High Temperature Cyclic Oxidation Behavior Research Articles

High-Temperature Cyclic Oxidation Behavior and Microstructure Evolution of W- and Ce-Containing 18Cr-Mo Type Ferritic Stainless Steel.

Due to the recurrent starting and stopping operations of automobiles during service, their engines' hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion.

High temperature oxidation behavior of thermal and plasma processed aluminide coated Ti6Al4V alloys

In this study, the high temperature cyclic oxidation behavior of thermal and plasma-treated aluminide coated Ti6Al4V alloy was investigated at 800 °C up to 360 h in 24 h cyclic exposures. The microstructural characteristics, phase analysis, morphological features, and microhardness of resultant oxidized samples were evaluated and compared with those of untreated Ti6Al4V alloy. The weight gain studies conducted from the cyclic oxidation tests revealed very minimal weight gain in plasma treated (PT) aluminide coated samples as compared to the thermal treated (TT) and uncoated (UC) samples. XRD results indicate that the UC samples oxidized at 800 °C exhibits the formation of a thick oxide layer consisting of only the rutile phase (TiO2). The TT and PT samples oxidized at 800 °C revealed presence of both alumina (Al2O3) and rutile (TiO2) phases. However, PT samples revealed stable α-Al2O3 phase whereas the TT samples showed metastable θ-Al2O3 phases in the oxide layer. The surface morphological features reveal that the oxide film formed on the surface of the PT samples had enough stability at 800 °C irrespective of the oxidation time. The PT samples exhibited higher hardness and improved oxidation resistance as compared to TT and UC samples. Increase in thermal stability, mechanical and oxidation properties of PT samples could be attributed to the formation of stable alumina (α-Al2O3) and presence of nanocrystalline aluminide phases (TiAl3 & TiAl2) in the diffusion layers during the oxidation tests. Therefore, a strong emphasis was placed on correlating the interfacial processes to the high temperature oxidation behavior.

High temperature oxidation resistance of an amorphous layer induced by ion implantation on the surface of Ni-based superalloy GH202

The high-temperature cyclic oxidation behavior of Ni-based superalloy GH202 was investigated before and after Y ion implantation at 1100 °C. The chemical composition and microstructure of the alloy surface treated by ion implantation were characterized using X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, electron probe microanalysis, and scanning electron microscopy. The results showed that a 30-nm-thick amorphous layer formed on the surface of the superalloy. The collision of Y ions with the alloy atoms resulted in a large number of crystal defects, such as vacancies and dislocations. Upon increasing the implantation dose, the shock of the ions prompted the dislocations to move and form dislocation tangles and dislocation arrays, which provided short circuit diffusion channels for aluminum (Al) ions during high-temperature oxidation. The oxide film on the surface of the specimens treated by ion implantation remained intact after 40 oxidation cycles, and no internal oxidation occurred in the substrate. The Y ions provided heterogeneous nucleation particles, reduced the distance between the Al2O3 nucleation positions, and promoted the formation of continuous, dense films. The amorphous layer changed the oxidation mechanism from outward cation diffusion in the oxide films to inward anion diffusion. The growth rate of the oxide film was effectively inhabited, and the high-temperature oxidation resistance was significantly improved.

The effect of alloying elements on oxide scale spallation of multicomponent Co-based superalloys

The characterization of high temperature cyclic oxidation behavior of as-cast and as-aged Co-(Ni)-Al-W alloys, and the influence of alloying elements on oxide spallation resistance have been investigated in this study. The cyclic oxidation and oxide scale morphology of the alloys are analyzed from 700° to 900°C. It has been observed that the ternary Co-Al-W alloys are prone of oxide scale spallation and increasing the Al, W and Ni contents improves the cyclic oxidation resistance of the alloys. The structural effect of Ni on oxidation performance is related to its introduction to single and complex oxides present in a scale.

