Short-term Oxidation Research Articles

Short-term oxidation and residual compression properties of needle-punched carbon/carbon composites

Needle-punched carbon/carbon (NP C/C) composite is widely used in rocket-engine nozzles and re-entry vehicles. Recyclable technology expedited the research on repeated oxidation and residual mechaincal properties of thermal-protection materials. In this study, the critical longitudinal compression strengths before and after oxidation are derived based on the Timoshenko beam theory. Three repetitions of short-term oxidation cycles and compression experiments are investigated. The average oxidation rate of this composite was 5∼6% in 10 min and kept linear increase. In-plane and out-of-plane compressive strengths of NP C/C composite diminish quasi-linearly due to oxidation at 1000°C, with their moduli decreasing in a periodically slow-sharp pattern. After three oxidation cycles, the levels of residual in-plane modulus and strength were 55.20% and 56.89%, respectively, while the resudual out-of-plane modulus and strength were 44.65% and 47.23%, respectively. The results showed that the material exhibited the pesudo-plastical behaviour after oxidation, cracks grew along the punched conical structures formed by the punching technology. In-plane and out-of-plane modulus were more sensitive than their strengths after first oxidation cycle.

Short-term oxidation behavior of powder metallurgy Al0.8Co0.5Cr1.5CuFeNi HEA in high-temperature solid and semi-solid intervals

In this work, possible short-term thermal exposure oxidation in hot processing including semi-solid processing is focused. We aim to investigate the short-term oxidation behavior of a novel powder metallurgy Al0.8Co0.5Cr1.5CuFeNi high entropy alloy (HEA) in high-temperature solid (1000–1100 °C) and semi-solid (1125–1225 °C) intervals. From 1000 to 1225 °C, mass gain increases from 0.31 to 0.45 mg cm–2 after 60 min oxidation, presenting superior oxidation resistance in the semi-solid state compared with other semi-solid alloys. Equiaxed α-Al2O3 grains are the predominant component of oxide scales and no obvious internal oxidation layer occurs in both solid and semi-solid intervals. Al2O3 scale growth is predominantly determined by outward Al3+ diffusion. For solid oxidation, different scale formation kinetics occur on various phases and the BCC(B2) phase has faster scale formation kinetics. This is attributed to outward Al3+ diffusion rate differences in various component systems. During semi-solid oxidation, the increased degree of chaos and number of vacancies in the liquid phase provide a diffusion channel, leading to rapid Al2O3 formation. Oxidation resistance in the semi-solid state is attributed to dense Al2O3 scales formed through selective oxidation of Al.

High temperature and short-term oxidation behavior of a TiBw/TA15 network composite in an air environment at 950 °C

The oxidation behavior of materials used in aerospace is crucial for their service life, and short-term oxidation behavior is an essential means to reveal the oxidation mechanism. The high temperature and short-term oxidation behavior of the TiBw/TA15 network composite in an air environment at 950 °C for 5 min, 15 min, 30 min, and 60 min was investigated. The experimental result indicates that the composite shows a slight mass change over the whole test times. The all-oxide scale mainly contains two-layer. From the top to the bottom of the oxide scale, an Al2O3 layer and a TiO2 layer existed, which increased with the oxidation time. The oxidation mechanism of the initial oxidation behavior of the network composite has been established, which is crucial for promoting its application in high-temperature service environments.

The Adhesion and Moisture Damage Resistance between Castor Oil-Based Bio-Asphalt and Aggregates under the Action of Thermal-Oxidative Aging

