Densification of metal powder to produce cladding of valve interiors by

Abstract

A valve cladding method and associated system for implementation including the steps of preforming solid insert-members (22,24) of a vitreous material (having a rheological state that varys with temperature), to generally conform in shape to the cavity walls (12, 14) that are to be clad. The insert-member is fixtured (32) within the cavity to provide a generally concentric, annular space (28) of predetermined thickness and length between the insert-member and the adjacent walls to be clad, thereby defining an activation volume. This volume (28) is filled with loose metal powder (48) and vibrated to achieve tap density for a given powder blend. The activation volume is degassed, evacuated and sealed. The valve body (10') a thus loaded, is heated to a temperature at which the insert members becomes pliable, in the range from one-half to full melting temperature of the powder. Pressurization of the heated article is achieved by the use of a suitable press (50, 62) mechanical or hydraulic, with adequate configured, mated dies (52, 58). The heated valve body is placed within dies appropriate for applying a pressure-ramp-cycle to the pliable insert-members, sufficient for the insert to hydrodynamically transmit the applied pressure-pulse to the activation volume, whereby the metal powder is isodynamically compacted and metallurgically bonded to the adjacent cavity walls. After cooling in normalized fashion, the insert-member material reverts to its brittle, glass-like behavioral patterns that exist at room temperature and this reversion from pliable-to-brittle properties allows easy extraction of the insert-members.