scholarly journals Oxidation of Ni-Cr-Co-Al-Mo-Ti-Re-Ta-W-Ru Single Crystals at 1000 oC in Air

2020 ◽  
Vol 58 (4) ◽  
pp. 234-246 ◽  
Author(s):  
Junhee Hahn ◽  
Xiao Xiao ◽  
Dong Bok Lee
Keyword(s):  
Single Crystals ◽  
Oxidation Resistance ◽  
Oxide Scales ◽  
Al2o3 Scale ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Active Elements ◽  
Al2o3 Scales ◽  
Cast Alloys ◽  
Α Al2o3

Three kinds of Ni-based single crystals with the compositions of 63.8Ni-7.5Cr-5.1Co-4.8Al-1.9Mo- 0.9Ti-3Re-11.8Ta-1.2W, 61.4Ni-7.4Cr-5Co-4.8Al-1.8Mo-0.9Ti-3.1Re-11.6Ta-4W, and 60.9Ni-7.5Cr-5Co-4.8Al- 2Mo-1Ti-2.9Re-10.9Ta-1.2W-3.8Ru, in wt%, were cast in a Bridgman furnace. In the cast alloys, Cr, Co, Re, Mo, W, and Ru became microsegregated in dendrites consisting of γ-Ni, while Ni, Ta, and Al microsegregated in interdendrites consisting of eutectic γ/γ . The cast alloys were oxidized at 1000 oC up to 275 h in air to study the effect of alloying elements on high-temperature oxidation. The oxide scales consisted primarily of CrTaO4, with some NiCr2O4, NiO, and α-Al2O3. The oxidation resistance was dependent on the formation and continuity of the α-Al2O3 scale. Ta and W were beneficial, while Ru was harmful in improving the oxidation resistance. The selective oxidation of Al in dendrites led to the formation of thin, uniform α-Al2O3 scales, i.e., uniform oxidation. The competitive oxidation of active elements such as Al, Ti, and Ta in interdendrites led to the formation of porous, crack-susceptible oxide nodules, i.e., nodular oxidation. Less active elements such as Ru, Re, Ni, Co, Mo, W, and Cr tended to enrich in the vicinity of the oxide nodules. The oxidation progressed through the outward diffusion of cations and the inward diffusion of oxygen. This inward diffusion formed internal alumina islands, beneath the oxide scale.

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 Behavior of TiNi Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 853-856 ◽  
Author(s):  
J.H. Ko ◽  
Dong Bok Lee
Keyword(s):  
Oxidation Behavior ◽  
Oxidation Mechanism ◽  
Tini Alloy ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Ni Alloy ◽  
Embedded Particles ◽  
High Temperature Oxidation Behavior ◽  
Better Than

The oxidation behavior of the equiatomic TiNi alloy was investigated at 600-900oC. The oxidation resistance of the TiNi alloy was better than the pure Ti alloy, but worse than the pure Ni alloy. The oxide scales consisted of TiO2, with and without embedded particles of TiNiO3 and Ni. The subscale matrix phase was (TiNi3+TiNi) at 600oC, TiNi3 at 700oC, (Ni+TiNi3) at 800oC, and Ni at 900oC. Oxidation was mainly governed by the inward diffusion of oxygen, and the outward diffusion of Ti and a bit of Ni. Detailed microstructures and the oxidation mechanism are proposed.

Oxidation Behavior of K38 Superalloy with Different Amounts of Yttrium Addition at 1173K in Air

2011 ◽  
Vol 366 ◽  
pp. 40-44 ◽  
Author(s):  
Ping Yu ◽  
Long Shi ◽  
Wen Wang ◽  
Fu Hui Wang
Keyword(s):  
Oxidation Resistance ◽  
Selective Oxidation ◽  
Internal Oxidation ◽  
Oxidation Rate ◽  
Oxidation Behavior ◽  
Rich Phase ◽  
Al2o3 Scales ◽  
Yttrium Addition ◽  
Negative Effect ◽  
Cast Alloys

The oxidation behavior of K38 alloy with 0, 0.05, 0.1, 0.5wt% yttrium concentrations has been investigated during exposures in air at 1173K for 100 hours. The results indicated that Cr2O3 and TiO2 scale mainly formed on the surface of the alloy without yttrium. Yttrium addition promoted the selective oxidation of aluminum and reduced the internal oxidation. The alloy with 0.1 wt.% yttrium addition exhibits excellent oxidation behavior among the four types of the alloys for its decreasing the oxidation rate and forming more continuous and compact Al2O3 scales. Yttrium-rich phase formed in the alloy with 0.5wt.% yttrium, result in a negative effect on the oxidation resistance of cast alloys.

