Isothermal Oxidation Resistance Research Articles

The improvement in high-temperature oxidation resistance of Ni0.25Co0.25Cr0.22Mo0.14Re0.14 high entropy alloy via industrial chemical vapor aluminizing process

The effects of the protective coating (NiAl coating) on the high temperature isothermal oxidation resistance of Ni0.25Co0.25Cr0.22Mo0.14Re0.14 high entropy alloy (HEA) was discussed in this work. A nickel aluminide (NiAl) coating was obtained on the Ni0.25Co0.25Cr0.22Mo0.14Re0.14 HEA via the industrial chemical vapor aluminizing (CVA) process. Isothermal oxidation tests were applied to NiAl-coated and uncoated samples in ambient laboratory air for durations of up to 200 h at 1050 °C to investigate the effects of the NiAl coating on high-temperature isothermal oxidation resistance of Ni0.25Co0.25Cr0.22Mo0.14Re0.14 HEA. The results revealed that a protective and slowly growing α-Al2O3 oxide layer formed on the surface of the NiAl-coated HEA samples and remained stable even after 200 h of isothermal oxidation. For uncoated HEA samples, not only Cr2O3 but also non-protective spinel oxides (CoCr2O4 and NiCr2O4) were detected on the surface. Weight gain was observed in the NiAl-coated HEA samples due to the formation of a protective and slowly growing α-Al2O3 oxide layer on the NiAl coating. In contrast, the uncoated HEA samples experienced weight loss even after 6 h of isothermal oxidation, as Cr2O3 lost its stability at 1050 °C and non-protective spinel oxides formed. Therefore, it has been determined that the NiAl coating significantly enhance the isothermal oxidation resistance of the Ni0.25Co0.25Cr0.22Mo0.14Re0.14 HEA. The α-Al2O3 oxide layer has prevented severe oxidation of NiAl-coated samples due to its stability at 1050 °C over 200 h and its slow growth rate.

Effect of Isothermal Oxidation on the Structural Properties of (Ni,Pt)Al Coatings Doped with Zr at 1150 °C

The fabrication of a single-phase (Ni,Pt)Al coating, doped with zirconium, was achieved via a method that included the simultaneous electroplating of a Pt-Zr layer, followed by a process of gas-phase aluminizing. The Zr-doped (Ni,Pt)Al coating was then subjected to an evaluation of its isothermal oxidation resistance at a temperature of 1150 °C in static air compared with a conventional (Ni,Pt)Al coating. The findings indicated that the incorporation of zirconium into the (Ni,Pt)Al coating led to a marked escalation in the rate of oxidation and a worse-scale spallation resistance, which was totally opposite to the results obtained at 1100 °C. The harmful effect of Zr on the oxidation resistance of the coating is discussed in this paper.

Laser surface cladding of CoNiCrAlY as Bond Coat on INCONEL718 substrate for thermal barrier coating application

This study delves into laser surface cladding of CoNiCrAlY onto Inconel718 employing a 6.6 kW continuous wave diode laser with varying process parameters. The resulting microstructure, microhardness, and isothermal oxidation resistance are meticulously assessed. Laser surface cladding yields a defect free microstructure with the presence of gamma (γ), gamma prime (γ’) and beta (β) phases. There is negligible dilution at the interface with a minimum HAZ. The average microhardness of the clad zone ranges from 425 to 465 HV, increasing with increase in scan speed and decrease in power. The high temperature oxidation resistance property of the clad surface is superior to the same developed by high velocity oxy fuel spraying.

