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Double vacuum a r c remelted N i T i i n g o t s were vacuum i n d u c t i o n remelted and subsequently atomized u s i n g a high-pressure gas stream. Powders were c o l l e c t e d , loaded i n t o cans, and h o t i s o s t a t i c a l l y pressed (HIP1ed) .

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A technique used to predict constant amplitude crack growth in a surface flaw is presented. Various aspects of this technique that are discussed include: constant amplitude crack growth data, crack growth models, crack growth accumulation/ integration routine, surface flaw stress intensity factors, surface flaw transition to a through crack and the definition of failure/fracture of a specimen. The author's predictions and the results of a round-robin effort are discussed.

The effects of radiation damage with 1 to 3 keV x-rays on hydrogenated boron nitride films prepared by LPCVD have been investigated. It is shown that both the surface and bulk film properties of these materials are modified and may potentially limit the use of this material as a membrane in an x-ray mask structure. Specifically, it is shown that growths will form on exposed boron nitride surfaces irradiated in oxygen-containing ambients; optical transmission of irradiated films will degrade with the cumulative absorbed dose; the tensile stress of an x-ray mask membrane will decrease and introduce pattern distortions depending upon the irradiation dose/flux and exposure geometries. A model to evaluate the observed pattern distortions and a mechanism to explain the observed stress changes of the hydrogenated boron nitride films are proposed.