GB792056A - Improvements in or relating to the production of powder metallurgy articles - Google Patents

Abstract

792,056. Powder metallurgy. BIRMING- HAM SMALL ARMS CO., Ltd. May 2, 1956 [May 31, 1955], No. 15499/55. Class 82(1) [Also in Group V] A method of producing ducted powder metallurgy articles e.g. turbine blades, comprises (a) supporting duct-forming elements 21 by and within the walls of a box B; (b) packing metal powder in the box to surround the elements; (c) introducing a liquid into the metal powder to occupy the spaces between the metal grains; (d) freezing the liquid to form a solid assembly of frozen liquid, metal powder and elements; (e) removing the assembly from the box and confining it in a die; (f) thawing the liquid and removing it; (g) compacting the assembly of powder and elements in the die by pressure applied transversely to the direction of length of the elements; and (h) removing the elements from (or dispersing them in) the compacted metal powder mass prior to, during, or after sintering of the compact, to form the ducts. The duct-forming elements 21 pass through holes 8 in the end walls 5 of the box and are secured to the said end walls, which are then moved apart by means of screws 19 to tension the elements. The liquid may be benzene, water, naphthalene or paradichlorobenzene, and may be removed by heat and/or a reduction of pressure. The packing of the box with powder may be assisted by vibrating the box. The elements may be copper wires, which are diffused into the compact on sintering; or cadmium or polystyrene, which are removed during sintering; or steel wires, which are removed mechanically or by dissolving out, after compaction but before sintering; or ceramic material which is removed after sintering. The metal powder may be stainless steel.