| 摘要 |
The present invention is process for forming diffusion aluminide coatings on an uncoated surface (36, 38) of a substrate (42), without interdiffusing a sufficient amount of aluminum into a coating layer (44) to adversely affect the coating (44) growth potential and mechanical properties of said coating layer (44). A met al substrate (42) is provided comprising an external surface (36, 38) and an internal passage (34) therein defined by an internal surface (36), at least a portion of the external surface (38) of the substrate (42) being coated with a coating laye r (44) selected from the group consisting of .beta.-NiAl-base, MCrAlX, a line-of sight diffusion aluminide, a non-line-of sight diffusion aluminide, a pack diffusion aluminide, and a slurry diffusion aluminide on said substrate (42). The external surface (38) of the substrate (42) is cleaned. The metal substrate (42) is subjected to a alumin um vapor phase deposition process performed using a fluorine-containing activator selected from the group consisting of AlF3, CrF3, NH4F, and combinations thereof, at a rate in the range of about 0.036 mols of fluorine per ft3/hr of transport gas to abo ut 0.18 mols of fluorine per ft3/hr of transport gas, at a temperature in the range of about 1350.degree.F (730.degree.C) to about 1925.degree.F (1050.degree.C), using a transport gas selected from the group consisting of argon, nitrogen, hydrogen, and combinations thereof, the transport gas being provided at a flow rate in the range of about 20 ft3/hr to about 120 ft3/hr for a period of time in the range of about 2 hours to about 10 hours. The substrat e (42) is then cooled. The present invention is also a superalloy article (20) coated with a diffusion aluminide layer (40) using the diffusion aluminide coating process of the present invention. |
