New glasses are used as protective coatings on metals and alloys susceptible to oxidation at high temperatures in oxidizing atmospheres. Glasses are stable and solid at temperatures up to 1000 deg C, adhere well to metal surfaces, and are usable for metals with broad range of expansion coefficients

Chapman, J. W.

Grekila, R. B.

Hirayama, C.

Mattox, D. M.

English

NASA Technical Reports Server

December 1970
	 Brief 70-10430 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
High Temperature Glass Coatings for Superalloys 
and Refractory Metals 
A series of high melting temperature glasses can 
be used as protective coatings on selected superalloys 
and refractory metals used in high temperature 
environments. Such metals and alloys are highly sus-
ceptible to oxidation at high temperatures in oxidizing 
atmospheres, and require surface protection. Re-
fractory metal surfaces have been coated with silicides, 
and superalloys with aluminides. Both coatings form a 
protective film by oxidizing in air and forming a thin, 
glassy, surface layer. Disadvantages of these coatings, 
however, are associated with the fact that the oxide 
surface layer becomes depleted and the silicon and 
aluminum diffuse into the substrate metal. Conven-
tional all-glass coating systems (metal silicates), though 
suitable for such applications, are not sufficiently 
viscous to be used on superalloys at temperatures 
above 800° to 900°C, and do not have sufficiently high 
melting points to be used for coating refractory metals 
at their normally high operating temperatures. 
The new glasses are stable and solid at temperatures 
up to 1000°C. They adhere well to the metal surfaces, 
and can be used for metals with a broad range of ex- 
pansion coefficients. In addition, the glasses are ther-
mally stable to approximately 1800°C without appreci-
able decomposition, and have sufficiently high vis-
cosities to protect the metals from oxidation at high 
temperatures and high gas velocities. 
The glasses may be easily crushed and powdered. 
The powdered glass can then be applied by conven-
tional methods or in vacuum atmosphere. For ex-
ample, the metal part may be heated in an induction 
furnace and the glass powder sprayed onto the hot sur-
face in an inert gas stream. To provide an acceptable 
coating, the glass powder must melt and flow to cover
the surface when brought in contact with the hot 
metal. 
Notes: 
1. The specific glass coatings used must be selected 
for compatability with the substrate metal and 
the environment to which the coated metal will be 
subjected. 
2. The following documentation may be obtained 
from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-CR-72520 (N70-14570), Development 
and Evaluation of Controlled Viscosity Coat-
ings for Superalloys 
Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B70-10430 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. Hirayama, J. W. Chapman, D. M. Mattox, 
and R. B. Grekila of 
Westinghouse Electric Corp. 
under contract to 
Lewis Research Center 
(LEW- 10700) 
Category 08 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned-rights.
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High temperature glass coatings for superalloys and refractory metals

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