ASTM F44

This specification covers requirements for powdered refractory metal coatings produced with or without additives. These coatings are applied to ceramic bodies in order to join ceramic bodies to metals or to other metallized ceramics by means of brazing or soldering. Included in this specification are requirements for a secondary metallic layer which is usually applied over the refractory metal layer. Two levels of quality for uniformity of metallizing are discussed, Level A and Level B. These levels discuss conditions and requirements needed in order to accept the uniformity of metallizing. Thickness of metallizing shall be measured using a metallurgical microscope. A polished cross-section that is perpendicular to the metallized surfaced is measured. The particles in the metallized layer must be sintered in order to form a dense matrix when viewed in cross section at 400 times. This cross section will indicate the extent of threedimensional sintering. A torque peel test and a tension test shall be performed in order to determine the bond strength of brazed metallized ceramics. Vacuum tightness of the brazed metallized ceramics shall also be determined.

This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

1. Scope

1.1 This specification covers requirements for powdered refractory metal coatings produced with or without additives. These coatings are applied to ceramic bodies in order to join ceramic bodies to metals or to other metallized ceramics by means of brazing or soldering. Included in this specification are requirements for a secondary metallic layer which is usually applied over the refractory metal layer.

1.2 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.

2. Referenced Documents

ASTM Standards
E3 Guide for Preparation of Metallographic Specimens
F19 Test Method for Tension and Vacuum Testing Metallized Ceramic Seals

Index Terms

bond strength; metallizing of ceramics; thickness control

Citing ASTM Standards

[Back to Top]