possible to begin the measurement at 1230 K due to the inversion of the reflectivities (at the two wavelengths 1.33 and 1.5 µm) at lower temperatures for the temperature measurement using the pyroreflectometer developed in our laboratory [16]. In Table 2 are reported the results obtained for the total hemispherical emissivity of Haynes 25.

As expected, the total hemispherical emissivity of the Haynes 25 pristine alloy is very low, around 0.20, when it is not oxidized. Fig. 6 presents the evolution of the directional spectral emissivity in high vacuum at 1367 K. The surface roughness parameters, Sq (root mean square surface roughness) and Sz (sum of the largest peak height values and the largest pit depth values within the definition surface area), measured using a 3D profilometry (Leica DCM 3D), up to around 1500 K, were slightly modified with respective values of 0.44 µm and 11.2 µm for the sample before emissivity measurement and 0.44 µm and 17.5 µm after emissivity. Fig. 7 shows the 3D image of the sample surface after the emissivity measurement, which is still very smooth.

In the literature, Deveney in 1967 has reported a value of 0.10 for the total normal emissivity at 833 K [17] that could give a higher value for the total hemispherical emissivity due to the increase of the emissivity at high angles for non-oxidized metals (from 70 to 80°).

### 3.2. Emissivity of Haynes 25 samples oxidized in situ

Del Campo et al. have measured emissivity on brushed, sand-blasted and wire-cut EDM samples but only up to 790 K [18]. The effect of the surface roughness was evidenced, the sand-blasted surface (Ra = 1.6 µm) present a higher emissivity than the brushed one (Ra = 1.2 µm). For the wire-cut EDM (Ra = 2.7 µm), the surface is rougher and probably a little bit oxidized due to the heating of the material due to this technique, so the emissivity is the highest one with values going from 0.80 at 2 µm down to 0.30 at 22 µm.

Three samples (40 mm diameter, 2 mm thickness) were used for the
<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /><figcaption>**Fig. 8.** Spectral directional emissivity for a H25 sample oxidized in situ in flowing air at 2000 Pa for different temperatures: 1111, 1246, 1455 and 1563 K.</figcaption></figure>
<figure><img src="image_12.png" /><figcaption>Fig. 8. (continued).</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>Fig. 9. Total hemispherical emissivity data and linear fits for three H25 samples (Ae, Be and Ce) oxidized in situ in flowing air at 2000 Pa and one (De) at Patm versus temperature.</figcaption></figure>

measurement of the directional spectral emissivity to finally calculate
the total hemispherical emissivity.

Fig. 8 shows for several temperatures the spectral directional

emissivity of Haynes 25 samples during in situ oxidation at 2000 Pa flowing air and Fig. 9 presents the evolution of the total hemispherical emissivity versus temperature for the same samples. During the

<figure><img src="image_14.png" /><figcaption>Fig. 10. Photos of the samples Ae, Be, Ce (2000 Pa) and De (Patm) after emissivity measurement at different temperatures.</figcaption></figure>
<figure><img src="image_15.png" /><figcaption>Fig. 11. XRD patterns of samples Be and De after emissivity measurement.</figcaption></figure>

<figure><img src="image_16.png" /><figcaption>Fig. 12. Normal spectral emissivity for a pre-oxidized H25 sample for two extreme temperatures: 1141 K and 1518 K.</figcaption></figure>

oxidation, it can be seen that the emissivity increases in the far IR range, characteristic of an oxidation process (Fig. 8). It can be also seen that the emissivity increases from 0.25 (close to the value in high vacuum) at around 1100 K showing that Haynes 25 is not yet oxidized at this temperature level. Then, the emissivity increases up to 0.65 around 1300 K

and stays constant up to 1450 K then increases again up to 0.85 at 1600 K. Two laws can be defined for the two temperature ranges for which the total hemispherical emissivity is increasing:

After emissivity measurement, due to the presence of the oxide layer, the surface roughness increases with respective Sq values of 0.90 µm and
<figure><img src="image_17.png" /><figcaption>Fig. 13. Total normal emissivity for three H25 samples pre-oxidized under air plasma flow at 2000 Pa total pressure versus temperature.</figcaption></figure>