High-temperature cyclic oxidation behavior and mechanism of Mo2FeB2-based cermets with various boron contents

In this study, cyclic oxidation behavior and mechanism of Mo2FeB2-based cermets have been investigated by varying the boron content. The parabolic curves of mass gain confirmed the formation of the protective oxide layer. Mo2FeB2-based cermets with boron content of 6 wt.% had the lowest mass gain due to the denser and continuous oxide layer. A typical multi-layer structure could be observed in the cross-section, which was mainly composed of Fe oxide, borate and molybdate. The borate layer could effectively inhibit the diffusion of oxygen to protect the matrix from rapid oxidation. Furthermore, higher boron content could facilitate the oxide layer to be denser, which is beneficial to the oxidation resistance. However, the “pesting oxidation” would appear after 50 h oxidation at 800 °C, which causes the curves of mass gain to transform from parabolic to linear trend.

High temperature cyclic oxidation behavior of a low manganese Fe12Mn9Cr5Si4Ni-NbC shape memory stainless steels

High amounts of Mn in Fe-Mn-Si-Cr-Ni shape memory stainless steels are detrimental for oxidation resistance at high temperatures. However, in order to maintain the shape memory effect of these alloys the content of manganese must be between 12 and 19 wt%. Thus, this study evaluated an alloy with relative low Mn (12 wt%) in cyclic oxidation tests at 800, 900 and 1000 °C. Kinetic analysis demonstrated parabolic oxidation behavior with rate similar to higher Mn-containing alloys from literature. It was also observed internal oxidation, for the first time in these alloys, and oxide layers composed by Mn2O3 and Mn-Cr spinel at 800 °C as well as Mn-Cr spinel and no continuous silica at 1000 °C. The internal oxidation mechanism was related to oxide layer defects and not to partial oxygen pressure decrease, considering that the internal oxidation presented the same oxides of the external layer. These results show that low Mn content does not improve the use viability of these alloys at high temperatures, since no decreasing in oxidation rate was observed and further internal oxidation occurred.

Investigation on the effect of Si addition to the high temperature cyclic oxidation behaviour of β-NiAlDy alloy used in advanced jet engine applications

Abstract This work concentrates on the study of the effect of addition of Si to the β-NiAlDy alloy in improving its cyclic oxidation behaviour at high temperature namely 1000 0C. Silicon addition of 1%, 3% and 5% are carried out to prepare β-NiAlDy alloy groups by arc-melting and further by casting in inert atmosphere. The prepared alloy groups were further subjected to annealing in vacuum at temperature namely 1100 0C for a time period of 12 h. These alloy groups are subjected to cyclic oxidation tests up to 100 cycles with each cycle time duration of 5 h of atmospheric exposure at aforementioned temperature. The oxidation behaviour of the alloy groups were studied in detail by carrying out cyclic oxidation measurements, XRD, SEM and EDAX analysis. The results clearly show the variation of oxidation behaviour of the β- NiAlDy alloy when Si content is increasing from 1 to 5%. It is registered that the oxidation resistance of β-NiAlDy increase to a greater extent when 1 to 5% Si is added to the alloy.

Thermal Cyclic Behaviour of Conventional YSZ and Mullite-YSZ Thermal Barrier Coatings

Nowadays commonly used thermal barrier coatings (TBC) are based on yttria stabilized zirconia (YSZ). Addition of mullite phase into the YSZ coating can improve resulting high temperature properties. The contribution focuses on high temperature cyclic oxidation behaviour of two TBC systems with different top coats (TC) deposited by the means of atmospheric plasma spraying. The initial mullite-YSZ powder mixture consisted of 29 vol. % of mullite and 71 vol. % of YSZ. The conventional TBC system consisted of ~ 150 µm thick NiCoCrAlYHfSi bond coat (BC) and ~ 300 µm thick YSZ top coat. The experimental mullite-YSZ (MYSZ) TBC system consisted of ~ 150 µm thick NiCoCrAlYHfSi bond coat, ~ 100 µm thick YSZ interlayer and ~ 200 µm thick mullite-YSZ top coat. The experimental TBC proved higher lifetime, durability and phase stability and also lower grow rate of thermally grown oxide (TGO) compared to conventional TBC. Lifetime, phase stability and changes in the microstructure of TBCs after the furnace cyclic oxidation test were evaluated by the means of scanning electron microscopy equipped with EDX analyzer and X-ray diffraction techniques. Oxidation kinetics of TGO was calculated based on thickness determined utilizing digital image analysis.

