ARMED SERVICES TECHNICAL INFORMATION …

1 UNCLASSIFIED 69J73 RepAaduced luf tin ARMED SERVICES TECHNICAL INFORMATION agency arlington HALL STATION arlington 12, VIRGINIA UNCLASSIFIED THIS DOCUMENT IS BEST QUALITY AVAILABLE. THE COPY FURNISHED TO DTIC CONTAINED A SIGNIFICANT NUMBER OF PAGES WHICH DO NOT REPRODUCE LEGIBLYo NOTICE: When government or other drawings, speci- fications or other data are used for any purpose other than in connection with a definitely related government procurement operation, the U. S. Government thereby incurs no responsibility, nor any obligation whatsoever; and the fact that the Govern- ment may have formulated, furnished, or in any way supplied the said drawings, specifications, or other data is not to be regarded by implication or other- wise as in any manner licensing the holder or any other person or corporation, or conveying any rights or permission to manufacture, use or sell any patented invention that may in any way be related thereto.

2 I O WADC TECHNICAL REPORT 59-575 {y, Part n C NOX 263 773 OXIDATION OF TUNGSTEN AND TUNGSTEN BASED ALLOYS P. E. Blackburn K. F. Andrew E. A. Gulbransen F. A. Brassart Westinghouse Electric Corporation Research Laboratories JUNE 1061 Directorate of Materials & Processes Contract No. AF 33 (616)-5770 Project No. 7351 I AERONAUTICAL SYSTEMS DIVISION AIR FORCE SYSTEMS COMMAND UNITED STATES AIR FORCE WRIGHT-PATTERSON AIR FORCE BASE, OHIO NOTICES When Government drawings, specifications, or other data are used for any purpose other than in connection with a definitely related Government procurement operation, the United States Government thereby incurs no responsibility nor any obligation whatsoever.}

3 And the fact that the Government may have formulated, furnished, or in any way supplied the said drawings, specifications, or other data, is not to be regarded by implication or otherwise as in any manner licensing the holder or any other person or corporation, or conveying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related thereto. Qualified requesters may obtain copies of this report from the ARMED SERVICES Tech- nical INFORMATION agency , (ASTIA), arlington Hall Station, arlington 12, Virginia. This report has been released to the Office of TECHNICAL SERVICES , U. S.

4 Department of Commerce, Washington 25, D. C for sale to the general public. Copies of ASD TECHNICAL Reports and TECHNICAL Nutes should not be returned to the Aeronautical Systems Division unless return is required by security considerations, con tractual obligations, or notice on a specific document. FOREWORD This report was prepared by the Research Laboratories of Westinghouse Electric Corporation under USAF Contract No. AF ?3(6l6)-5770. The contract was initiated under Project No. 7351, "Metallic Materials", Task No. 73512, "Refractory Materials.*' The vork was administered under the direction of the Materials Central, Directorate of Advanced Systems Technology, Wright Air Development Division, with Lt.

5 W. E. Smith acting as project engineer. This report covers work conducted from August 1959 to December i960. The authors are indebted to Dr. R. J. Ruka for his help in x-ray diffraction techniques. We are also grateful to I. Spitzberg for his assistance in making the x-ray diffraction measurements and in determining the oxidation rates of tungsten at high temperatures. Pt. II ABSTRACT This paper describes the results of studies related to the oxidation of tungsten and its alloys. The pressure of WOo polymers over WO2 was measured in a tungsten Knudsen cell and found to agree with measurements in a platinum cell. Literature data for WOo and V.

6 'Oo were combined with vapor pressures determined in this project to give thermodynamic values for W1SO40, and W^O^S* Tungsten oxidation rates have been measured from 300 1'700 C and in pressures of oxygen between 2 x 10"! and 10 "^ atmospheres. The effects of oxygen pressure indicate that the rate may be governed by oxygen dissociating to atoms at the reacting surface. The oxidation rate is demonstrated to be independent of the oxide evapor- ation rate. All of the evidence indicates that if an oxide barrier layer is present at temperatures above 800 C it must be very thin. Studies on the oxidation of tantalum-tungsten alloys between 800 and 1200 C indicate that the 50-50 alloy has the greatest oxidation resistance, oxidizing at a rate as much as 10 times slower than tungsten alone.