16.0 µm for samples Ae and Be, the reference for the non-oxidized sample being 0.44 µm. The difference between Ae and Be is due to the highest temperature level reached during the emissivity measurement with respective values of 1490 K and 1560 K and some places were peeled-off – after cooling down – as shown in the photos of the samples after emissivity (Fig. 10). The sample Ce was heated up to 1590 K. The emissivity of the sample De was measured at atmospheric pressure to see if there is some difference with lower total pressures. As shown in Fig. 9, the evolution of the emissivity versus temperature is the same for all the samples oxidized, at 2000 Pa or at atmospheric pressure, and for example, the samples Be and De both show the mixed spinel oxide CoCr₂O₄ (ICDD 80–1668) together with the tungsten-based oxides CoWO₄ (ICDD 72–0479) and CrWO₄ (ICDD 70–2371) in different proportions as confirmed by XRD (Fig. 11). Some peaks of FeCr₂O₄ (ICDD 80–6393) are also visible on the pattern of samples Be and De (open). As some peeling-off has occurred on the surface, the diffraction peaks (43.8, 51.1 and 75.1°) are attributed to the substrate H25 alloy (black dots in Fig. 11).

### 3.3. Emissivity of pre-oxidized Haynes 25 samples in air plasma

Three H25 samples were pre-oxidized in the MESOX set-up in the same conditions as previously mentioned for the oxidation: 2000 Pa total pressure, air plasma, 300 W microwave, 4 l/h air flow and for maximal temperatures of 1570 K for A, 1535 K for B and 1580 K for C. Fig. 12 presents the normal spectral emissivity for two extreme temperatures: 1141 and 1518 K and the trend is characteristic of the presence of an oxide layer with high emissivity in the far IR range. In Fig. 13 is presented the evolution of the total normal emissivity versus temperature. The emissivity is noted ‘up’ during the increase in temperature and ‘down’ during cooling down to show that the oxide layer remains on the surface with few modifications as nearly same values are measured for the emissivity. The total normal emissivity is increasing from 0.70 at around 1150 K up to 0.85 at around 1600 K.

The surface roughness was slightly modified after the emissivity measurement: for example, for sample A, with respective Sq values after oxidation in MESOX (so before emissivity measurement) and after emissivity measurement of 3.26 µm and 3.79 µm, this difference being not enough important to have a sensitive effect on the emissivity.

Our results are in good agreement with the ones of Wade that

measured a total hemispherical emissivity on stabilized oxide layers developed on Haynes 25 of 0.85 to 0.89 from 588 K to 1366 K [19]. In the same way, Deveney has obtained a total normal emissivity of 0.90 up to 1556 K in a simulated re-entry environment on oxidized surfaces [17].

### 4. Conclusions

The oxidation of Haynes 25 samples was studied from 1000 K up to the melting temperature of around 1700 K in low total air pressure conditions at 2000 Pa to simulate an atmospheric entry of a space debris. No evolution of the mass per unit area from 1000 K up to around 1500 K were detected, even if volatile oxides are formed and thus, the mass loss due to volatile species is compensated by the formation of more stable and heavier oxides characterized by XRD. Then above this temperature, the mass of the sample decreases very quickly down to 1700 K with some peeling-off of the oxide layers. The emissivity of Haynes 25 samples: as-received (pristine), pre-oxidized in air plasma and oxidized in situ in air was measured from 1000 K up to 1600 K in different atmospheres: high vacuum, for a low total air pressures of 2000 Pa concerning the aerospace domain and at atmospheric pressure. New experimental results obtained for this material at high temperatures and different pressure conditions together with microstructural characterization using XRD and 3D profilometry were obtained as no data was found in the literature at such high temperatures. As expected, the emissivity of the oxidized Haynes 25 samples is much higher than the one measured in high vacuum due to the presence of the oxide layer and there is no difference between air plasma and standard air conditions – in reduced atmospheres of 2000 Pa or at atmospheric pressure – with an emissivity increase by a factor 4 in comparison with the pristine material. It was also shown that the most important parameter increasing the emissivity is the presence of the oxide layer that also increases the surface roughness whatever the chemical composition.

### Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
## Data availability

Data will be made available on request.

## Acknowledgements

The authors thank the European Space Agency (ESA) for the partial funding of this study through the contract with RTech (CNRS n° CT239424) and the programme "Investissements d'Avenir" (Investment for the Future) of the Agence Nationale de la Recherche (National Agency for Research) of the French State under awards numbers ANR- 10-EQPX-49-SOCRATE.

