Dimensionally controlled pack aluminiding of internal surfaces of a hollow article

A method for aluminiding an internal surface of an internal cavity, comprising the steps of

• providing an article having the internal cavity therein and an inlet to the internal cavity, and an outlet from the internal cavity having an outlet minimum transverse dimension of from about 0.0009 inch to about 0.012 inch;
• providing an aluminiding source powder having a minimum particle size greater than about 0.0015 inch and not greater than about 60 percent of the outlet minimum transverse dimension as a mixture of from about 5 to about 15 percent by weight of a metallic aluminum-containing powder and from about 85 to about 95 percent by weight of a ceramic powder;
• introducing the aluminiding source powder into the internal cavity through the inlet;
• heating the article with the aluminiding source powder in the internal cavity to cause aluminum to transport from the aluminiding source powder to the internal surface of the internal cavity, and for a sufficient time to produce an aluminide coating on the internal surface having a thickness of less than about 0.002 inch;
• and thereafter
• removing the aluminiding source powder from the internal cavity through the inlet.

A method for aluminiding an internal surface of an internal cavity, comprising the steps of

• providing a hollow gas turbine blade having the internal cavity therein, wherein the internal cavity includes
• an inlet having an inlet minimum transverse dimension, and
• a set of trailing edge cooling outlets, each trailing edge cooling outlet having an outlet minimum transverse dimension smaller than the inlet minimum transverse dimension, wherein the outlet minimum transverse dimension is from about 0.009 inch to about 0.012 inch;
• providing an aluminiding source powder having a minimum particle size of greater than about 0.0015 inch and not greater than about 0.005 inch, and wherein the aluminiding source powder comprises a mixture of from about 5 to about 15 percent by weight of a metallic aluminum-containing powder and from about 85 to about 95 percent by weight of a ceramic powder, to deposit an aluminum-containing coating on the internal surface of the internal cavity;
• introducing the aluminiding source powder into the internal cavity through the inlet;
• heating the article to a temperature of from about 1750° F. to about 2000° F., and for a time of from about 2 hours to about 12 hours;
• and thereafter
• removing the aluminiding source powder from the internal cavity through the inlet.