Thermochemistry and the Oxidation of Refractory Metals at High Temperature

CORROSION ◽  
1970 ◽  
Vol 26 (1) ◽  
pp. 19-28 ◽  
Author(s):  
EARL A. GULBRANSEN
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Refractory Metals ◽  
Melting Points ◽  
Temperature Oxidation ◽  
Volatile Oxide ◽  
Oxidation Processes ◽  
Recent Developments ◽  
Oxide Phases ◽  
The One

Abstract Recent developments in the thermochemical data for the condensed oxide phases and volatile oxide species for the refractory metals has made possible an analysis of the several types of high temperature oxidation processes. The analyses show the following factors to be important: (1) the presence or absence of oxide films or scales on the metals, (2) the melting points of the one or more oxide phases, (3) the equilibrium pressures of the several volatile oxides, and (4) the flow rate of reactant gases. The thermochemical predictions are compared to experimental observations for molybdenum and tungsten.

High Temperature Erosion-Corrosion in Gas Turbines

1982 ◽  
Author(s):  
J. Stringer
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
High Temperature Oxidation ◽  
Metal Loss ◽  
Protective Oxide ◽  
Temperature Oxidation ◽  
Oxidation Processes ◽  
Erosion Corrosion ◽  
Burning Coal ◽  
High Temperature Erosion

Under certain circumstances, hot gases containing particulates may be expanded through a turbine. The erosion damage due to the particulates interacts with the high temperature oxidation processes. The interaction may be positive: the oxide layer may be more erosion-resistant than the substrate. The interaction may be negative: the erosion can remove the protective oxide resulting in accelerated metal loss. If the gases contain corrosive materials such as alkali sulfates as well as the particulates, further interactions are possible. These processes are of importance in gas turbine expanders for pressurized fluidized bed combustors burning coal, and several research projects are in progress to study them.

Oxidation Behavior of some Refractory Metals and Compounds

2011 ◽  
Vol 696 ◽  
pp. 354-359 ◽  
Author(s):  
Bulent Önay
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Transportation Systems ◽  
Refractory Metals ◽  
Transition Elements ◽  
Aerospace Vehicles ◽  
Temperature Oxidation ◽  
New Class ◽  
Melting Temperatures ◽  
Oxidation Properties

Engineering materials with better high temperature oxidation properties are needed to increase the thermodynamic efficiencies of the energy production and transportation systems. Because of their high melting temperatures, refractory metals like Nb or Mo are brought together with intermetallic compounds as two components of a new class of composite materials. To acquire a balanced high temperature mechanical and oxidation properties, these materials generally have multiphase and multicomponent structures. Borides of some transition elements are also being considered as high temperature structural materials for new aerospace vehicles. These materials are also required to have sufficient high temperature oxidation resistance in order to provide reliable and long service lives.

The Thermal Cyclic Behavior of the VPS and HVOF-Sprayed MCrAlY Coatings

2006 ◽  
Vol 326-328 ◽  
pp. 1141-1144 ◽  
Author(s):  
Jine Sung Jung ◽  
Keun Bong Yoo ◽  
Eui Hyun Kim ◽  
Chae Hong Jeon ◽  
Do Hyang Kim
Keyword(s):  
High Temperature ◽  
Bond Coat ◽  
High Temperature Oxidation ◽  
Ambient Air ◽  
Cyclic Behavior ◽  
Vacuum Plasma Spray ◽  
Temperature Oxidation ◽  
Nickel Based Superalloy ◽  
Oxide Phases ◽  
Coating Characteristics

Rotating components used in the hot sections of land-based gas turbine are exposed to severe environment of several ten thousands operating hours above 1100. To protect such components against high temperature oxidation an intermediate bond coat is applied, typical of a MCrAlY-type metal alloy. Various processing methods have been studied for bond coat deposition. This study is concerned with the cyclic oxidation behavior of CoNiCrAlY coatings. Coatings were deposited by a vacuum plasma spray and high-velocity oxygen fuel method on a nickel-based superalloy (GTD-111). Cyclic thermal oxidation test condition is at 1100 in ambient air for various periods of time. Tests were used to evaluate the oxidation resistance of the spray-coated specimens. The microstructure and morphology of as-sprayed and of tested specimens were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The oxide phases formed on the coating surface are NiO, CoCr2O4, and Al2O3. The nickel oxide of them was to be dominant with increasing cycles. The differences in microstructure and phase composition in the interface with coating layer are reported. The influence of coating process methods on coating characteristics and degradation mechanisms is discussed. The HVOF coating with the splats was more resistant on the high temperature oxidation than the VPS coating.

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