Investigation of microstructure and Isothermal oxidation resistance of cermet HVOF coated on AISI316L at 900 °C

The current paper examines the WCCoCr coatings using HVOF sprayed on AISI316L stainless steel and their oxidation behaviour 50 cycles at 900 °C. Oxidation kinetics was developed by calculating weight changes for uncoated and cermet sprayed samples, and the outcomes were evaluated against uncoated and coated stainless steel. Element mapping, EDS, FESEM, and XRD methods were used to examine uncoated and coated AISI316L oxidation samples. Non-protective oxide scale Fe2O3 is formed and broken due to oxidation in the uncoated sample. The scale's high Fe2O3 content caused considerable weight gain in uncoated AISI316L steel substrate. On the other hand, WCCoCr HVOF sprayed samples to have an oxide scale, and it was found that the protective Cr2O3 and WO3 phases offered notable oxidation resistance. The cermet coating reduced the weight gain of AISI316L stainless steel by 73.83%. The HVOF-sprayed AISI316L stainless steel showed superior oxidation resistance to an uncoated specimen.

The effect of Al on the oxidation behavior of Mo-6Si-12B-(1,2,4,8)Al alloys

The isothermal and cyclic oxidation behavior of Mo-6Si-12B-(1, 2, 4, 8)Al samples was investigated from 800 to 1300 ℃. With increasing Al content, the isothermal oxidation resistance is enhanced and the pesting behavior is suppressed at 800 ℃. The Mo-6Si-12B–4Al alloy with an oxide layer of both an alumino-borosilicate glasses and mullite has the best overall oxidation performance. An oxidation kinetics model was developed based upon the contributions of the individual phase oxidation rates weighted by their relative amounts and sizes that provides a good account of the oxidation behavior.

Isothermal oxidation resistance and microstructure evolution of VPS-TiAlCrY coating on TiAl single crystals at 1100–1200 °C

TiAlCrY coating was fabricated on TiAl single crystals by vacuum plasma spray (VPS) technique to investigate the oxidation resistance and microstructure evolution via isothermal oxidation tests at 1100 and 1200 ℃, respectively. The results indicated that the oxidation resistance of TiAlCrY coating was excellent with the maximum spallation degree of oxide layer extremely below the critical value of coating failure. The oxide growth kinetic curves of the TiAlCrY coating complied well with parabolic law, and the oxidation rate constants were comparable to those of typical MCrAlY coatings on nickel superalloys. In particular, the strong α-Al2O3 formation ability in the initial oxidation process and the great chemical compatibility at coating-substrate interface contributed to the durable oxidation resistance of TiAlCrY coating. This work highlights the potential application of VPS-TiAlCrY coating for TiAl single crystals at 1100–1200 ℃.

Microstructure and oxidation resistance of TiO2 modified multilayer coating prepared by HAPC/MAO

A TiO2-Nb2O5-SiO2-Al2O3/NbSi2/NbAl3 multilayer coating was prepared on Nb alloys through halide activated pack cementation (HAPC) and micro-arc oxidation (MAO). The multilayer coatings were composed of a TiO2-Nb2O5-SiO2-Al2O3 outer layer, a NbSi2 middle layer and an Al-rich inner layer. The isothermal oxidation resistance of TiO2-Nb2O5-SiO2-Al2O3/NbSi2/NbAl3 multilayer coated Nb alloy was investigated at 1100 and 1200 °C. Besides, the microstructure evolution and element diffusion of the coatings were studied at 1200 °C. The results showed that after 1200 °C oxidation for 50 h, the weight gain of TiO2-Nb2O5-SiO2-Al2O3/NbSi2/NbAl3 coating sample was 8.54 mg/cm2, which was significantly lower than the coating without TiO2. An improvement in the high-temperature oxidation resistance of coating with TiO2 should be ascribed to the formation of continuous and compact oxide scale on the surface.

High temperature oxidation performance of the electrodeposited SiO2 coating incorporated with Ni nanoparticle

Ni nanoparticle incorporated SiO2 coating was fabricated on Ti48Al2Nb2Cr alloy by electro-codeposition. Results showed that the Ni-SiO2 composite coating exhibits good isothermal and cyclic oxidation resistance at 900 ºC. The incorporation of Ni particles can adjust the coating thermal stress. After oxidation, no crack or pore can be found in the Ni-SiO2 composite coating. The consumption of the inward diffused oxygen could reduce the oxygen partial pressure at the coating/substrate interface, therefore promoting the selective oxidation of Ti48Al2Nb2Cr to form Al2O3. Owing to the good compatibility with SiO2, the oxidation product of NiO could strengthen the structure of the coating.