High Temperature Cyclic Oxidation Behaviour Ternary Ni-Al-Ti Alloys doped with Ge at 1200oC

Ni base alloys are widely used for high temperature applications, such as pressure vessel , turbine blade. Ni-base alloys possess oxidation resistance, creep resistance, fatigue resistance, the stability of the microstructure and good mechanical properties at elevated temperatures. The Ni-Al-Ti alloys were melted in a single arc melting furnace under ultra high argon atmosphere. Cyclic oxidation of the alloys was performed in air furnace at 1200 °C temperature for 25 cycles Each cycle consisted of 1 hr heating at 1200°C in an alumina tube furnace followed by 30 min cooling at room temperature. The results show that the higher addition of Ge element content can improve the mechanical properties and oxidation resistance of Ni based alloys. X-ray diffraction examination showed that the compounds were formed on the alloy after smelting Ni 3 Al, Ni 3 Ti, Ni 3 Ge, Ni and Ni 2 AlTi. While the oxide on the alloy after oxidizing to form a compounds NiO, NiTiO 3 , GeO 2, and TiO 2 . In the SEM-EDS examination showed that the composition of Ge formed more dominant in the area under the element Ni oxide layer. The higher the Ge element content in the alloy has improved the resistance of the alloy indicated by the thin layer of oxide formed on the surface of the alloy.

High Temperature Oxidation Behavior of Boron Carbide

The aim of this study is to determine the high temperature cyclic oxidation behavior of boron carbide (B 4 C) in air atmosphere at elevated temperatures. For this purpose, as-received powders were firstly characterized by XRD and SEM. Boron carbide powders were shaped by cold pressing for oxidation studies. Tests were performed in air atmosphere at 800˚C and 1000˚C for 5, 10, 15 and 20 hours. After each oxidation test, the mass changes were measured. XRD, SEM and EDS analyses were conducted on the oxidized samples and the results were discussed. It was observed that cyclic oxidation behaviors of the samples depended on temperature and time. Based on the analyses results and the microstructure observations, volatilization of B 2 O 3 had significant effect on the oxidation of the samples as the temperature increased.

Microstructural homogenization and high-temperature cyclic oxidation behavior of a Ni-based superalloy with high-Cr content

A new Ni-based superalloy with high-Cr content was designed for industrial gas turbines application. The microstructural homogenization and high-temperature cyclic oxidation behavior was investigated systematically. The results showed that the optimum heat treatment condition was 1563 K (1290 °C)/4 h + 1573 K (1300 °C)/6 h, A.C. (air cooling) + 1393 K (1120 °C)/2 h, A.C. + 1143 K (870 °C)/24 h, A.C., which can completely dissolve the γ/γ′ eutectic and the Ni3(TiTa) phase in the interdendritic region. The cyclic oxidation results showed that a multilayer of continuous and dense oxide-rich regions formed and the kinetic curves followed a parabolic law. The mass gain at 1323 K (1050 °C) and 1343 K (1070 °C) was 4.02 mg/cm2 and 4.23 mg/cm2, respectively. No severe spallation of the oxide-rich region was observed. The outer layer of the oxide-rich region mainly consisted of Cr2O3, TiO2, and (Ni, Co)Cr2O4 spinels, while the layer at the substrate-oxide interface was found to be Al2O3. The results show that this new superalloy has a better cyclic oxidation resistance at 1343 K (1070 °C) than the commonly used IN738 and GTD-111 superalloys.

High temperature cyclic oxidation of Ni based superalloys at different temperatures in air

In present study high temperature cyclic oxidation behavior of Ni-based superalloy (Inconel 617) was investigated. The cyclic oxidation test was carried out at various temperatures 750 °C, 850 °C, 950 °C and 1000 °C under cyclic conditions in the air for 96 h. Weight gain is measured discontinuously at different oxidation temperatures and times. Weight gain was used to determine the kinetics of oxidation. The oxidation kinetics of the alloys followed a parabolic rate law at 850 °C, 950 °C and 1000 °C. Field emission scanning electron microscopy/energy dispersive spectroscopic analysis (FESEM/EDAX) technique was used to analyze the oxidation products. X-Ray Diffraction (XRD) was used to analyze the formed scale. The protective oxides of Cr2O3, NiO, and NiCr2O4 were formed, which contributed to the better oxidation resistance. These oxide scales increased with time and temperature and they are compact, dense, distributed uniformly and adherent to the surface of Inconel 617 alloy.

