High Temperature Oxidation in Multicomponent Nb Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 717-720 ◽  
Author(s):  
E. Sarath K. Menon ◽  
Madan G. Mendiratta
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Material System ◽  
Silicon Alloys ◽  
Temperature Oxidation ◽  
Multiphase Alloys ◽  
Temperature Capability ◽  
New Generation ◽  
Poor Oxidation Resistance

Niobium-Silicon alloys offer potential as a new generation of refractory material system that could meet the high-temperature capability envisaged to exceed the application temperatures of Ni base superalloys. A serious concern in the application of Nb based alloys is their poor oxidation resistance at elevated temperatures. The ternary diagram Nb-Ti-Si system exhibits eutectic groves nearly parallel to the Nb-Ti binary and terminate in a Class II invariant reaction, L+(Nb,Ti)3Si → β+ (Ti,Nb)5Si3. A peretectic ridge from the reaction, L+(Nb,Ti)5Si3 →(Nb,Ti)3Si also exists and these reactions control the microstructures resulting from solidification of these Nb alloys. The microstructures associated with these alloys comprise a distribution of Nb5Si3 in β matrix. The effect of various alloying elements on the resulting microstructures are illustrated The effect of microstructural distribution on oxidation resistance of multiphase alloys are also discussed.

The Investigation of the Interdiffusion Barrier in TiAl/MCrAlY System

2010 ◽  
Vol 654-656 ◽  
pp. 1920-1923 ◽  
Author(s):  
Wen Wang ◽  
Yu Xian Cheng ◽  
Sheng Long Zhu ◽  
Fu Hui Wang ◽  
Li Xin
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Diffusion Barrier ◽  
High Temperature Oxidation ◽  
Temperature Oxidation ◽  
The Poor ◽  
Structural Applications ◽  
Nicraly Coating ◽  
Overlay Coatings ◽  
Poor Oxidation Resistance

TiAl based alloys are promising candidates for structural applications at high temperature. However, the poor oxidation resistance above 800oC obviously restrains their applications. Although NiCrAlY overlay coatings can remarkably improve the high temperature oxidation resistance of TiAl, serious inward diffusion of Ni from the coating to the substrate occurs which could reduce the lifetime of the coating/substrate system. Apparently, the development of interdiffusion barrier could overcome the disadvantage of the NiCrAlY/TiAl system. In this work, Ta, TiN and Cr2O3 interlayers were deposited between NiCrAlY coating and γ-TiAl substrate as diffusion barrier (DB). The interdiffusion behavior of the TiAl/DB/NiCrAlY system was investigated at 1000°C. The results showed that the metallic and nitride interlayers cannot retard the interdiffusion of Ni effectively. As an active diffusion barrier, the oxide interlayer obviously suppressed the inward diffusion of Ni from the coating to the substrate by the formation of alumina-rich layers at both the TiAl/DB and DB/NiCrAlY interfaces.

Comparison of Different Fluorine-treatments for Improved High Temperature Oxidation Resistance of TiAl-alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
A. Donchev ◽  
M. Schütze ◽  
A. Kolitsch ◽  
R. Yankov
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Fluorine Content ◽  
Intermediate Formation ◽  
Experimental Investigations ◽  
Alumina Layer ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
Al Content