Effects of shot peening on microstructure, thermal performance, and failure mechanism of thermal barrier coatings

AbstractShot peening might be a potential technology to optimize the interface microstructure, plays a critical role on failure behaviors, of thermal barrier coatings (TBCs). It remains a significant challenge to understand the influence of shot peening on microstructure, oxidation resistance, and thermal shock life. In this work, the Y2O3‐stabilized ZrO2 TBCs have been deposited by EB‐PVD. The phase, microstructure, thermal performance, and failure mechanism of TBCs have been systemically investigated after shot peening. The shot peening process can improve the planeness of interface and reduce the formation of the cauliflower‐liked microstructure in TBCs. After shot peening, the TBC coatings exhibit relatively good isothermal oxidation resistance and high thermal shock life due to the optimization of TGO growth and the thermal stability. The phase transformation, TGO growth, and cracks extension might give rise to the failure of TBCs. This work might guide the investigation of the improvement of interface microstructure and failure behaviors.

Preparation and Enhanced Isothermal Oxidation Resistance of a Low Diffusivity NiRePtAl Single-Phase Coating

A low diffusivity NiRePtAl single-phase coating was formed on a Ni3Al-based SC superalloy by electroplating and aluminizing treatments, in which the electroplating consisted of depositing Ni-Re and Pt layer. The isothermal oxidation test of the sample was evaluated at 1100 and 1200 °C; the results indicated that the low diffusivity NiRePtAl single-phase sample promoted the oxidation resistance due to a greater β-NiAl phases-enriched outer layer. The Re-base diffusion barrier could effectively refrain the outward diffusion of Mo. Low diffusivity NiRePtAl single-phase coating has a lower inter-diffusion rate to the superalloy, where the thickness of the secondary reaction zone decreased by 35%. Mechanisms responsible for improved oxidation resistance and decreased extent for the formation of secondary reaction zones are discussed in the present study.

Isothermal and cyclic oxidation behavior of a sandwiched coating for C/C composites

A ZrC–SiC/TiC–SiC/SiC sandwich-structured coating is prepared on a C/C composite by pack cementation methods. The microstructures of this coating are characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the oxidation resistance is investigated by performing an oxidation test at 1773 K and a cyclic oxidation test. The results show that the mass losses are 7.4% and 3.8% after oxidation for 144 h and 40 cycles, respectively. The sandwich structure relaxes, releases the thermal stress caused by the mismatch in the coefficients of thermal expansion, and absorbs energy to prevent the initiation and propagation of cracks. The ZrC–SiC/TiC–SiC/SiC coating exhibits good isothermal oxidation resistance and excellent cyclic oxidation protection properties.

High-temperature oxidation behaviour of refurbished (Ni,Pt)Al coating on Ni-based superalloy at 1100 °C

A single-phase (Ni,Pt)Al coating was removed by soft chemical stripping method successfully after preceding oxidation at 1100 °C for 300 h, and a fresh one was refurbished subsequently. Oxidation behaviour of the refurbished (Ni,Pt)Al coating was studied in comparison with the virgin one at 1100 °C. The results show that the refurbished coating exhibited superior isothermal and cyclic oxidation resistance than the virgin one in terms of oxidation rate and surface rumpling. The effects of surface roughness and residual elements in the refurbished coating on oxidation rate, surface rumpling and interdiffusion behaviour were discussed.

The Isothermal Oxidation of MCrAlY Protective Coatings

The thermal barrier coatings (TBC) are commonly used for protection of jet engine parts. In presented article the influence of chemical composition of TBCs bond coats on isothermal oxidation resistance was analysed. The bond coat was plasma sprayed (APS) using different MCrAlY alloys produced by Oerlikon-Metco: Metco 4451, AMDRY 997, AMDRY 962, AMDRY 365-1, AMDRY 995C. The conducted research showed big difference in coating thickness despite the same spraying parameters. The difference in porosity was not observed. The isothermal oxidation test was conducted during 500h at 1100°C in static laboratory air. The obtained results showed, that degradation mechanism of MCrAlY bond coats regardless of chemical composition is similar. The formation of scale contained aluminium and chromium oxides was observed. The internal oxidation effect was also observed in produced coatings.

