GB923642A - Improvements in or relating to plain bearings, anti-friction elements or the like - Google Patents

Abstract

A plain bearing, e.g. a journal or thrust bearing or a slideway, comprises a metal matrix containing P.T.F.E. and a chemical compound which has, or which forms, with the metal or steel, a compound which has, a critical shear stress less than one-third of that of the matrix material at least at some point in the operating range. The compound for a 90:10 tin-bronze matrix may be potassium iodide, bromide or chloride. The compound may also be a salt with a base of ammonium, potassium, sodium, and lithium or may ionise in solutions or may have an ionic structure. It may be a halide, nitrate, nitrite, nitride, sulphate, sulphide, sulphite, carbonate, phosphate or acetate. The acetates or carbonates may react to give lamellar oxides. Potassium iodide will give iron iodide with a steel shaft and potassium carbonate will give iron oxide. Potassium bromide will give copper bromide with a bronze matrix. Sodium acetate, potassium nitrate or carbonate and lead chloride may be used with a bronze matrix. In an example 200 gms. of a 15% by wt. dispersion of P.T.F.E. in toluene and water with 1 gm. aluminium nitrate crystals is used to make a paste and 14,3 gms. of potassium iodide of 325 mesh are added. The matrix is then impregnated with the paste by heat and pressure. The disc is dried and the P.T.F.E. is sintered in nitrogen at 340 DEG C. A journal is made from 9:1 by wt. mixture of 100 mesh copper and 325 mesh tin and is sintered; P.T.F.E. and potassium nitrate are then incorporated by a vacuum process. A surface overlay of the P.T.F.E. and nitrate is then sprayed on and the bearing heated in nitrogen at 340 DEG C.ALSO:A plain bearing, e.g. a journal or thrust bearing or a slideway, comprises a metal matrix containing P.T.F.E. and a chemical compound which has, or which forms, with the metal or steel, a compound which has, a critical shear stress less than one-third of that of the matrix material at least at some point in the operating range. The compound for a 90 : 10 tin-bronze matrix may be potassium iodide, bromide or chloride. The compound may also be a salt with a base of ammonium, potassium, sodium and lithium or may ionize in solutions or may have an ionic structure. It may be a halide, nitrate, nitrite, nitride, sulphate, sulphide, sulphite, carbonate, phosphate or acetate. The acetates or carbonates may react to give lamellar oxides. Potassium iodide will give iron iodide with a steel shaft and potassium carbonate will give iron oxide. Potassium bromide will give copper bromide with a bronze matrix. Sodium acetate, potassium nitrate or carbonate and lead chloride may be used with a bronze matrix. To make a thrust plate, a steel disc is copper plated by electrolysis and a bronze powder of -100, +150 B.S. mesh is sintered thereon in a reducing atmosphere. 200 gms. of a 15% by wt. dispersion of P.T.F.E. in toluene and water with 1 gm. aluminium nitrate crystals is used to make a paste and 14.3 gms. of potassium iodide of 325 mesh are added. The matrix is then impregnated with the paste by heat and pressure. The disc is dried and the P.T.F.E. is sintered in nitrogen at 340 DEG C. A journal is made from 9 : 1 by wt. mixture of 100 mesh copper and 325 mesh tin and is sintered P.T.F.E. and potassium nitrate are then incorporated by a vacuum process. A surface overlay of the P.T.F.E. and nitrate is then sprayed on and the bearing heated in nitrogen at 340 DEG C.