This study aims to investigate the adhesion properties and moisture damage resistance between castor oil-based bio-asphalt (COBA) and aggregates under the action of thermal oxidation. Different dosages of castor oil-based bio-oil (5%, 10%, and 15%) were used to prepare the COBA by mixing it with petroleum asphalt. The short-term and long-term aging of COBA were simulated by the rolling thin-film oven test (RTFOT) over 85 min and 385 min, respectively. The boiling method, photoelectric colorimetry, contact angle test, and contact angle moisture susceptibility test (CAMSI) were used to evaluate the adhesion and exfoliation of the COBA–aggregates before and after thermal oxygen aging. Then, the aging degree of COBA was quantitatively evaluated by Fourier transform infrared (FTIR), and the correlation between aging condition and COBA–aggregates adhesion was analyzed. The results showed that the cohesion in COBA increased by 23.1% on average due to the addition of bio-oil. And the adhesion between COBA and aggregates increased by 5% due to the acidic compounds formed in the process of interaction with silicates on the surface of the aggregates. After short-term thermal oxidation, the adhesion between COBA and its aggregates was further improved as the polar components in the asphalt binder increased when the bio-oil dosage was less than 10%. However, with the continuous increase in the bio-oil amount and thermal oxidation degree, the adhesion decreased by 12.6% when compared to the virgin status; in addition, the adhesion grade decreased. Also, a low dosage of bio-oil was found to also improve COBA’s resistance to moisture damage, and helped to reduce moisture sensitivity during the interaction with asphalt binder. However, the acidic compounds that were generated by the reaction with hydrolyzed aggregates in the presence of asphalt binder reduced the adhesion between COBA and the aggregates. Finally, FTIR revealed a good correlation between IC=O and adhesion between COBA and the aggregates.

Distinctive performance evolution of surface layer in TC4 alloy oxidized at high temperature: Softening or hardening?

The characteristics of metal surface layer at high-temperature significantly affect the service performance of TC4 titanium alloy components, so that the evolution mechanism of mechanical properties of metal surface layer under high-temperature oxidation conditions is an important scientific issue. In the present work, the mechanical behavior and the relevant mechanism of metal surface oxidized at the temperatures of 500 ℃, 700 ℃, and 900 ℃ for different times have been systematically investigated. The experimental results show that with the increase of temperature, the oxidation kinetics curve of the alloy changes from parabolic law to linear law, and the oxidation reaction changes from diffusion control to interfacial reaction control. Furthermore, as the temperature increases from 500 °C to 900 °C, the feature of oxide scale changes from the single-layer structure to the multi-layer alternating structure, and the thickness of oxide scales and depth of alpha case increased with increasing temperature. The surface oxide scale is mainly composed of low valent oxides such as Ti3O and Ti6O during low-temperature oxidation as well as short-term high temperature oxidation. After long-term high temperature oxidation, the oxide scale is mainly composed of high valent oxides such as TiO2, Al2O3, and TiVO4. Simultaneously, significant changes occur in the composition, microstructure and properties of metal surface layer. In general, the microstructure and mechanical properties of the surface-layer metal are strongly dependent upon the competitive influence of the outward diffusion of Al and the inward diffusion of O. In the temperature range of 500–900ºC, when the temperature is relatively low, the softening effect caused by the outward diffusion of Al is stronger than the strengthening effect caused by the inward diffusion of O, and a surface softening effect thus occurs. On the contrary, when the temperature is high, the strengthening effect caused by the inward diffusion of O is stronger than the softening effect caused by the outward diffusion of Al, and a surface strengthening effect accordingly happens.

Nonmicrobial mechanisms dominate the release of CO2 and the decomposition of organic matter during the short-term redox process in paddy soil slurry

Both biotic and abiotic mechanisms play a role in soil CO2 emission processes. However, abiotically mediated CO2 emission and the role of reactive oxygen species are still poorly understood in paddy soil. This study revealed that OH promoted CO2 emission in paddy soil slurries during short-term oxidation (4 h). OH generation was highly hinged on active Fe(II) content, and the OH contribution to CO2 efflux was 10%–33% in topsoil and 40%–77% in deep-soil slurries. Net CO2 efflux was higher in topsoil slurries, which contained more dissolved organic carbon (DOC). CO2 efflux correlated well with DOC contents, suggesting the critical role of DOC. Microbial mechanisms contributed 9%–45% to CO2 production, as estimated by γ-ray sterilization experiments in the short-term reoxidation process. Solid-aqueous separation experiments showed a significant reduction in net CO2 efflux across all soil slurries after the removal of the original aqueous phase, indicating that the water phase was the main source of CO2 emission (>50%). Besides, C emission was greatly affected by pH fluctuation in acidic soil but not in neutral/alkaline soils. Fourier transform ion cyclotron resonance mass spectrometry and excitation-emission matrix results indicated that recalcitrant and macromolecular dissolved organic matter (DOM) components were more easily removed or attacked by OH. The decrease in DOM content during the short-term reoxidation was the combined result of OH oxidation, co-precipitation, and soil organic matter release. This study emphasizes the significance of the generally overlooked nonmicrobial mechanisms in promoting CO2 emission in the global C cycle, and the critical influence of the aqueous phase on C loss in paddy environments.

