Effect of Mo on the Oxidation Behavior of NiTiAl Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 1481-1484
Author(s):  
Jian Xu ◽  
Xin Qing Zhao ◽  
Sheng Kai Gong
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Oxide Layer ◽  
Oxygen Diffusion ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Oxide Scales ◽  
Cross Sectional ◽  
Oxidation Layer ◽  
Poor Adhesion

The effect of Mo on the oxidation behavior of TiNiAl at 1073K has been investigated. It is found that 1at.% Mo addition can increase the diffusion of Al in the alloys and promote the formation of dense and continuous Al-rich oxide layer. Therefore the oxygen diffusion can be effectively impeded and the oxidation behavior of TiNiAl is improved. The observation of the cross-sectional oxidation layer showed that beneath the top oxide scale a Mo-rich oxide layer formed. Because the oxide of Mo is volatile at high temperature, voids formed in the oxide scales during the oxidation process. 3at.% Mo addition could cause cracks between the oxide scale and the substrate, resulting in poor adhesion of the oxide scale to the substrate.

scholarly journals Exploring the Effect of Silicon on the High Temperature Corrosion of Lean FeCrAl Alloys in Humid Air

2021 ◽  
Author(s):  
T. Sand ◽  
A. Edgren ◽  
C. Geers ◽  
V. Asokan ◽  
J. Eklund ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Oxidation Behavior ◽  
High Temperature Corrosion ◽  
The Other ◽  
Oxide Scales ◽  
Protective Oxide ◽  
New Approach ◽  
Fecral Alloys ◽  
Cr Evaporation

AbstractA new approach to reduce the chromium and aluminium concentrations in FeCrAl alloys without significantly impairing corrosion resistance is to alloy with 1–2 wt.% silicon. This paper investigates the “silicon effect” on oxidation by comparing the oxidation behavior and scale microstructure of two FeCrAl alloys, one alloyed with silicon and the other not, in dry and wet air at 600 °C and 800 °C. Both alloys formed thin protective oxide scales and the Cr-evaporation rates were small. In wet air at 800 °C the Si-alloyed FeCrAl formed an oxide scale containing mullite and tridymite together with α- and γ-alumina. It is suggested that the reported improvement of the corrosion resistance of Al- and Cr-lean FeCrAl’s by silicon alloying is caused by the appearance of Si-rich phases in the scale.

Oxidation Behavior of Amorphous Nano-Si3N4 Powders

2014 ◽  
Vol 602-603 ◽  
pp. 367-370 ◽  
Author(s):  
Jiang Bo Wen ◽  
Sheng Huang ◽  
Hong Jie Wang
Keyword(s):  
High Temperature ◽  
Partial Pressure ◽  
Mechanical Behavior ◽  
Low Temperatures ◽  
Traditional Method ◽  
Oxidation Behavior ◽  
Oxidation Process ◽  
Composite Ceramic ◽  
Intergranular Phase ◽  
Sintering Additives

The traditional method preparing Si3N4/Si2N2O composite ceramic is to sinter α-Si3N4 powder with additives at relatively high temperatures. But the intergranular phase transformed from the sintering additives can degrade the high-temperature mechanical behavior. Amorphous nanoSi3N4 is used to fabricate Si3N4/Si2N2O composite ceramic by its oxidation and nitridation without sintering additives at low temperatures. Thus, it is essential to study the oxidation behavior and mechanism of amorphous nanoSi3N4. Amorphous nanoSi3N4 powders were oxidized in different atmospheres, at varying temperatures and for various different length of time. The oxidation process and products was analyzed by means of XRD, TGA and FTIR. The results showed that amorphous nanoSi3N4 could be oxidized into SiO2 from 600°C to 1300°C. Below 1300°C, the oxidation became serious as the temperature increased. Besides, the longer the oxidation time and the lager the ratio of O2/N2 partial pressure was, the deeper the oxidation level was. When the temperature was above 1300°C, amorphous nanoSi3N4 was completely oxidized into SiO2.

Oxidation Behavior of Mo Containing Alloys

2008 ◽  
Vol 595-598 ◽  
pp. 959-966 ◽  
Author(s):  
Esra Dokumacı ◽  
Bulent Önay
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Oxidation Behavior ◽  
Melting Furnace ◽  
Oxidation Products ◽  
Protective Oxide ◽  
High Temperature Furnace ◽  
Negative Effect ◽  
Backscattered Electron ◽  
Protective Environment

In this study, high temperature (T>500oC) oxidation behavior of two commercial Ni-base alloys and two experimental alloys, all containing more than 10% Molybdenum, is investigated. Experimental alloys were prepared from high purity materials using an arc-melting furnace under a protective environment. During tests, samples were exposed to the stagnant air environment of a high temperature furnace for predetermined times. Extent of oxidation was determined from sample mass change measurements as well as morphological and chemical analyses of the oxidation products. For analyses, a scanning electron microscope (SEM) equipped with backscattered electron (BE) and energy dispersive spectroscopic (EDS) detectors was used. Crystalline phases formed in the product scales over the alloy samples were identified by an x-ray diffractometer (XRD). Preliminary results indicate that although Mo in the alloy prevents the development of a protective oxide scale at the alloy surface, presence of alloying elements such as Cr or Al can decrease this negative effect of Mo on oxide scale formation.

