Edge-on TEM studies of oxide scale formation on FeNiCr alloys

1984 ◽  
Vol 42 ◽  
pp. 612-615
Author(s):  
S.B. Newcomb
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Lattice Diffusion ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Temperature Growth ◽  
Good Oxidation Resistance ◽  
Thermally Activated ◽  
Chromium Alloys ◽  
State Scale

The high temperature oxidation resistance of many commercial alloy systems is often reliant upon the development of a steady state scale via the selective oxidation of one of the alloy constituents. The growth of adherent chromiumrich sesquioxides on iron-chromium alloys, for example, imparts good oxidation resistance although steels of low chromium content (< 13wt%) generally form thick layered scales which may breakdown after extended periods giving rise to accelerated rates of oxidation. The high temperature growth process essentially proceeds thermally activated transport and may involve either the outward diffusion of cations and/or the inward migration of anions. Typically, solid state diffusional transport will take place by lattice diffusion or by transport along grain boundaries so that the overall rate of transport is an inherent property of the oxide structure and composition. Equally, the morphology of the oxide itself will be determined by a variety of kinetic and thermodynamic factors.

High Temperature Oxidation of Ti45.4Al4.8Nb and Ti46Al2Mo2Nb Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 801-804
Author(s):  
J.W. Kim ◽  
Dong Bok Lee
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Middle Layer ◽  
Tio2 Layer ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Oxidation Characteristics ◽  
Dissolved Ions

The Ti46Al2Nb2Mo and Ti45.4Al4.8Nb alloys were oxidized isothermally and cyclically in air between 800 and 1000oC, and their oxidation characteristics were investigated. Nb and Mo were beneficial to oxidation resistance. The initially formed thin TiO2-rich scale changed to an outer, superficial TiO2 layer, a thick Al2O3-rich middle layer, and an inner (TiO2-rich, Al2O3-deficient) layer, as the extent of oxidation progressed. The dissolved ions of Mo and Nb had a tendency to be expelled from the outer TiO2 layer, which was formed by the outward diffusion of Ti ions, to the inner (TiO2-rich, Al2O3-deficient) layer, which was formed by the inward transport of oxygen, owing to the nobility of Mo and Nb when compared to Ti and Al.

scholarly journals High Temperature Oxidation Behaviors of BaO/TiO2 Binary Oxide-Enhanced NiAl-Based Composites

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6510
Author(s):  
Bo Li ◽  
Ruipeng Gao ◽  
Hongjian Guo ◽  
Congmin Fan
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Mechanism ◽  
High Tech ◽  
Slight Reduction ◽  
Application Process ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Resistance Performance

High temperature lubricating composites have been widely used in aerospace and other high-tech industries. In the actual application process, high temperature oxidation resistance is a very importance parameter. In this paper, BaO/TiO2-enhanced NiAl-based composites were prepared by vacuum hot-press sintering. The oxidation resistance performance of the composites at 800 °C was investigated. The composites exhibited very good sintered compactness and only a few pores were present. Meanwhile, the composite had excellent oxidation resistance properties due to the formation of a dense Al2O3 layer which could prevent further oxidation of the internal substrate; its oxidation mechanism was mainly decided by the outward diffusion of Al and the inward diffusion of O. The addition of BaO/TiO2 introduced more boundaries and made the Kp value increase from 1.2 × 10−14 g2/cm4 s to 3.3 × 10−14 g2/cm4 s, leading to a slight reduction in the oxidation resistance performance of the composites—although it was still excellent.

Structure and High-Temperature Oxidation of Ti-Al-Nb and Ti-Al-Ta Intermetallics

2011 ◽  
Vol 465 ◽  
pp. 227-230 ◽  
Author(s):  
Dalibor Vojtěch ◽  
Tomáš Popela
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Oxidation Mechanism ◽  
High Strength ◽  
Vacuum Arc ◽  
Temperature Oxidation ◽  
Good Oxidation Resistance ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Work Structure

Ti-Al based intermetallics are prospective high-temperature materials showing low weight combined with a relatively high strength, high creep resistance and good oxidation resistance at high temperatures. Beside Ti and Al, these materials commonly contain other additives modifying their properties. In the present work, structure and oxidation resistance of two Ti-Al-Nb and Ti-Al-Ta alloys are studied. The alloys are prepared by vacuum arc melting and oxidation is conducted in air at 800-1000°C. It is found that there are significant differences in the structure depending on the ternary additive. There are also differences in oxidation behavior and these differences are discussed in relation to oxidation mechanism.

