| 摘要 |
A closed impeller 40 has a vane 61 with an inlet end 62 and an outlet end 64. The vane 61 has low 66 and high 68 pressure side surfaces with respective midpoints 74,122. A hard coating 100,101 is on both side surfaces 66,68. The hard coating 100,101 has a minimum coating thickness at the respective midpoints 74,122. The thin coating at the midpoints ranges from between about .085 and about 0.8 of either the maximum outlet coating thickness 104,126 at the outlet end 64 or the maximum inlet coating thickness 106,128 at the inlet end 62. The thickness profile of the coating 100,101, therefore, is thickest at the ends 62,64 and thinnest at the midpoints 74,122. The coating serves to provide greater protection to those parts of the blade 61 which in use undergo more stress. The coatings 100,101 may be formed by a monolayer of a nanocomposite, or a bonding layer of a selected material, or plasma enhanced magnetron sputtering (PEMS) or low temperature CVD. |
