US2455804A - Nickel chromium tungsten composite metal body and method of making same - Google Patents

Description

' shown one of the various possible Patented Dec. 7, 1948 NICKEL CHBOMIIM TUNGSTEN COMPOSITE METAL BODY AND METHOD OF MAKING SAME Charles Eric Bansley, Sndbury, and Stanley Vaughan Williams, Kenton, England. assignors to The General Electric Company Limited,

London, England Application December 21, 1943, Serial In Great Britain January 1, 19 3 4 Claims. (CL 2 9191.2)

This invention relates to metal bodies and to their manufacture. Its primary object is to provide metal bodies well adapted to resist both chemical attack, for example oxidation and mechanical distortion when maintained at high temperatures, commonly called creep. Here and hereinafter the term metal includes alloys.

Certain base metals, particularly some alloys having nickel and chromium as main constituents, are very resistant to oxidation, but are subject to creep. Certain other metals, particularly tungsten, retain their mechanical strength at temperatures above that at which the first said metals creep rapidly or melt, but are easily oxidised. If the useful properties of both classes of metal could be combined in a single body, metal bodies more resistant to both creep and oxidation than any known base metal could be obtained. The object of this invention is to provide means for effecting such a combination.

According to the invention in its broadest aspect, a metal of the first said class is reinforced by a skeleton of a metal of the second said class,

in a manner similar to that in which concrete is reinforced by metal.

In some cases the reinforcement can be effected by forming a skeleton of the strong but oxidisable metal and casting the weak but chemically resistant metal round the skeleton. But it is necessary to prevent extensive solution of one metal in the other which might destroy both valuable properties. 'When one metal is tungsten and the other contains nickel this may be diflicult to avoid; for nickel and tungsten are mutually soluble. We have found that any deleterious mutual solution can be prevented by enclosing the skelton in the oxidation-resistant metal by the method of powder metallurgy.

According to the invention in a narrower aspect, the manufacture of a metal body comprises the steps (1) of forming a skeleton of a metal of the second said class, (2) of compressing round the skeleton the powder of a metal of the first said class or mixed powders of the components of a metal of the first said class, and (3) sintering the resulting product in such a manner that the particles of the powder or firmly united to each other and to the skeleton.

So long as the result is obtained. the sintering may be performed at a temperature below or at a temperature above that at which a liquid phase first appears.

In the accompanying drawings in which is embodiments of our invention,

Fig. l is a top phantom view of a metal body and made in accordance with our in.* vention; and

Fig. 2 is a sectional view therethrough taken substantially along the line 2-2 of Fig. 1.

In one method according to the invention, described by way of example, a skeleton it of tungsten wires is formed loosely woven together. Finely divided powders it, part of nickel and part of a chromium-rich (e. g. 50-50) nickelchromium alloy, are mixed in such proportions that the mixture contains 80% nickel and 20% chromium. The mixture is packed tightly round the skeleton, preferably by introducing it in small quantities and rammlngit. The whole body is then maintained at a temperature of 1200-1350 C. till the required union is attained. The period required for this purpose increases as the said temperature decreases; but even at the higher temperature is likely to be at least one hour.

We claim:

1. A composite metal body resistive to chemical attack and creep and essentially comprising an undissolved coherent skeleton of tungsten completely imbedded in a sintered powder mass essentially consisting of nickel and chromium.

2. A composite metal body resistive to chemical attack and creep, and essentially comprising an alloy containing substantially 80% nickel and 20% chromium reinforced by an undissolved, coherent, completely imbedded skeleton of tunasten wires woven together. I

3. A composite metal body resistive to chemical attack and creep and comprising an undissolved coherent skeleton of tungsten wires woven together and completely imbedded in a sintered mass of an alloy containing substantially nickel and 20% chromium.

4. The method of manufacturing a composite metal body resistive to chemical attack and creep.

said method comprising the steps of (1) forming a skeleton by weaving tungsten wires together, (2) compressing round said skeleton a powder composed of a mixture of nickel powder and a nickel chromium alloy powder in proportions such that the mixture contains substantially 80% nickel and 20% chromium, such compression being effected by introducing the mixture insmall quantities and ramming it, and (3) sintering the resulting product at a temperature between 1200 and 1350 C. until the particles of the powders are firmly united to each other and to said skeleton.

CHARLES ERIC RANSLEY.

STANLEY VAUGHAN WILLIAMS..

(References on following page) The following reterences are or record in the REFERENCES CITED file of this patent:

UNITED STATES PATENTS Number Name Date Zealen Apr. 26, 1921 Number 4 Name Date MacKenzie June 13, 1922 Coles July 21, 1931 Schwarzkopf Oct. 26, 1937 Hildabolt Dec. 30, 1941 Imes Mar. 24, 1942 Hack July 21, 1942 Schwarzkopf Mar. 27, 1945

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