EXPERIMENTAL STUDY OF FACTORS CONTROLLING THE EFFECTIVENESS OF HIGH- TEMPERATURE PROTECTIVE COATING FOR TUNGSTEN

Technical Report · Mon Jul 15 00:00:00 EDT 1963

OSTI ID:4154414

Dickinson, C D; Seigle, L L

The oxidation at elevated temperatures of Zr-- Th, Zr-- Y, Hf--Y, Hf--W, Hf--W-Re, Al--Cr--Sn, and Al-- La--Sn alloys, as well as ZrN, HfN, and ZrN-- ThN combinations has been studied in order to clarify specific aspects of the problem of protecting tungsten against oxidation at high temperatures. Experimental results showed that there was much less tendency for ZrO/sub 2/, ThO/sub 2/, and HfO/sub 2/ scales to crack during growth at high thand at low temperatures. Furthermore, multiphased scales were more resistant to spalling than single- phased scales, and protective oxides could be grown on many alloys. However, even in sound and coherent scales composed of these oxides, oxygen diffused so rapidly that it is doubtful that these oxides could form the basis of a protective system at 2000 deg C. The sequence of layers at the metal-air interface of the Zr--Th and Zr--Y alloys formed by diffusion-controlled oxidation was governed by a simple rule; namely, that the diffusion path in the appropriate isothermal section of the ternary equilibrium diagram is a straight line connecting the alloy composition with the oxygen conner. This rule is expected to apply to all ternary systems in which the oxidation process is dominated by the rapid diffusion of oxygen atoms in all layers. If significandt migration of cations occurs, however, the rule is not applicable. Observations have been made of the rate of formation, nature, and morphology of scales formed on the brittle refractory compounds W/sub 2/Hf, ZrN, HfN, and ZrN-- ThN, and those formed on liquid Zr-- Y, Al-Cr-- Sn and Al-- Ra-- Sn alloys. These observations are discussed in terms of their implications for the development of oxidation protection systems for tungsten at high temperatures. (auth)

• Research Organization: General Telephone and Electronics Lab., Inc., Bayside, N.Y.
• DOE Contract Number: AF33(657)-8787
• NSA Number: NSA-18-005729
• OSTI ID: 4154414
• Report Number(s): ASD-TDR-63-744
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-64
• Country of Publication: United States
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
ALLOTROPY
ALUMINUM ALLOYS
CHROMIUM ALLOYS
COATING
CORROSION PROTECTION
CRACKS
DIFFUSION
HAFNIUM ALLOYS
HAFNIUM NITRIDES
HAFNIUM OXIDES
HIGH TEMPERATURE
INTERMETALLIC COMPOUNDS
LANTHANUM ALLOYS
LIQUID METALS
LOW TEMPERATURE
OXIDATION
OXYGEN
RHENIUM OXIDES
THORIUM ALLOYS
THORIUM NITRIDES
THORIUM OXIDES
TIN ALLOYS
TUNGSTEN
TUNGSTEN ALLOYS
YTTRIUM ALLOYS
ZIRCONIUM ALLOYS
ZIRCONIUM NITRIDES
ZIRCONIUM OXIDES