Improved oxidation resistance of ODS-CrFeNi medium entropy alloys by different Y2O3/Ti/Zr additions

Isothermal oxidation tests of four types of oxide dispersion strengthened (ODS)-CrFeNi medium entropy alloys (MEAs) with different Y2O3/Ti/Zr additions, i.e., 1Y alloy (Y2O3), 1YT (Y2O3/Ti), 1YZ (Y2O3/Zr), and 1YTZ (Y2O3/Ti/Zr), were conducted at 1000 ℃ and 1100 ℃ for 12 h to explore the effects of oxide-forming elements on the high-temperature short-term oxidation resistance. XRD, SEM and EDS analyses were performed to characterize the microstructure and phase composition of the oxide layers of the four alloys at different oxidation temperatures. The results showed that the surface oxide layers formed on all ODS-MEAs are mainly composed of hexagonal Cr2O3. The thickness and defects (e.g. pores and microcracks) of the oxide layer strongly depend on the Y2O3/Ti/Zr additions and the oxidation temperature. In general, the thickness of the oxide layer increases with increasing temperature. The oxide layer on 1YZ alloy is very dense and the thickness hardly changes with increasing temperature (0.8 µm at 1000 °C and 0.9 µm at 1100 °C), which exhibits the best oxidation resistance and is comparable to that of ODS-FeCrAl. However, 1YTZ alloy shows the worst oxidation resistance at both 1000 ℃ and 1100 ℃. The oxide layer is loose together with many pores and microcracks, and the thickness is the thickest among the four alloys. In addition, severe internal oxidation occurs in 1YTZ, which is not obviously observed in the other three alloys. The excellent oxidation tolerance of 1YZ is due to the addition of Zr, which results in the formation of thermodynamically stable oxides Y4Zr3O12, which has the highest number density and smallest oxide size among the four alloys. High-density interfaces between the oxides and the matrix effectively slow down the inward diffusion rate of O and the outward diffusion rate of Cr, and inhibit/moderate the coarsening of the oxides and the formation of volatile CrO3. Therefore, pores and microcracks are effectively suppressed in Zr-containing 1YZ.

Effects of oxidation degree and antioxidant addition on the carbon deposition tendency of jatropha biodiesel

ABSTRACT The residual carbon value and existent gum content were used to evaluate the carbon deposition tendency of the jatropha biodiesel with different oxidation degrees. The chemical components of residual carbon and existent gum of the jatropha biodiesel were analyzed before and after oxidation by Gas chromatography-mass spectrometry (GC-MS) and infrared spectrometer. The results showed that in the short-term oxidation process, both the residual carbon and existent gum content decreased first, and then increased with oxidation time. In the long-term oxidation process, these two indicators monotonically increased with oxidation time. The residual carbon and existent gum content increased from 1140 mg/100 mL to 11,300 mg/100 mL and from 0.0272% to 0.277%, respectively. After oxidation, the aromatic compounds in the residual carbon as well as the content in the existent gum such as cyclic ether, carboxylic acid, ketone carbonyl and some fat-soluble impurities significantly increased. The addition of antioxidants showed inhibitive effect on the formation of carbon residue and existent gum. Butylated hydroxytoluene reduced the gum content by 58.3%, and methyl gallate reduced the residual carbon value by 21.1%. These findings prove that the antioxidants can effectively inhibit the auto-oxidation of biodiesel, and thus, reduce the carbon deposition tendency of biodiesel.

A comparative study on the surface degradation mechanisms of arc melted and laser remelted CoCrFeNiAl0.5Nb0.5 HEA

In the current study, a CoCrFeNiAl0.5Nb0.5 high entropy alloy was manufactured via arc melting and exposed to laser surface remelting. The presence of Nb and Al was limited to the formation of single simple cubic phase formations. Both alloys are composed of four phases. Laser remelting did not change current phases, but it affected the microstructure. Hardness increased from 475 HV to 785 HV thanks to the change in phase ratios and grain refinement resulting from laser remelting. Wear resistance improved due to the increase in hardness, and volume losses decreased by 28 %. In short-term high-temperature oxidation, laser remelting enabled better oxidation resistance in alloy since it provided more paths for the diffusion of aluminum, which forms an alumina oxide scale. Interestingly, such a trend was not observed in the increased oxidation period. In the final oxidation stage, the depletion of B2 phases and the formation of inner oxides significantly worsened the oxidation resistance of LR alloy. Although Icorr, which expresses the corrosion resistance of the laser-melted alloy, was higher than before the laser-remelting process, the changes in the alloy's microstructure with rapid cooling caused a decrease in the passivation resistance of laser-remelted CoCrFeNiAl0.5Nb0.5 HEA.