7 PUBLICATION REVIEW This report has been reviewed and is approved. FOR TIIE COMMANDER J^> (J^l^JU^yx^^ll^ I. PERLMUTTER Chief, Physical Metallurgy Branch Meta]R and Ceramics Laboratory Directorate of Materials and Processes WADC TR 59-575 Pt. II ill TABLE CF CONTENTS Pace GENERAL INTRODUCTION 1 SECTION I. VAPOR PRESSURE I \ND TIE! I ICS OF TUNGSTEN OXIDES AND MIXED OXIDES OP TUNGSTEN 2 PRODUCTION 2 APPARATUS 3 SAMPLE MATERIAI 5 PROCEDURE 5 RESULTS , 6 1. Vapor Pressures over Tungsten Oxides 6 2. Thermodynamics 12 3. Tungsten Oxide Pressures over Mixed Oxides of Tungsten .. 16 DISCUSSION 10 SECTION II. KINETICS OP OXIDATION.)

8 19 INTRODUCTION 19 EXPERIMENTAL - MICROBALANCE SYSTEM 19 1. Microbalance , 19 2. Samples 19 RESULTS 21 1. Kinetic Study 21 A. Effect of Temperature 21 B. Effect of Pressure 25 2. X-ray Study 32 3. Metallographie Study 36 DISCUSSION - MICROBALAECE SYSTEM 36 EXPERIMENTAL - PRESSURE MEASURING SYSTEM kO RESULTS k8 1. Kinetic Study kQ A. Effect of Temperature k8 DISCUSSION - PRESSURE CHANGE METHOD 50 CTIOH III. OXIDATION OF TUNGSTEN AT HIGH TEMPERATURES 52 APPARATUS 52 SAMPLES 52 PROCEDURE 52 RESULTS .. 52 [OH IV. SUMMARY AND CONCLUSIONS 71 LIST OF REFERENCES 73 -575 iv LIST (ff ILLUSTRATIONS 1.)]

9 Induction Vacuum Furnace UI3CW3 . 2. W^OQ Pressure over W02 + W 51736U . 3. Logarithm of V/^0g Pressure over Tungsten Oxides at 1150 C .. 515726 . k. Tungsten Oxide Pressure over the W-Ta-0 and W-Hf-0 Systems . 515727 . 5. Photograph of Invar Balance M 19222. 6. Photographs of W and W-Ta Specimens BM 19218. 7. Evaporation of WO-, vs. Static Gas Pressure 5172^3 . 8. Effect of Temperature on Oxidation of 75W-25Ta Alloy, 900 - 1200 C 517137 9. Effect of Temperature on Oxidation of 90W-10Ta Alloy, 900 - 12C0 C .. 517135 10. Effect of Temperature on Oxidation of 50W-50Ta Alloy, 800 - 1200 C 51713^ 11.

10 Oxidation of W and W-Ta Alloys, 1200 C 517312 . 12. Effect of Pressure on Oxidation of W at 12O0 C, cm - cm 517138 . 13. Oxidation Rate vs. Oxygen Pressure 517363 Ik. X-Ray Diffraction Data of 9OW-10Ta Oxide vs. Standard Patterns EM 192MD. 15. X-Ray Diffraction Data of 75W-25Ta Oxide vs. Standard Patterns BM I923U. 16. X-Ray Diffraction Data of 5OW-50Ta Oxide vs. Standard Patterns BM 19239. 17. Photomicrographs of Metal-Oxide Interfaces, Pure W EM 19217. 18. Photomicrographs of Metal-Oxide Interfaces, 90W-10Ta and 75W-25Ta EM 19216. 19. Photomicrographs of Metal-Oxide Interfaces, 50W-50Ta.