High temperature cyclic oxidation behavior of ferritic stainless steel with addition of alloying elements Nb and Ti for use in SOFCs interconnect

In the present work, high-temperature cyclic oxidation of ferritic stainless steel (FSS) with minor addition of Nb and Ti elements has been carried out at 800 °C in air for 70 cycles. Thermal cycling consists of 1 h heating in furnace followed by 15 min cooling to room temperature outside the furnace. The weights of all the specimens were measured every 1 cycle. The specimens were examined by scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). The purpose of making this alloy was for application in solid oxide fuel cells (SOFCs) interconnects. The addition of minor alloying elements, especially Nb, led to formation of Laves phases in oxide/metal interface and prevented the diffusion of cation to the oxide scale. It is also a barrier for the influence of the oxygen anion to the inward of the FSS. The presence of high amount of Nb and low amount of Ti were effective on improving of the oxidation. By increasing amount of Ti compare to Nb in this steel caused the increased oxidation rate.

High-temperature cyclic oxidation behavior of Al2O3–YAG composite coating prepared by EPD and microwave sintering

Al2O3–YAG (Y3Al5O12) composite coatings were successfully fabricated on NiCoCrAlY alloy substrates by electrophoretic deposition (EPD) in Y3+ doped composite sol–gel suspensions and pressure filtration microwave sintering (PFMS). The composite coating was dense, crack-free and had good adherence with substrate even after cycling oxidation at 1000°C for 200h. Filed emission SEM showed that nano-size YAG particles were embedded in α-Al2O3 matrix. The high-temperature cyclic oxidation tests revealed that the oxidation resistance and spallation resistance were greatly improved. The oxidation resistance of alloy is mainly determined by α-Al2O3 sealing effect and reactive elements effects (REE) on the thermally grown oxide (TGO) scale. Moreover, the enhanced fracture toughness and strength of this composite coating can be attributed to the nano/submicro composite structure and YAG particles toughening effects.

High Temperature Cyclic Oxidation Behavior of Ni and Co Based Superalloys

High temperature oxidation causes degradation of materials in aircraft, marine, industrial and land base gas turbines. To obviate this problem, oxidation behavior of Ni and Co based superalloys viz superni 600 and superco 605 (Midhani grade) has been studied in air at 900oC. Both superalloys go through cyclic oxidation which consists of 1 hr heating in silicon carbide tube furnace followed by 20 min cooling in ambient air. Weight change was taken by a digital electronic weighing balance having accuracy of 1 mg after each cycle. Exposed alloys were characterized by XRD, FESEM and EDS. Result shows that the Co base superalloy superco 605 shows less weight gain as compare to superni 600. The oxide layer mainly contains oxides of Cr2O3, NiO and spinel NiCr2O4.

Evolution of Al<sub>2</sub>O<sub>3</sub> Scale Formed on Ni-Al-Pt Alloy in Atmospheres Containing Water Vapor

High temperature cyclic oxidation behavior of γ'-base Ni-25Al-10Pt (in at.%) alloy was investigated at 1000°C in air with and without 30vol.%H2O. The oxidation mass gain during the initial stage of oxidation was similar in both atmospheres, but the oxidation rate in air+H2O was lower in the longer steady-state oxidation stage. Metastable Al2O3, which formed during the initial stage of oxidation, transformed completely after about 100hr of oxidation in dry air. The transformation to α-Al2O3also occurred in air+H2O, but complete transformation to α-Al2O3was not observed during the oxidation time in the present study. θ-Al2O3grains remained for longer on the α-Al2O3layer in air+H2O and became significantly coarser with oxidation time. The present results indicate that water vapor delays the metastable to α-Al2O3phase transformation, and decreases the growth rate of α-Al2O3.