Characterization and oxidation behaviour of nanostructured La2(Zr0.7Ce0.3)2O7/YSZ coatings prepared by calcined precursor precipitate plasma spraying

ABSTRACTIn this study, La2(Zr0.7Ce0.3)2O7 nanostructured coatings were applied by plasma spraying of the nanostructured agglomerates. Initial nanostructured precursor, precursors calcined at 400°C, 600°C and 900°C with La2(Zr0.7Ce0.3)2O7 compound were used to apply top coat layer of the coatings. XRD results and microstructural observations indicated that a uniform distribution of LC phase in LZ matrix was obtained in the coatings applied by the precursors calcined at 400°C, 600°C and 900°C. The coatings were composed of vertical cracks. The isothermal oxidation results showed that TGO layer in the coating applied by the precursor calcined at 600°C (coating 600D60) was composed of Al2O3 protective compound. While, TGO layer in the conventional YSZ coating contained both compounds of protective Al2O3 and Ni(Cr, Al)2O4 detrimental spinel. The coating 600D60 had better isothermal oxidation resistance compared to the conventional YSZ. But, its thermal cycling resistance was approximately equal to the conventional YSZ.

(Invited) Benefits of Zr Addition on Hot Corrosion and Isothermal Oxidation Resistance of Single-Phase (Ni,Pt) Al Coatings

A Zr-doped single-phase (Ni,Pt)Al coating was prepared on a Ni-based single crystal superalloy through electroplating Pt-Zr composite layer and subsequent gaseous aluminisation treatments. Hot corrosion tests of (Ni,Pt)Al and Zr-doped (Ni,Pt)Al coatings in Na2SO4/NaCl (75:25, wt./wt.) were conducted at 850 ºC in static air. The results indicated that the Zr-doped coating showed superior hot corrosion resistance to conventional (Ni,Pt)Al coatings, in which the enhanced performance is mainly attributed to the advantageous effects of Zr that interacts with S and Cl. The mechanism and role of Zr played in the corrosion test are discussed. Moreover, isothermal and cyclic oxidation behavior of the Zr-doped (Ni,Pt)Al coating samples were assessed at 1373 K in static air compared with normal (Ni,Pt)Al coatings. The results indicated that Zr-doped (Ni,Pt)Al coating demonstrated lower oxidation rate constant and reduced tendencies of oxide scale spallation as well as surface rumpling, in which the enhanced oxidation performance was mainly attributed to the favoring effects of Zr preferring to segregate at grain boundaries of oxide scale and improving Young’s Modulus of the coating. Besides, the addition of zirconium effectively delayed the oxide phase transformation from θ-Al2O3 to α-Al2O3 in early oxidation stage and the coating degradation from β-NiAl to γ'-Ni3Al in stable oxidation stage.

(Invited) Benefits of Zr Addition on Hot Corrosion and Isothermal Oxidation Resistance of Single-Phase (Ni,Pt) Al Coatings

A Zr-doped single-phase (Ni,Pt) Al coating was prepared on a Ni-based single crystal superalloy through electroplating Pt-Zr composite layer and subsequent gaseous aluminisation treatments. Hot corrosion and isothermal oxidation tests of NiAl, (Ni,Pt) Al and Zr-doped (Ni,Pt) Al coatings were conducted in static air. The results indicated that Zr-doped coatings showed superior hot corrosion resistance to both conventional aluminide and (Ni,Pt) Al coatings, the enhanced performance was mainly attributed to the advantageous effects of Zr that interacted with S and Cl. The mechanism and role of Zr played in the corrosion test are discussed. Meanwhile, Zr-doped (Ni,Pt) Al coating demonstrated lower oxidation rate constant, which was mainly attributed to the favoring effects of Zr preferring to segregate at grain boundaries of oxide scale. Besides, the addition of zirconium effectively delayed the oxide phase transformation from θ-Al2O3 to α-Al2O3 in early oxidation stage and the coating degradation from β-NiAl to γ'-Ni3Al in stable oxidation stage.