Evaluation of Short-Term Oxidation Mechanism of Laser Cladded Ni–Cr–C Coating on Titanium Aluminide Substrate

In the present investigation, a NiCr–Cr3C2 powder mixture was deposited on titanium aluminide substrate by laser cladding. The kinetics and mechanism of oxidation of the substrate and coating were studied at 800–1100 °C using XRD, SEM, ToF–SIMS and XPS characterization techniques. The results demonstrated that the Ni–Cr–C coating had improved oxidation resistance, as compared to the substrate. The oxidized surface of the coating was covered with Cr2O3 and NiCr2O4 phases at the early stages of the oxidation. The formation of NiCr2O4 could be attributed to the reaction of NiO (an oxidation product of the NiCr phase) and Cr2O3 (an oxidation product of the chromium carbide phase) during oxidation. Increasing the oxidation time at 900 °C led to the partial formation of CrO3 as a result of the oxidation of Cr2O3. It was also found that the parabolic rate constant ratio of $$\left( {K_{{\text{p}}}^{{{\text{substrate}}}} /K_{{\text{p}}}^{{{\text{coating}}}} } \right)$$ increased with the temperature, which showed, comparatively, the better oxidation resistance of the coating at higher temperatures.

Intermetallic phase precipitation and oxidation behavior of Fe–20Cr–0.5Nb–2Mo (at%) high-Cr ferritic alloy at high temperatures

The precipitation behavior of intermetallic compounds, such as C14 Laves phase and Chi (χ) phase, and oxidation behavior of an Fe–20Cr–0.5Nb–2Mo (at%) high-Cr ferritic alloy were investigated at high temperatures between 1023 K and 1123 K. During aging/oxidation heat treatment at 1073 K, the protective Cr2O3 is rapidly formed on the surface, consecutively, a high density of fine Laves precipitates, (Fe,Cr)2(Mo,Nb), are formed throughout the α-Fe matrix and preferably at the α/Cr2O3 interfaces as well as α-Fe grain boundaries. The Laves precipitation causes local changes of solute concentrations in the surrounding α-matrix, i.e., decrease in Nb and increase in Mo. These local changes of phase equilibria in the vicinity of the α-grain boundaries and α/Cr2O3 interfaces result in the formation of the χ-phase which is not supposed to be precipitated. Moreover, χ precipitation at the α/Cr2O3 interfaces is most favored in case the alloy is oxidized at 1073 K. In the short-term oxidation at 1073 K, the Cr-rich χ interfacial precipitates, Fe36Cr12(Mo8,Nb2), suppress the growth of Cr2O3. However, as the interfacial χ precipitates coarsen in the long-term oxidation at 1073 K, localized stress concentrations are generated at intersections between the Cr2O3 layer and the α/χ interfaces. Consequently, these facilitate cracking of the adjacent surface oxide, then oxide ‘rehealing’, and formation of the abnormal-Cr2O3 process. Eventually, the precipitation of interfacial χ phase indirectly causes an acceleration growth of the surface Cr2O3 on the alloy.

Use of Multi-Scale Investigation to Evaluate Adhesion Performance of Warm-Mix Polymer-Modified Asphalt

Warm Mix Asphalt (WMA) technology can effectively reduce carbon emissions and energy consumption during road project construction. However, it may have a negative impact on the binding properties of asphalt mixtures. In order to effectively evaluate the adhesion performance of asphalt binders and aggregates under the combined influence of WMA and traditional polymer-modified asphalt, this paper provides a comprehensive evaluation at the micro and macro levels. The adhesion between three different modified asphalts (warm mix crumb rubber/ Styrene-Butadiene-Styrene (SBS) composite modified asphalt, warm mix crumb rubber asphalt, and warm mix SBS modified asphalt) and two different aggregates (limestone and granite) under both virgin and short-term aging conditions were analyzed. Regardless of the type of modified asphalt, the results showed that limestone aggregates have better adhesion properties with asphalt binders. In addition, the short-term thermal oxidation aging behavior is conducive to enhancing the asphalt-aggregate adhesion characteristics. Furthermore, WMA additives, crumb rubber, and SBS compound modification can improve the adhesion performance between asphalt and aggregate.