ABSTRACTIntermetallic TiAl-alloys can replace the heavier Ni-based superalloys in several high temperature applications with regards to their mechanical properties, however they can not be used at temperatures above 800°C in oxidizing environments for longer times because of insufficient oxidation resistance. Despite an Al-content of about 45 at.% in technical alloys, no protective alumina layer is formed because the thermodynamic stabilities of titanium oxide and aluminum oxide are of the same order of magnitude. Therefore a mixed TiO2/Al2O3-scale is formed which is fast growing so that the metal consumption rate is quite high. On the other hand the formation of a slow growing alumina layer is promoted by a fluorine treatment. This so called fluorine effect leads to the preferential intermediate formation of gaseous aluminum fluorides at elevated temperatures if the fluorine content at the surface stays within a defined concentration range. These fluorides are converted into solid Al2O3 due to the high oxygen partial pressure of the high temperature service environment forming a protective pure Al2O3 surface scale. In this paper results of high temperature oxidations tests of several technical TiAl-alloys will be presented. Different F-treatments e.g. dipping or spaying which are easy to apply have been used and their results will be compared. The mass change data of the F-treated specimens are always lower than those of the untreated ones. Post experimental investigations such as light microscopy, scanning electron microscopy and energy dispersive X-ray analysis reveal the formation of a thin alumina layer on the F-treated samples after optimization of the process while a thick mixed scale is found on the untreated samples. The results will be discussed in view of an optimized procedure and the future use of TiAl-components in high temperature environments.

Economic Surface Treatment of Ti-Alloys to Improve their Resistance against Environmental High Temperature Attack

2013 ◽  
Vol 551 ◽  
pp. 109-113 ◽  
Author(s):  
Alexander Donchev ◽  
Michael Schütze ◽  
Andreas Kolitsch ◽  
Rossen Yankov
Keyword(s):  
High Temperature ◽  
Surface Treatment ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Surface Region ◽  
Alumina Scale ◽  
Ti Alloys ◽  
Temperature Capability ◽  
Temperature Exposure ◽  
Al Treatment

High temperature Ti-alloys are usually sophisticated and hence expensive. To allow the use of cheaper alloys at elevated temperatures an economic and easy to apply procedure was developed to improve their high temperature capability. The treatment consists of a combination of Al-enrichment in a shallow surface region plus additional fluorination. The Al-enrichment at elevated temperatures leads to the formation of intermetallic TiAl-phases. These phases improve the oxidation resistance of Ti-alloys but not to a sufficient extent. An additional fluorine treatment of the Al-enriched surface leads to the formation of a protective alumina scale due to the fluorine effect. In this paper results from high temperature exposure tests performed on different Ti-alloys without any treatment and with a combination of Al-treatment plus fluorination are presented. The results are discussed in the view of the use of the optimized Ti-components for several high temperature applications.

High Temperature Oxidation Protection of Multi-Phase Mo-Containing TiAl-Alloys by the Fluorine Effect

2012 ◽  
Vol 1516 ◽  
pp. 95-100 ◽  
Author(s):  
Alexander Donchev ◽  
Raluca Pflumm ◽  
Svea Mayer ◽  
Helmut Clemens ◽  
Michael Schütze
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Titanium Aluminides ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Temperature Oxidation ◽  
Tial Alloys ◽  
Β Phase ◽  
Multi Phase ◽  
The Impact

ABSTRACTIntermetallic titanium aluminides are potential materials for application in high temperature components. In particular, alloys solidifying via the β-phase are of great interest because they possess a significant volume fraction of the disordered body-centered cubic β-phase at elevated temperatures ensuring good processing characteristics during hot-working. Nevertheless, their practical use at temperatures as high as 800°C requires improvements of the oxidation resistance. This paper reports on the fluorine effect on a multi-phase TiAl-alloy in the cast and hot-isostatically pressed condition at 800°C in air. The behavior of the so-called TNM material (Ti-43.5Al-4Nb-1Mo-0.1B, in at %) was compared with that of two other TiAl-alloys which are Nb-free and contain different amounts of Mo (3 and 7 at%, respectively). The oxidation resistance of the fluorine treated samples was significantly improved compared to the untreated samples. After fluorine treatment all alloys exhibit slow alumina kinetics indicating a positive fluorine effect. Results of isothermal and thermocyclic oxidation tests at 800°C in air are presented and discussed in the view of composition and microstructure of the TiAl-alloys investigated, along with the impact of the fluorine effect on the oxidation resistance of these materials.

