General Electric Company

Brian Francis Mickle

Jon Conrad Schaeffer

Nripendra Nath Das

David Paul Mourer

Eric Scott Huron

Shesh Krishna Srivatsa

Kenneth Rees Bain

Jon Raymond Groh

Peter Wayte

Kevin G McAllister

Matthew S Tomaszewski

Ching-Ho Wang

A method of forming a component from a gamma-prime precipitation-strengthened nickel-base superalloy so that, following a supersolvus heat treatment the component characterized by a uniformly-sized grain microstructure. The method includes forming a billet having a sufficiently fine grain size to achieve superplasticity of the superalloy during a subsequent working step. The billet is then worked at a temperature below the gamma-prime solvus temperature of the superalloy so as to form a worked article, wherein the billet is worked so as to maintain strain rates above a lower strain rate limit to control average grain size and below an upper strain rate limit to avoid critical grain growth. Thereafter, the worked article is heat treated at a temperature above the gamma-prime solvus temperature of the superalloy for a duration sufficient to uniformly coarsen the grains of the worked article, after which the worked article is cooled at a rate sufficient to reprecipitate gamma-prime within the worked article.

Method of controlling final grain size in supersolvus heat treated nickel-base superalloys and articles formed thereby

A method for preventing clouding of a lens employed in a high-temperature oxidizing environment, an example of which is a lens of a pyrometer used to sense exhaust gas temperature (EGT) of a gas turbine engine. Clouding is prevented by inhibiting the generation of volatile oxide species that react with high-temperature lens materials, forming deposits including oxides of chromium, molybdenum and other elements having volatile oxide species. The method is particularly directed to a pyrometer whose lens is formed of sapphire (alumina) or silica, and is mounted within a structure formed of a material containing chromium and/or molybdenum, such as a superalloy or stainless steel. The method entails forming an alumina scale-forming barrier coating such as a diffusion aluminide on surfaces of the structure that are subject to oxidation and high temperatures. According to the invention, the alumina scale formed by the barrier coating inhibits the generation of other oxides at the coated surfaces, which would otherwise form volatile oxides that react with and form deposit on the lens. By inhibiting the formation of oxides other than alumina on surfaces surrounding the lens, lens clouding caused from volatile oxides is avoided. As a result, the optical performance of the lens is not degraded, and the precision of a pyrometer employing the lens to sense temperatures is maintained during operation of the engine.

Optical lens and method of preventing clouding thereof at high

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West Chester, OH, United States of America

Brian Francis Mickle