Short-term isothermal oxidation of hot extruded GH3536 Ni-based superalloy in solid and semi-solid temperature ranges

The short-term isothermal oxidation process of hot extruded GH3536 alloy in solid and semi-solid temperature ranges was investigated. The solid oxidation rates at 1200 °C, 1250 °C, 1300 °C were 0.049 mg2cm−4s−1，0.125 mg2cm−4s−1, 0.133 mg2cm−4s−1 respectively, while semi-solid oxidation rates at 1350 °C, 1360 °C, 1367 °C were 0.168 mg2cm−4s−1，0.259 mg2cm−4s−1，0.549 mg2cm−4s−1 respectively. Oxide scales formation and spallation were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS). The outer diffusion of Cr3+and Fe3+resulted in formation of Fe2O3 and Cr2O3 granular oxides. Diffusion of Ni2+ promoted spinel formation. NiO intermediate oxidation layer was formed beyond 1300 °C, which was conducive to continuous Cr2O3 inner oxidation layer formation. The growth and spallation of oxide scales were significantly accelerated during semi-solid oxidation. The liquid film in the semi-solid microstructure provided a diffusion channel. The inner oxidation layer was destroyed due to thermal stress and severe deformation of the interface between oxide scales and base alloy, which led to a sharp increase in oxidation rate.

Short-term oxidation behavior of 304 stainless steel in N2-21 vol％O2 environment between 900 and 1200 °C

Oxidation behavior and microstructure evolution of 304 stainless steel at 900–1200 °C in N2-21 vol％O2 were investigated. At 900 °C, Cr2O3 protective oxide is formed on the surface of the steel. With the increase in temperature (1100 °C), an inner oxide layer is formed consisting of two phases (Fe, Cr)3O4 oxide and remaining Ni-Fe metallic. The oxide scale formed at 1200 °C has a unique morphology consisting of the inner Cr-rich oxidation region, middle gap region, outer porous Fe3O4 oxide region, and outermost dense Fe2O3 oxide scale. A discontinuous SiO2 layer appears in the oxide scale.

High-temperature oxidation performance of Ni-based GH3536 superalloy fabricated by laser powder bed fusion

This study investigates the effect of microstructure on short-term and long-term oxidation behaviours of GH3536 superalloy fabricated by laser powder bed fusion (LPBF), in which the superalloy is isothermally oxidised at 950 °C for 6 h and 500 h in air. The LPBF sample exhibits improved oxidation resistance compared with a wrought counterpart after long-term exposure. The effect of microstructure diversity between LPBF and wrought samples on oxidation behaviour is discussed. The cellular structure produced during the LPBF process acts as a rapid diffusion path to accelerate the formation of a protective film in the initial stage, leading to an enhancement in oxidation resistance for extended exposure.

Improving the high-temperature oxidation resistance of Fe-18Cr-8Ni austenitic stainless steel by cold-rolling treatments

The effect of different degrees of cold rolling on the short-term oxidation behavior of Fe-18Cr-8Ni stainless steel oxidized at 1000 °C in N2-21 vol%O2 for 3 h was investigated. The results show that cold rolling deformation reduces the grain size and coincident site lattice (CSL) grain boundary fraction of the alloy. When the deformation exceeds 20%, the oxidation mechanism changes from internal to external oxidation. And the critical concentration of Cr and Si required for forming the protective oxide scale decreases. The formation of continuous Cr2O3 and SiO2 layers on the alloy prevents the diffusion of oxygen from the surface to the matrix. The cold-rolling treatments improve the oxidation resistance of the Fe-18Cr-8Ni austenitic stainless steel at 1000 °C.

Comparative investigation of different blends ageing behaviours for short-term thermal oxidation ageing mechanism of SBS-modified bitumen

Instead of styrene-butadiene-styrene triblock copolymer (SBS) modified bitumen (SBSMB) being taken as a whole to be investigated in most of previous aging mechanism studies, the respective contributions of SBS and bitumen matrix to SBSMB aging behavior were evaluated in this research. Four bituminous samples including the blend of aged SBS with fresh bitumen matrix (TAS+B), the blend of un-aged SBS with aged bitumen matrix (S+TAB), un-aged and short-term aged SBSMB, were prepared and then compared in terms of physical and rheological properties, molecular size and morphological polymer phase structure. The results indicate the thermal degradation of copolymer and the aging hardening of bitumen matrix jointly determine the SBSMB aging behaviors. The bitumen matrix aging effect outweighs the copolymer aging effect in view of ductility, viscosity and complex modulus results, and the quantitative relationship formulated between these two effects is valid in some cases.