High-Temperature Oxidation of WC-20%TiC-10%Co Carbides

2013 ◽  
Vol 811 ◽  
pp. 93-97 ◽  
Author(s):  
Yeon Sang Hwang ◽  
Dong Bok Lee
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxide Scales ◽  
Temperature Oxidation ◽  
Large Weight ◽  
Oxidation Characteristics ◽  
Weight Gains ◽  
Poor Oxidation Resistance

The oxidation characteristics of WC-20%TiC-10%Co sintered carbides were studied by oxidizing at 700, 800 and 900 °C for 3 h in air. The samples oxidized fast with large weight gains, displaying quite poor oxidation resistance. The formed oxide scales that consisted primarily of CoWO4, WO3, and TiO2 were porous, and prone to cracking.

High-Temperature Oxidation Resistant Nanocoatings on Austenitic Stainless Steels

2009 ◽  
Vol 1243 ◽  
Author(s):  
Hugo F. Lopez
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
High Efficiency ◽  
Elevated Temperatures ◽  
Clean Energy ◽  
Ceramic Coatings ◽  
Energy Utilization ◽  
Weight Changes ◽  
Temperature Oxidation

ABSTRACTIn recent years, the increasing energy costs have lead to power utility industries to seek/develop high efficiency systems of production and of energy utilization. In addition, environmental concerns regarding greenhouse gas emissions are playing a major role in the development of clean energy systems. The development of metallic materials that can withstand elevated temperatures is among the viable alternatives to increase energy efficiency. Nevertheless, for this to happen, the corrosion and oxidation resistance of Fe- and Ni-based alloys needs to be significantly improved. Among the possible ways to enhance the life of high temperature alloys is the application of protective ceramic coatings. Conventional coatings are expensive and the protective effects controversial at times. An alternative which offers a great potential is the application of nano-ceramic coatings. Hence, in this work nanocrystalline coatings based on nano-CeO2 are applied to an austenitic stainless steel 304L and then exposed to elevated temperatures. Weight changes are monitored as a function of time and the results are compared with uncoated alloys tested under similar conditions. In addition, computer simulations of possible rate limiting diffusion mechanisms are carried out. It is found that the nanocoatings provided remarkable high-temperature oxidation resistance and improved scale adhesion. In particular, it is found that the smaller the nanoparticles are, the more effective the nanocoatings in providing oxidation resistance.

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.

High-temperature oxidation resistance behavior of porous Ni-16Cr-9Al materials

2019 ◽  
Vol 110 (10) ◽  
pp. 969-978 ◽  
Author(s):  
Liang Wu ◽  
Ge Yang ◽  
Yang Xu ◽  
Yifeng Xiao ◽  
Xi Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Temperature Oxidation

AK STEEL 441

Alloy Digest ◽  
2006 ◽  
Vol 55 (6) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Tensile Properties ◽  
Oxidation Resistance ◽  
Ferritic Stainless Steel ◽  
High Temperature Oxidation ◽  
High Temperature Strength ◽  
Temperature Oxidation ◽  
Temperature Performance

Abstract AK Steel 441 has good high-temperature strength, an equiaxed microstructure, and good high-temperature oxidation resistance. The alloy is a niobium-bearing ferritic stainless steel. This datasheet provides information on composition, hardness, and tensile properties as well as deformation. It also includes information on high temperature performance and corrosion resistance as well as forming and joining. Filing Code: SS-965. Producer or source: AK Steel.

High-Temperature Oxidation Resistance and Thermal Stability of Higher Manganese Silicide Powder Synthesized by Pack Cementation

2021 ◽  
pp. 159842
Author(s):  
Aikaterini Teknetzi ◽  
Evangelia Tarani ◽  
Dimitrios Stathokostopoulos ◽  
Dimitrios Karfaridis ◽  
Konstantinos Chrissafis ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Pack Cementation ◽  
Higher Manganese Silicide ◽  
Temperature Oxidation ◽  
Manganese Silicide ◽  
Thermal Stability Of
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