HIGH-TEMPERATURE OXIDATION OF HOT-DIP ALUMINIZED P23 STEEL

2019 ◽  
Vol 27 (05) ◽  
pp. 1950153
Author(s):  
DONG BOK LEE ◽  
JUNHEE HAHN ◽  
MUHAMMAD ALI ABRO
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Formation Of Cracks

ASTM P23 steel (Fe-2.25Cr-1.6W-0.1Mo in wt.%) was hot-dip aluminized and oxidized at 800∘C and 1000∘C for 20 h in air in order to determine the effect of aluminizing on the microstructure, hardness, and oxidation resistance of P23 steel. Aluminizing effectively increased the oxidation resistance of P23 steel by forming protective [Formula: see text]-Al2O3 scales. During oxidation, outward diffusion of substrate elements and inward transport of Al and oxygen occurred simultaneously. The oxidation and interdiffusion formed voids in the coating, lowered the microhardness, and transformed the original (Al-rich topcoat)/(Al[Formula: see text]Fe4 layer) to either (thin [Formula: see text]-Al2O3 scale)/(Al5Fe2 layer)/(AlFe layer)/(AlFe3 layer)/([Formula: see text]-Fe(Al) layer) at 800∘C or (thick [Formula: see text]-Al2O3 scale)/(AlFe3 layer)/([Formula: see text]-Fe(Al) layer) at 1000∘C. At 1000∘C, Fe2O3 was also formed in addition to [Formula: see text]-Al2O3 scale, due to the enhanced outward diffusion of Fe, thus suppressing the formation of cracks in the coating.

State of the Art and Prospects on Laser Clad Multiphase Transition Metal Silicides Wear and Corrosion Resistant Coatings for the Aerospace and Petrochemical Industries

2006 ◽  
Vol 118 ◽  
pp. 235-242 ◽  
Author(s):  
H.M. Wang ◽  
L.X. Cai
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Oxidation Resistance ◽  
Fretting Wear ◽  
Temperature Oxidation ◽  
Corrosion Resistant ◽  
Good Oxidation Resistance ◽  
Test Conditions ◽  
Metal Silicides ◽  
Wear And Corrosion

Wear and corrosion resistant multi-phase transition metal silicides coatings including W2Ni3Si/W5Si3, Ti5Si3/NiTi2, Ti2Ni3Si/NiTi, etc, were developed and fabricated by laser cladding process. Tribological properties were evaluated under dry sliding and reciprocating fretting wear test conditions and the responding wear mechanisms were discussed as functions of microstructure constitutions and test conditions. High temperature oxidation resistance of the coatings was investigated. The coatings exhibited excellent combination of room and high temperature metallic sliding wear resistance, fretting propertiy, metallic tribological compatibility, good oxidation resistance and abnormal wear-load dependence. Applications of the coatings were prospected for the aerospace, petrochemical and energy-processing industries.

High Temperature Oxidation of Ti39.4Al10V Alloy

2004 ◽  
Vol 449-452 ◽  
pp. 813-816 ◽  
Author(s):  
Dong Bok Lee ◽  
Y.D. Jang
Keyword(s):  
High Temperature ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Mixed Layer ◽  
High Temperature Oxidation ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Outward Diffusion

Alloys of Ti39.4Al10V (at.%) that consisted mainly of ordered β-Ti, γ-TiAl and α2-Ti3Al phases were oxidized at 700, 800, 900, and 1000oC in air. The oxide scales formed consisted largely of an outermost, thin TiO2 layer, an outer, thin Al2O3 layer, and an inner, very thick (TiO2+Al2O3) mixed layer. Vanadium, which was uniformly distributed throughout the oxide scale, harmfully decreased oxidation resistance, and made thick, nonadherent scales owing to the formation of low melting compounds of V-oxides. The oxidation progressed via the outward diffusion of Ti, Al and V ions, and the concurrent inward transport of oxygen.

High Temperature Oxidation of Electroplated Cr-C Coating

2006 ◽  
Vol 510-511 ◽  
pp. 418-421 ◽  
Author(s):  
Dong Bok Lee ◽  
Sik Chol Kwon
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Microcrystalline Structure ◽  
Temperature Oxidation ◽  
Good Oxidation Resistance

The oxidation of Cr-12.7 at.%C coatings electrodeposited on steel was studied at 700 and 800oC in air. The coatings, which consisted of nodular grains having microcracks and pits, had either an amorphous or a microcrystalline structure. They changed to crystalline Cr during oxidation. The oxidation resulted in the formation of Cr2O3, which provided good oxidation resistance to the coating. However, the presence of microcracks and pits in the coating was harmful to oxidation resistance.

High Temperature Oxidation Behaviors of CNTs/MoSi2 Composites

2014 ◽  
Vol 487 ◽  
pp. 15-19
Author(s):  
He Jian Wu ◽  
Hou An Zhang ◽  
Si Yong Gu ◽  
Jia Lin
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Molybdenum Disilicide ◽  
Protective Film ◽  
Matrix Composites ◽  
Temperature Oxidation ◽  
Good Oxidation Resistance ◽  
Gaseous Products ◽  
Oxidation Behaviors

Molybdenum disilicide (MoSi2) matrix composites with various contents of carbon nanotubes (CNTs) were fabricated by sintering in vacuum at 1550°C for 1 h. The oxidation behaviors of CNTs/MoSi2composites at 1300°C for 200 h in air were studied. Results showed that MoSi2matrix composites with no more than 8 % CNTs in volume had good oxidation resistance at 1300 °C, although addition of CNTs reduced the high temperature oxidation resistance of MoSi2. An approximate linear relationship was found between the weight gain of CNTs/MoSi2composites and the content of CNTs. The oxidation resistance of CNTs/MoSi2composites at high temperature decreased with the increasing of CNTs contents. Since the gaseous products were formed during the oxidation process and escaped from the oxide film, the protective film became loose which offered channels for the oxygen soaking into the composites. Thus the oxidation resistance of CNTs/MoSi2composites was decreased.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

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