Short-Term Oxidation Behavior, Microstructure Evolution and Compression Behavior of Nickel-Based Superalloy GH4037 in Solid and Semi-Solid States

Semi-solid processing combines the advantages of traditional forging and casting methods, so it has received much attention recently. However, the research on semi-solid behaviors of Nickel-based superalloys has been rarely reported. In order to investigate the behaviors of Nickel-based superalloy at solid and semi-solid states, oxidation experiments, isothermal treatment experiments and deformation experiments of GH4037 alloy were studied. Short-term oxidation experiments of GH4037 alloy were carried out at a solid temperature (1200 °C) and a semi-solid temperature (1360 °C). The results indicated that the oxides formed at 1200 °C were mainly composed of TiO2, Cr2O3 and a small amount of spinels NiCr2O4, while the oxides formed at 1360 °C consisted of the spinels of NiCr2O4, NiWO4 and NiMoO4 besides TiO2 and Cr2O3. Microstructure evolution of GH4037 alloy after semi-solid isothermal treatment at 1370 °C and 1380 °C was studied. The results indicated that semi-solid microstructures consisted of equiaxed solid grains and liquid phases. The average grains size and shape factor of solid grains were affected by melting mechanism and grain growth mechanism. Compression behaviors of GH4037 alloy after compressed at 1200 °C and 1360 °C were investigated. The results indicated that the flow stress of 1360 °C decreased significantly compared to that of 1200 °C. The deformation zones in the specimens were divided into three parts: the difficult deformation zone, the large deformation zone, and the free deformation zone. At 1200 °C, the deformation mechanism was plastic deformation mechanism. At 1360 °C, sliding between solid particles (SS), liquid flow (LF), flow of liquid incorporating solid particles (FLS), plastic deformation of solid particles (PDS) coexisted in the compression specimen.

Short-Term Isothermal Oxidation of Hot Extruded Gh3536 Ni-Based Superalloy in Solid and Semi-Solid Temperature Ranges

Short-Term Isothermal Oxidation of Hot Extruded Gh3536 Ni-Based Superalloy in Solid and Semi-Solid Temperature Ranges

The interaction between Dy, Pt and Mo during the short-time oxidation of (γ’ + β) two-phase Ni Al coating on single crystal superalloy with high Mo content

Mo, as a typical refractory element in Ni-base superalloys , will diffuse outward to the protective coating on the alloy surface during high-temperature oxidation, which will do harm to mechanical properties of the alloy and oxidation resistance of the coating. In this paper, (γ’ + β) two-phase Ni-34Al-0.3Dy coatings with or without Pt were prepared on a single crystal superalloy with high Mo content by electron beam physical vapor deposition (EB-PVD) and Pt electroplating. The short-term oxidation behavior of the coatings was investigated at 1100 °C aiming to explore the role of Dy and Pt on the harmful effect of Mo diffusion and its oxides. The results show that for Pt-free coating, Mo had already diffused to the coating surface after only 1 h. The pre-existing Dy 2 O 3 would react with MoO 3 to form Dy 2 MoO 6 thus suppressed the volatilization of MoO 3 at the early stage of oxidation. However, as the oxidation proceeded, Dy 2 MoO 6 would decompose due to its poor thermal stability. While for Pt-doped coating, no Mo-rich oxides were detected throughout the entire oxidation process due to the suppression of outward Mo diffusion by the Pt layer at coating/substrate interface. The possible mechanisms were discussed in detail. • Pt-free/doped (γ’ + β) NiAlDy coatings are prepared on IC21 with high Mo content. • The role of Dy and Pt on suppressing the formation of harmful MoO 3 is focused on. • Dy delays volatilization of MoO 3 by forming Dy 2 MoO 6 which is not completely stable. • Pt inhibits diffusion of Mo by enhancing Al content in Pt-rich layer at interface. • Weak inter-attraction between Pt and Mo contributes to the Mo diffusion inhibition.