Abstract: A process for providing coatings on metal articles whereby the articles will be resistant to corrosion at elevated temperatures. The process involves the application of an overlay on an article surface, the overlay comprising a ductile metal of a composition normally resistant to corrosion at elevated temperatures. An outer layer of aluminide or metal which is resistant to corrosion at elevated temperatures but which is subject to embrittlement at such temperatures is applied to complete the coating. Porosity in the coating is then eliminated and a high integrity corrosion resistant coating not subject to cracking is obtained by heating the article in a gaseous atmosphere to elevated temperature and simultaneously applying isostatic pressure to the article.

Abstract: A method for consolidating powder metal preforms and for thereby producing high performance metal shapes from powder particles. The powder particles are consolidated into a shaped porous preform, and a coating is then applied to the resulting preform. The coating is initially porous whereby the coated preform can be degasified by subjecting the preform to a vacuum, particularly at elevated temperatures. The coated preform is then heated under vacuum to a temperature such that the coating is densified to the extent that it becomes non-porous. The coated preform is then subjected to a hot isostatic pressing operation whereby formation of a high integrity, fully dense metal shape results.

Abstract: A turbine nozzle has inner and outer shrouds structurally connected by hollow core members which together with nose and tail inserts retained in the shrouds form airfoil-shaped vanes. Openings in one of the shrouds supply cooling air to the hollow vane cores whose walls have orifices to impinge air upon the inserts. Spent air from the nose insert film cools the core. Air directed at the tail insert divides to flow through holes in the insert and to film cool the insert. Orifices and holes are cast or readily drilled into the parts prior to their assembly. For superior resistance to high temperatures, the inserts are preferably columnar-grained or monocrystalline superalloy castings which are brazed or welded into the shrouds and are replaceable to extend nozzle service life. Alternatively, ceramic or metal inserts are mechanically retained in the shrouds.

Abstract: A method for treating investment cast superalloy castings wherein the portions of the castings which solidify directly against the mold walls comprise a substantially continuous or encapsulating skin of a metallic and/or nonmetallic composition. In such castings, defects in the form of material voids, including defects present immediately beneath the skin, are eliminated by the application of heat and pressure. The castings are heated to temperatures sufficient to achieve metal movement in the form of yield or creep, and a pressure of at least about 10,000 psi is applied by means of a surrounding gaseous atmosphere. The heat and pressure application deforms the material in the area of the voids and consolidates this material to substantially remove the voids and to thereby improve the performance characteristics of the castings.