US 5,057,340 AGranted

Method of forming a coating on a reactor coolant pump sealing surface

AssigneeWestinghouse Electric Corp.

InventorsNatraj C. Iyer, Eleanor Gettliffe

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Abstract

A ceramic-based coating is provided on a sealing surface of a sealing assembly component by processing and applying a powder mixture of ceramic particles and metal binder, encasing the coating of powder on the sealing surface by applying a metallic cover thereover, evacuating the atmosphere between the cover and coating, hot isostatic pressing the component and coating, cooling the component and coating, and after cooling thereof removing the cover from the coating. The powder processing includes mixing the ceramic particles and metal binder to produce a mixture, pretreating the mixture by heating it to the melting point of the metal binder which is less than the melting point of the ceramic particles to produce a mass of ceramic particles coated with molten metal binder and having a reduced gas content, cooling the mass of ceramic particles coated with molten metal binder to produce a solid mass thereof, and pulverizing the solid mass of metal binder coated-ceramic particles to granulate the powder mixture of ceramic particles to the desired size and still at least partially coated with metal binder. The resultant coating is densified substantially to its full theoretical density, metallurgically bonded to the substrate exterior surface, and has ceramic particles which are interparticle bonded together due to the processing step.

Claims18

Dependent claims

A method of forming a coating on a sealing surface of a sealing assembly component, said forming method comprising the steps of:

(a) processing a powder composed of a mixture of ceramic particles and a metal binder so as to substantially reduce the gas content of the mixture and at least partially coat the ceramic particles with the metal binder;
(b) applying the powder mixture onto a groove formed on the sealing surface of the sealing assembly component to form a coating thereon;
(c) encasing at least the coating on the sealing surface by applying a metallic cover thereover;
(d) evacuating the atmosphere between the cover and coating on the sealing surface;
and
(e) hot isostatic pressing the sealing assembly component and the coating thereon encased by the cover in a manner which densifies the coating to substantially its full theoretical density, metallurgically bonds the coating to the surface of the sealing assembly component at the groove thereon, and wets the ceramic particles with the metal binder and forms an interparticle bond between the ceramic particles wetted by the metal binder;
(f) said powder processing including
(i) mixing the ceramic particles and metal binder to produce a mixture thereof,
(ii) heating the mixture of ceramic particles and metal binder to the melting point of the metal binder which is less than the melting point of the ceramic particles to produce a mass of ceramic particles coated with molten metal binder and having a reduced gas content,
(iii) cooling the mass of ceramic particles coated with molten metal binder to produce a solid mass thereof, and
(iv) pulverizing the solid mass of metal binder coated-ceramic particles to granulate the powder mixture of ceramic particles to the desired size and still at least partially coated with metal binder.

8 more elements

A method of forming an annular coating on an annular sealing surface of a stainless steel sealing assembly component for use in a nuclear reactor coolant pump, said forming method comprising the steps of:

(a) processing a powder composed of a mixture of ceramic particles and a metal binder so as to substantially reduce the gas content of the mixture and at least partially coat the ceramic particles with the metal binder;
(b) applying the powder mixture onto a groove formed on the sealing surface of the sealing assembly component to form a coating thereon;
(c) encasing at least the coating on the sealing surface by applying a metallic cover thereover;
(d) evacuating the atmosphere between the cover and coating on the sealing surface;
(e) hot isostatic pressing the sealing assembly component and the coating thereon encased by the cover in a manner which densifies the coating to substantially its full theoretical density, metallurgically bonds the coating to the surface of the sealing assembly component at the groove thereon, and wets the ceramic particles with the metal binder and forms an interparticle bond between the ceramic particles wetted by the metal binder;
(f) said powder processing including
(i) mixing the ceramic particles and metal binder to produce a mixture thereof,
(ii) heating the mixture of ceramic particles and metal binder to the melting point of the metal binder which is less than the melting point of the ceramic particles to produce a mass of ceramic particles coated with molten metal binder and having a reduced gas content,
(iii) cooling the mass of ceramic particles coated with molten metal binder to produce a solid mass thereof, and
(iv) pulverizing the solid mass of metal binder coated-ceramic particles to granulate the powder mixture of ceramic particles to the desired size and still at least partially coated with metal binder.

7 more elements

Dependencies are inferred from the claim text.