High temperature cyclic oxidation behavior of Y2O3-ZrO2 thermal barrier coatings irradiated by high-intensity pulsed ion beam

The high-temperature oxidation resistance behavior of 7% (mass fraction) Y2O3-ZrO2 thermal barrier coatings (TBCs) irradiated by high-intensity pulsed ion beam (HIPIB) was investigated under the cyclic oxidation condition of 1 050 °C and 1 h. The columnar grains in the TBCs disappear after the HIPIB irradiation at ion current densities of 100–200 A/cm2 and the irradiated surface becomes smooth and densified after remelting and ablation due to the HIPIB irradiation. The thermally grown oxide (TGO) layer thickness of the irradiated TBCs is smaller than that of the original TBCs. After 15 cycles, the mass gains of the original TBCs and those irradiated by ion current densities of 100 and 200 A/cm2 due to the oxidation are found to be 0.8–0.9, 0.6–0.7, and 0.3–0.4 mg/cm2, respectively. The inward diffusion of oxygen through the irradiated TBCs is significantly impeded by the densified top layer formed due to irradiation, which is the main reason for the improved overall oxidation resistance of the irradiated TBCs.

High temperature cyclic oxidation behavior of magnetron sputtered Ni–Al thin films on Ni- and Fe-based superalloys

Ni–Al thin films were deposited on Ni- and Fe-based superalloys by RF magnetron sputtering in this work. The microstructures of the as-deposited films were characterized by XRD, AFM, and FE-SEM/EDS. The grain size of the Ni–Al thin films, using XRD results, was found to be 8.1 nm, 9.22 nm and 16.04 nm for Superni 76 (SN 76), Superni 750 (SN 750) and Superfer 800 (SF 800), respectively. The surface roughness of NiAl coated superalloys was calculated by using its AFM images and it showed a regular smooth surface. The Ni–Al thin films deposited superalloys were subjected to oxidation studies at 900 °C for 100 cycles. The kinetics of oxidation was determined from the weight change of the samples monitored under cyclic conditions. The oxide scales formed on the bare and Ni–Al deposited superalloys were characterized to elucidate the mechanisms of high temperature oxidation. The SF 800 superalloy has provided a better oxidation resistance in the given environment compared to SN 76 and SN 750 alloy. The weight gain was high in case of Ni–Al coated SN 750 but it was less on the coated SF 800 alloy, indicating a better protection among the coated superalloys.

Influence of silicon on high-temperature cyclic oxidation behaviour of titanium

The paper compares the high-temperature cyclic oxidation behaviour of TiSi2 and TiSi8 with that of pure titanium. One experimental cycle consisted of heating at a temperature of 850 °C or 1050 °C for 12 h, followed by rapid cooling to the room temperature. Each experiment comprised six cycles. The cyclic oxidation kinetics as well as the structure, properties and composition of scales were investigated. The experiments clearly proved the positive effect of silicon on the cyclic oxidation resistance of titanium. The influence of silicon was shown to be more pronounced at a lower temperature of the cyclic oxidation (850 °C). At a higher oxidation temperature (1050 °C), its influence was still evident but less significant. In contrast to the Ti–Si alloys oxidised at 850 °C, the scales formed after cyclic oxidation at 1050 °C were much more porous and cracked due to stresses induced upon rapid cooling. A higher fraction of coarse silicide particles in the case of the TiSi8 alloy resulted in an increased cracking and porosity of the scales. The structure of the scales formed after oxidation at 1050 °C was complex. The scales were composed of at least two sub-layers, one containing a negligible concentration of silicon and the other, inner one, containing an increased amount of silicon. The nitride layer occurring beneath the scales was thicker for the TiSi8 alloy, due to a higher fraction of the scale porosity.

The use of thin layer activation in high-temperature cyclic oxidation studies

Thin layer activation (TLA) has been applied to a study of the high-temperature cyclic oxidation behaviour of pure and yttrium-implanted chromium, taking advantage of the high area selectivity of the technique. On pure chromium, two different sample areas, i.e. corners and the central part of a large surface area, were selected for activation. Due to this area selectivity, it was possible to distinguish the spallation behaviour of the oxide scale formed on flat from that formed on highly curved surfaces. In particular, the TLA data showed that the oxide scale formed during high-temperature cyclic oxidation near corners and edges was more prone to cracking and spallation. In the case of yttrium-implanted specimens, activation was performed only at the centre of the implanted zone, avoiding the distorting effect of the non-implanted parts of the sample. The area selectivity of TLA made it possible to study more accurately the beneficial effect of ion implantation on the cyclic oxidation behaviour than by conventional thermogravimetry. Due to the complementary character of TLA with respect to the conventional thermogravimetry, a more complete and better understanding of the cyclic oxidation performance of materials can be obtained.