scholarly journals Investigation on Oxidation Behavior of Super304H and HR3C Steel in High Temperature Steam from a 1000 MW Ultra-Supercritical Coal-Fired Boiler

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 521
Author(s):  
Jingjing Li ◽  
Haidong Ma ◽  
Yungang Wang ◽  
Min Xue ◽  
Qinxin Zhao
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Outer Layer ◽  
Oxidation Product ◽  
Oxidation Behavior ◽  
Product Layer ◽  
Two Samples ◽  
High Temperature Steam

Oxidation behavior of Super304H and HR3C steel in high temperature steam from an ultra-supercritical coal-fired boiler was investigated in this paper. The results showed that the steam oxidized surface of Super304H ware composed of Fe2O3, Cr2O3 and FeCr2O4, the oxide scale had a thickness of 50–70 μm. In addition, the steam oxidized surface of HR3C ware composed of Fe2O3, the oxide scale was about 20μm in thickness and contained few pitting. The oxidation product layer of the two samples could be divided into two layers, including outer layer enriched O element and Fe element, and inner layer enriched O element and Cr element. Furthermore, oxide scale spalling was observed on the surface of Super304H sample.

Isothermal Oxidation Behavior of Ni Base Superalloy DM02 for High Temperature Dies

2007 ◽  
Vol 546-549 ◽  
pp. 1253-1256
Author(s):  
Qing Li ◽  
Jin Xia Song ◽  
Cheng Bo Xiao ◽  
Shi Yu Qu ◽  
Ding Gang Wang ◽  
...  
Keyword(s):  
Weight Gain ◽  
High Temperature ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Growth Mechanism ◽  
Oxidation Kinetics ◽  
Oxidation Behavior ◽  
Isothermal Oxidation ◽  
Good Oxidation Resistance ◽  
Base Superalloy

The isothermal oxidation behavior of a new developed Ni base superalloy named DM02 for high temperature dies was studied in this paper. The dynamic curve was achieved by monitoring weight gain of the alloy as a function of time. The results showed that the alloy had fairly good oxidation resistance at 1050°C and 1100°C. The oxidation kinetics at both 1050°C and 1100°C followed parabolic rules in segment. It has been found that the oxidation of the alloy was controlled by multi-oxides of (Ni, Co)O, (Ni, Co)Al2O4, and NiWO4, growth mechanism in the primary stage, and by Al2O3, NiAl2O4 growth mechanism in the following stage. After oxidation at 1050°C for 100h, the oxide scale of the alloy was mainly composed of two areas. Some were thin uniform (Ni， Co)Al2O4(outer)/Al2O3 (inner) composites scale and others were multi-layer oxide scale of ( Ni,Co)O / multi-oxides (mainly NiWO4、NiO and NiAl2O4.) /Al2O3.

Study on Laser-Induced Oxidation of Ti6Al4V Alloy Under Two Different Reactive Atmospheres

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Wei Zhao ◽  
Guolong Zhao ◽  
Ning He ◽  
Liang Li ◽  
Asif Iqbal
Keyword(s):  
Laser Irradiation ◽  
Oxide Layer ◽  
Laser Fluence ◽  
Oxidation Behavior ◽  
Phase Identification ◽  
Oxidation Reactions ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Subsurface Layers

Abstract The oxidation behavior of Ti6Al4V titanium alloy under laser irradiation in atmospheric and oxygen-assisted conditions was studied. A nanosecond-pulsed Yb: glass fiber laser was used. The thickness of oxide layer, microstructure, and phase composition of the material after laser irradiation were investigated. The characterization of the surface and subsurface microstructure, as well as the cross-sectional morphology were performed using scanning electron microscopy (SEM). The phase identification was performed using X-ray diffraction (XRD). The combined effects of accumulated laser fluence and reactive atmosphere on the oxidation behavior of Ti6Al4V were also studied in detail. With an increase in accumulated laser fluence, a porous and easily removable oxide layer gradually formed on the surface, whereas a compact oxide layer was also formed. At high accumulated laser fluence, the thickness of the porous oxide layer increased dramatically, while the change of thickness of compact oxide layer was not obvious. The reactive atmosphere also had a significant influence on the microstructure of the surface and subsurface layers. SEM and XRD results revealed existence of strong oxidation reactions that underwent in the condition of assisted oxygen delivery at a fixed accumulated laser fluence. The oxide layer was composed mainly of anatase and rutile titanium oxides.

scholarly journals High Temperature Oxidation Behavior of Selective Laser Melting Manufactured IN 625

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 668 ◽  
Author(s):  
Mihaela Raluca Condruz ◽  
Gheorghe Matache ◽  
Alexandru Paraschiv ◽  
Teodor Badea ◽  
Viorel Badilita
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Selective Laser Melting ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Complex Oxide ◽  
Mass Gain ◽  
Laser Melting ◽  
Temperature Oxidation ◽  
High Temperature Oxidation Behavior

