United Technologies Corporation

United States of America As Represented by the Secretary of the Air Force

Henry M Hodgens, Ii

Robert E Fishter

Kenneth C Long

William A Cellich

Hugh M Privett, Iii

The invention provides method and apparatus for chemical milling of a metal part in a milling solution that reduces hydrogen absorption by the part wherein, the metal part to be milled, which serves as the anode, and a cathode of more noble metal than the anode, are mounted in such solution. Unlike the prior art, the cathode and anode are separated in such solution but electrically connected by a conductor therebetween, which conductor is insulated from the milling solution. Thus anode and cathode are mounted, spaced apart in the milling solution, so that metal dissolves from the anode surface, milling such part while electrons flow from anode to cathode by said conductor so that hydrogen forms at the cathode, removed from the anode part, to reduce hydrogen absorption by such part. The anode part can be of, eg. titanium and the cathode of a more noble metal, eg. platinum, which serves to draw the hydrogen to the cathode and away from the anode part, preventing or reducing absorption of hydrogen into, eg. the titanium part and consequent hydrogen embrittlement thereof, which occurs in the prior art.

Method for reducing hydrogen absorption during chemical milling

A solution is described for the chemical processing of beta phase-containing titanium alloys. The solution contains HNO.sub.3 and HF, along with a small but effective amount of copper, ruthenium, rhodium, palladium, osmium, iridium, platinum or gold to reduce hydrogen absorption, ammonium formate and citric acid to increase the milling rate, and a surfactant to ensure a satisfactory milled surface.

Chemical milling solution for reduced hydrogen absorption

A solution is described for the chemical milling of niobium and niobium-base alloys. The solution contains about 25% HNO.sub.3, about 19% HF, balance H.sub.2 O, with additions of citric acid and ammonium formate to control the reaction rate and provide a smooth surface finish without intergranular attack, and a small amount of a noble metal to control hydrogen absorption. A process for using the solution to mill niobium alloys is also described.

Chemical milling of niobium

Electroless plating compositions are described which produce a boron containing nickel coating. The compositions comprise a water soluble nickel salt, a chelating agent, an alkali metal hydroxide, a boron containing reducing agent, and thiocarbanilide. The composition is particularly useful for providing such coatings on gas turbine engine parts and results in improved wear resistance.

Wear resistant electroless nickel-boron coating compositions

Electroless plating compositions are described which produce a boron containing nickel coating. The compositions comprise a water soluble nickel salt, a chelating agent, an alkali metal hydroxide, a boron containing reducing agent, and ethylenethiourea. The composition is particularly useful for providing such coatings on gas turbine engine parts and results in improved wear resistance.

Ethylenethiourea wear resistant electroless nickel-boron coating

A composition and method for removing deposits (10) from the internal components (24) of a gas turbine engine (18) utilizing a cleaning composition (15) which comprises an aqueous solution of hydroxylamine sulfate, a chelating agent, a compound selected from the group consisting of ammonium sulfamate, ammonium sulfamide, and hydroxylamine-o-sulfonic acid, and, an alkaline pH modifying substance added in an amount sufficient to achieve a pH value of between 6.5 and 14. The method involves contacting the deposits with the cleaning composition, such as in an apply and soak type pattern, chemically dislodging the deposits from the component surfaces. The engine is rinsed to remove the dislodged deposits and residual cleaning composition.

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Jupiter, FL, United States of America

Henry M Hodgens, Ii