The role of Re in effecting isothermal oxidation behavior of β-(Ni,Pt)Al coating on a Ni-based single crystal superalloy

Two β-(Ni,Pt)Al coatings with or without Re doping and a PtAl diffusion coating were prepared on a single crystal Ni-based superalloy. Isothermal oxidation behavior of all the coatings was investigated at 1100 ℃ for 300 h. The Re doped β-(Ni,Pt)Al coating possessed the best isothermal oxidation resistance because Re reduced the oxidation rate and extent of β to γ′ phase degeneration. The oxidation mechanism of the PtAl diffusion coating and advantageous roles of Re on the effect of the morphologies, anti-spallation and rumpling behavior of thermally grown oxide (TGO) were discussed as well.

Improvement of isothermal oxidation resistance of a γ′-strengthened Co–Al–W–Mo–Ta–B alloy at 800 °C via doping Ce

Isothermal oxidation resistance, oxide scale evolution and failure mechanism of Ce-doped Co–Al–W–Mo–Ta–B alloy (0.01 at%, 0.05 at%, 0.10 at% and 0.20 at% Ce) exposed at 800 °C were compared. The 0.01Ce and 0.05Ce alloys were consisted of γ/γ′ coherent microstructure, while the κ-Co3W compound precipitated at the grain boundary of the 0.10Ce and 0.20Ce alloys in addition to the γ/γ′ microstructure. The oxidation kinetics curves of the Ce-doped alloys exhibited a parabolic time dependence on the weight gain. With an increasing nominal Ce content, the weight gain of the Co–Al–W–Mo–Ta–B alloys monotonically decreased. An oxide scale composed of a dense and uniform outer Co3O4 + CoO layer, a middle CoAl2O4 and CoWO4 compound layer and an inner Al2O3 layer. The excellent oxidation resistance of 0.2Ce alloy was mainly attributed to a shorter incubation stage for the formation of the continuous and protective Al2O3 layer and the thickest Al2O3 layer during entire oxidation process.

Correlation Between Microstructure and High-Temperature Oxidation Resistance of Jet-Electrodeposited Ni-Based Alloy Coatings

In the present study, Ni-based alloy coatings were prepared on copper substrates by jet electrodeposition, and their oxidation resistance was evaluated by isothermal oxidation resistance tests at 700, 800, and 900 °C, respectively. The oxidation kinetics of the jet-electrodeposited alloy coatings follow the parabolic rate law. The oxidation resistance of Ni and NiFe coatings is superior to that of jet-electrodeposited NiW coating, while the deposited ternary NiFeW alloy coatings exhibited the highest oxidation resistance. The enhanced high-temperature oxidation resistance could be mainly attributed to the excellent thermal stability of Fe2O3 and NiO phases formed in the alloy coatings during oxidation.

Comparative Isothermal Oxidation Resistance of Selected Single-Crystal Ni-Based Superalloys With and Without Pt-Modified Surface Layers

Isothermal oxidation tests at 1150 °C show that the commercial grade of the single-crystal Ni-based superalloy CMSX-4 is superior to that of the CMSX-10 version. Superalloy CMSX-4 is observed to undergo a shorter stage of transient oxidation and to be able to form more protective oxides during the earlier stages of the reaction as compared to superalloy CMSX-10. This behavior is correlated with the difference in chemical composition between the two superalloys. A significant improvement in oxidation resistance of both superalloys is realized after diffusing a 10 μm thick layer of Pt into their surfaces to produce a Pt-rich surface layer of γ′-phase. However, the oxidation resistance of the composite Pt/CMSX-10 system becomes superior to that of the Pt/CMSX-4 system. Most evidence indicates that this is a reflection of the higher microstructural stability of the γ′-phase in superalloy CMSX-10 and the added beneficial effect provided by Pt.