In a ceramic part having at least one small hole or both a hollow portion and small hole(s) which extends from the hollow portion to an outside, an edge portion of the small hole(s) is beveled. In a ceramic part having at least one small hole for a cooling mechanism through which a cooling medium is circulated, the surface roughness of an inner surface of the small hole is R.sub.max 7 .mu.m or below. Such a ceramic part having at least one small hole has no chipping or edge around the small hole(s) which can cause breakage at high temperatures and under high pressures, and is thus stronger than a conventional ceramic part. Such a ceramic part is suitable for use at a high temperature, for example, at 1000.degree. C. or above, and is particularly suitable as a gas turbine member, such as a turbine blade or a turbine nozzle of a gas turbine.
This application is a continuing application of U.S. Ser. No. 08/269,626, filed Jul. 1, 1994, now allowed, which in turn is a continuing application of U.S. Ser. No. 08/035,803, filed Mar. 23, 1993 now abandoned.
Priority Data
Mar 25, 1992 [JP] 4-67649 Mar 30, 1992 [JP] 4-73853
A method is disclosed for reducing the variance in the coolant consumption of components of a turbo-machine, in particular a gas turbine. The components are provided with one or more holes for the passage of a coolant, wherein a surface roughness existing inside the holes is reduced by mechanical finishing. The method is characterized by mechanical finishing that is performed by reshaping rough points that cause the surface roughness using a cold working process such as at least one of beating, pressing and rolling. The method permits a simple reduction of the surface roughness without creating finishing residues that could result in obstructions of the holes.