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.

Study on Improvement of Oxide Layer and Properties of Plasma Sprayed Alumina in Thermal Barrier Coatings

2007 ◽  
Vol 127 ◽  
pp. 313-318 ◽  
Author(s):  
Akira Kobayashi ◽  
G. Shanmugavelayutham ◽  
S. Yano
Keyword(s):  
Mechanical Properties ◽  
Oxidation Resistance ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Potential Candidate ◽  
Low Oxygen ◽  
Temperature Oxidation ◽  
Barrier Coatings ◽  
Turbine Engine ◽  
Α Al2o3

Thermal barrier coatings (TBC) have been used to improve the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating. TBC failure occurs easily at the interface between the metallic bondcoat and topcoat. Alumina was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating due to its low oxygen diffusivity against the harsh environment. The mechanical properties, thermal behaviour and high temperature oxidation resistance of the coatings formed by gas tunnel type plasma spraying were investigated in this study. The results showed that this system exhibits the improvement of mechanical properties of the coating and oxidation resistance. This interlayer is preferred in order to minimize the detrimental effect of phase transformation of γ- Al2O3 to α-Al2O3.

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.

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.

scholarly journals Oxide Spallation During Post-isothermal High Temperature Oxidation Cooling of Cr-rich Cast Alloys Highly Alloyed with Hf

2016 ◽  
Vol 10 (1) ◽  
pp. 89-100 ◽  
Author(s):  
Elodie Conrath ◽  
Patrice Berthod
Keyword(s):  
Oxide Scales ◽  
Scale Spallation ◽  
Complex Composition ◽  
Temperature Oxidation ◽  
Cobalt Nickel ◽  
Major Parameter ◽  
Cast Alloys ◽  
Oxide Spallation ◽  
Iron Based ◽  
Cooling Part

Cobalt, nickel and iron-based alloys containing 25wt.%Cr and strengthened either by chromium carbides or by HfC were oxidized at 1000, 1100 and 1200°C to obtain external oxide scales. The spallation of these oxides during the post-oxidation cooling was studied by exploiting the cooling part of the thermogravimetry curves. The best resistant alloys against scale spallation were the iron-based alloys which did not lose oxide. The nickel-based alloys well behaved too. The worst alloys were the cobalt alloys, principally due to the complex composition of the oxide scales. Beside the base element, the thickness of the oxide was also identified as a major parameter. The presence of Hf with contents much higher than usual was also beneficial for the resistance against spallation.

Preparation and Oxidation Behaviour of an Al-Si Coating on a Ni3Al Based Single Crystal Superalloy IC21

2013 ◽  
Vol 747-748 ◽  
pp. 575-581 ◽  
Author(s):  
Yu Zhuo Liu ◽  
Qiong Wu ◽  
Shu Suo Li ◽  
Yue Ma ◽  
Sheng Kai Gong
Keyword(s):  
Phase Transformation ◽  
Oxidation Resistance ◽  
Outer Layer ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Oxidation Behaviour ◽  
Oxide Scales ◽  
Outward Diffusion ◽  
Microstructure Change ◽  
Β Phase

An Al-Si coating was prepared on IC21 alloy by powder pack cementation. The cyclic oxidation tests were carried out at 1150 in air for up to 100 h. The results indicate that the oxidation resistance of IC21 alloy is significantly improved by the Al-Si coating due to the presence of Ni2Al3and β-NiAl enriched outer layer, and Si can effectively supress the outward diffusion of Mo. The oxide scales mainly consist of α-Al2O3, which is the favorite to the oxidation resistance. Phase transformation occurred from β-NiAl to γ-Ni3Al and γ-Ni in the coating during oxidation. The coating still remained a certain amount of β phase after oxidation for 100h, which indicate a good protection. The microstructure change evolution was characterized, and the oxidation behavior of the coating was discussed.

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.

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