The high-temperature oxidation behavior of selective laser melting (SLM) manufactured IN 625 was studied over 96 h of exposure at 900 °C and 1050 °C in air. An extensive analysis was performed to characterize the oxide scale formed and its evolution during the 96 h, including mass gain analysis, EDS, XRD, and morphological analysis of the oxide scale. The mass gain rate of the bare material increases rapidly during the first 8 h of temperature holding and diminishes at higher holding periods for both oxidation temperatures. High-temperature exposure for short periods (24 h) follows a parabolic law and promotes the precipitation of δ phase, Ni-rich intermetallics, and carbides. Within the first 24 h of exposure at 900 °C, a Cr2O3 and a (Ni, Fe)Cr2O4 spinel scale were formed, while at a higher temperature, a more complex oxide was registered, consisting of (Ni, Fe)Cr2O4, Cr2O3, and rutile-type oxides. Prolonged exposure of IN 625 at 900 °C induces the preservation of the Cr2O3 scale and the dissolution of carbides. Other phases and intermetallics, such as γ, δ phases, and MoNi4 are still present. The exposure for 96 h at 1050 °C led to the dissolution of all intermetallics, while the same complex oxide scale was formed.

Effects of Si Content on the Oxidation Behavior of Fe–Si Alloys in Air

2011 ◽  
Vol 696 ◽  
pp. 126-131 ◽  
Author(s):  
Takumi Nishimoto ◽  
Kazuhiko Honda ◽  
Yasumitsu Kondo ◽  
Kenichi Uemura
Keyword(s):  
Oxide Scale ◽  
Cross Sections ◽  
Oxidation Kinetics ◽  
Oxidation Behavior ◽  
Elemental Distribution ◽  
Oxide Scales ◽  
Scale Thickness ◽  
Internal Oxidation Zone ◽  
Diffusion Controlled ◽  
Si Content

The oxidation behavior of Fe–Si alloys at 1073K in air was investigated. The oxidation kinetics described by the parabolic rate law of diffusion controlled oxidation and the oxidation rate decrease with the increasing Si content. Fe-Si alloys were oxidized for different times at 1073K to obtain the same scale thickness of approximately 30μm. Observations of scale cross-sections indicated the structure of oxide scale and elemental distribution in oxide scales strongly depends on Si content. The oxide scale on Fe-Si alloys with low Si content consisted of three layers with an outer Fe2O3, an intermediate Fe3O4 and an inner FeO and some voids were formed in Fe3O4 and FeO layers. The Si-rich oxide layer was formed at the scale/alloy interface of Fe-Si alloys with high Si content. Furthermore, the amount of internal oxidation zone increased with the increasing Si content. Observations of scale cross-sections indicated that the structure of oxide scale and elemental distribution in oxide scale strongly depend on Si content.

Microstructure and Phase Identification of Tertiary Oxide Scale on Steel by EBSD

2009 ◽  
Vol 283-286 ◽  
pp. 419-424
Author(s):  
Lucia Suarez ◽  
Pablo Rodriguez-Calvillo ◽  
Rafael Colás ◽  
Yvan Houbaert
Keyword(s):  
Oxide Scale ◽  
Plane Strain ◽  
Oxide Layer ◽  
Hot Rolling ◽  
Protective Atmosphere ◽  
Phase Identification ◽  
Oxide Scales ◽  
Orientation Relationships ◽  
Complex Deformation ◽  
Ebsd Technique

Oxide scales growing during hot rolling of steel represent an industrial and environmental problem. Tertiary oxide, which starts to form before entering the finishing stands, remains on the steel surface until the end of the process, affecting the final surface quality and the response to downstream processing. Characterizing scale layers and the scale/steel interface in terms of phase morphology, texture, grain structure and chemical composition is fundamental for a better understanding of their behaviour and the effect of thermomechanical cycles on the material response to further processing. Thin tertiary scale layers have been grown on ULC steel under controlled conditions in a laboratory device adequately positioned in a compression-testing machine, immediately before plane strain deformation. After heating under a protective atmosphere (nitrogen), the samples have been oxidized in air at 1050°C for a short oxidation time. Immediately after this controlled oxidation, some of the samples were subjected to plane strain compression (PSC) inside the experimental device, in order to simulate the finishing hot rolling process. Direct observations of oxide scale layers are impossible. The EBSD technique has been identified as a powerful tool that can be used to reveal the microstructure within the oxide scale and to distinguish between its constitutive phases, based on their distinct crystal lattices. The texture of the deformed oxide scales, originally grown on ULC steel, was determined in a SEM using the EBSD technique. This will help to achieve a better understanding of their complex deformation behaviour. Because the substrate deformation affects the oxide layer, orientation relationships between scale layer and substrate were measured and the crystallographic orientation between undeformed and deformed areas was determined. Strongly textured wustite grains with a clearly pronounced columnar structure were observed after oxidation at 1050°C. The detailed EBSD study reveals that the oxide layer is able to accommodate a significant amount of deformation.

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