Title

Refractory Coatings For Tungsten

Date

1961

Index Abstract

Contrails and DTIC condensed

Photo Quality

Complete

Report Number

WADD TR 60-825

Creator

Goetzel, C. G.

Landler, P.

Corporate Author

New York University, Research Division

Laboratory

Materials Central

Extent

51

Identifier

AD0258574

AD0258574

Access Rights

OTS

Distribution Classification

1

Contract

AF 33(616)-6868

DoD Project

7350

DoD Task

73500

DTIC Record Exists

Yes

Distribution Change Authority Correspondence

None

Date Modified

Scanned by request 5/18/2017 submitted by Honeywell Technology Library (Other Industry - Domestic)

Abstract

A preliminary study of the feasibility of protecting tungsten wires against oxidation at 3300°F (1815°C) was undertaken. A tungsten disilicide coat was the most promising coating for this temperature. Several siliconizing methods were given a cursory treatment, including vapor plating and dipping into molten copper-silicon bath, and the simplest, cementation, was selected for closer investigation. This operation was performed under flowing hydrogen atmosphere and such variables as temperature, time, and composition of the cementation pack were studied as a main part of our exploratory work. A single brittle tungsten-disilicide (WSi2) layer is formed by this method. The inherent brittleness of tungsten appears further aggravated by the development of micro-cracks in the layer as well as in the substrate during siliconizing. Oxidation tests using direct electrical resistance eating were performed. It was found that pack-siliconized wires can withstand oxidation at 3300°F in still air for prolonged periods up to and including 10 hrs. This is accomplished without any destruction of the coating in the high temperature zone owing to the formation of a viscous glassfilm on the surface. A pronounced tendency toward self-healing is a useful property of this type of coat. A serious drawback of the disilicide coat, however, is its low temperature oxidation ("Disilicide pest") which occurs in parts exposed at 1200° and 2280°F for prolonged periods. It causes a destruction of the disilicide layer over a period of 5 to 15 hrs, depending on coating thickness. It was the actual life determining factor in those tests where other failures caused by improper technique had been eliminated. Preliminary attempts to deposit ZrO2 on top of siliconized wires by means of plasma arc spray method remained largely unsuccessful because of poor adhesion. Where bonding was obtained, no improvement in life under high temperature oxidizing condition could be ascertained.

Report Availability

Full text available

Distribution Conflict

No

Date Issued

1961-03

Subject

Refractory Coatings

Tungsten

Antioxidants

Brittleness

Coatings

Diffusion

Flame Spraying

High Temperature

Oxidation

Oxides

Processing

Silicides

Silicon Coatings

Tungsten Compounds

Vapor Plating

Wire

Zirconium Compounds

Publisher

Wright-Patterson Air Force Base, OH : Wright Air Development Division, Air Research and Development Command, United States Air Force

Provenance

Lockheed Martin Missiles & Fire Control

Type

report

Format

1 online resource