## References

[1] J.S. Wolf, G.D. Sandrock, Some observations concerning the oxidation of the cobalt-base superalloy L-605 (H25), NASA TN D-4715, August 1968.

[2] C.L. Angerman, Long-term oxidation of superalloys, Oxid. Metals 5 (2) (1972) 149-167.

[3] L.A. Charlot, R.E. Westerman, High temperature corrosion of candidate ATR structural materials, BNWL-100 report, Sept. 1965, Battelle-Northwest, Richland, Washington.

[4] C.E. Lowell, D.L. Deadmore, Formation and breakdown of a protective layer of chromium sesquioxide on L-605 alloy at 1100°C, Oxid. Metals 7 (1) (1973) 55-69.

[5] L. Garcia Fresnillo, A. Chyrkin, T. Hüttel, C. Böhme, J. Barnikel, D. Grüner, F. Schmitz, W.J. Quadakkers, Oxide scale formation and subsurface phase transformations during long-term steam exposure of the cobalt base alloy 25, Mater. Corr. 63, 2012, n°9999.

[6] Y. Prévereaud, J.L. Vérant, M. Balat-Pichelin, J.M. Moschetta, Numerical and experimental study of the thermal degradation process during the atmospheric re-entry of a TiAl$_{6}$V$_{4}$ tank, Acta Astron. 122 (2016) 258-286.

[7] M. Balat-Pichelin, L. Barka, Behavior of TA6V alloy at high temperature in air plasma conditions - Part 1: oxidation, J. Mater. Eng. Perf. 29 (7) (2020) 4597-4605.

[8] M. Balat-Pichelin, J.L. Sans, E. Bèche, V. Flaud, J. Annaloro, Oxidation and emissivity of Inconel 718 alloy as potential space debris during its atmospheric entry, Mater. Charac. 127 (2017) 379-390.

[9] P.K. Kofstad, A.Z. Hed, Oxidation of Co-25w/o Cr at high temperatures, Journal of the Electrochemical Society 116 (11) (1969) 1542-1549.

[10] D.L. Douglass, J.S. Armijo, The influence of manganese and silicon on the oxidation behavior of Co-20Cr, Oxid. Metals 3 (2) (1971) 185-202.

[11] E.A. Gulbransen, K.F. Andrew, F.A. Brassart, Kinetics of oxidation of pure tungsten, 1150°-1615°C, Journal of the Electrochemical Society 111 (1) (1964) 103-109.

[12] S. Espevik, R.A. Rapp, P.L. Daniel, J.P. Hirth, Oxidation of ternary Co-Cr-W alloys, Oxid. Metals 20 (1/2) (1983) 37-65.

[13] M. Balat-Pichelin, J. Annaloro, L. Barka, J.L. Sans, Behavior of TA6V alloy at high temperature in air plasma conditions - Part 2: thermal diffusivity and emissivity, J. Mater. Eng. Perf. 29 (7) (2020) 4606-4616.

[14] M. Balat-Pichelin, J.L. Sans, E. Bèche, L. Charpentier, A. Ferrière, S. Chomette, Erratum to 'Emissivity at high temperature of Ni-based superalloys for the design of solar receivers for future tower power plants' [Solar Energy Mater. Solar Cells 227, 111066] Solar Energy Mater, Solar Cells 230 (2021) (2021), 111228.

[15] M. Balat-Pichelin, J.L. Sans, E. Bèche, Spectral directional and total hemispherical emissivity of virgin and oxidized 316L stainless steel from 1000 to 1650 K, Infrared Phys. Tech. 123 (2022), 104156.

[16] D. Hernandez, J.L. Sans, A. Netchaieff, P. Ridoux, V. Le Sant, Experimental validation of a pyroreflectometric method to determine the true temperature on opaque surface without hampering reflections, Measurement 42 (2009) 836-843.

[17] J.E. Deveney, Emittance value of Haynes 25 for a selected reentry environment, Report SC-RR-66-576, Sandia Laboratory, Albuquerque, 1967.

[18] L. Del Campo, R.B. Perez-Saez, L. Gonzalez-Fernandez, X. Esquisabel, I. Fernandez, P. Gonzalez-Martin, M.J. Tello, Emissivity measurements on aeronautical alloys, J. Alloys Comps 489 (2010) 482-487.

[19] W.R. Wade, Measurements of total hemispherical emissivity of several stably oxidized metals and some refractory oxide coatings, NASA MEMO 1-20-59L (1959).