US2074847A - Hard alloy - Google Patents

Description

uNiTEosr-A res" r 2,014, 41 a HARD LOY V Louis Edmond Lemaigre, Paris, France, assignor, to General Electric Companyzxa corporation of New York No Drawing. Application August 4, 1934, Serial No. 738,537. In France August 19, 1933 1.Claim., (cits-136) Experience has proved that the extra-rapid cutting of various steelsgparticrilarly very mild steels, cannot be accomplished as cheaply as pos- 'which are""sintered together with alloys of the sibly when the cutting tool employed is a sintered alloy consisting oitungstencarbide with cobalt or another ferrous metal. On the other'hand, if weight by weight of small percentages of ti'ta-' nium carbide TiC issubstituted for the tungsten carbides WC andwzq'for instance, to'30%, cutting tools are obtained which are much harder and which can hold the highest industrial "speeds now used inthe working of steel. Ternary alloys of tungsten carbides. of titanium carbide and cobalt or, another metal of the, same group have already been described.

.It is also known that the tungsten carbides st'ellite type, sucfiyas lcob alt, tungsten, withthe l provisional Patent No, 339,540 of the applicant, for which an application was filed on September castings are chilled or otherwise.

optional presence of molybdenum, chromium, vanadium. manganesaf iron and carbon, have made it possible to make particularly tough,

and very hard tools which are suitable for. the working of castings regardless of whether "the However, up to the present, the advantages, due to the sintering of the mixtures of tungsten carbides WC, W2C and titanium carbide TiC with a metallic binder having a cobalt base, a tungsten base or other metal bases (the latter being optional) have been ignored. Such alloys have been described in the 5, 1932, and which is now. French Patent 756,523,

delivre September 25, 1933 and inthe patent of addition whose provisional number, is 31,372 for which an application was filed on November 25, 1932; now French additional Patent 43,192,

.delivre December 27, 1933 but these patents dealt with binders which could be hardened by means of a suitable heat treatment.

According to the present invention, the hard tungsten, carbides and titanium carbides are sintered with hard, tough alloys. whose structural hardness is attained by virtue of their chemical composition and preparation, said hardness being independent of any additional heat treatment. These new alloys have among others the following characteristics:

(1)' They permit the extra rapid machining of steels of any degree of hardness.

(2) Their toughness, whichexceeds that of the alloys known heretofore, renders them suitable for the working of cast parts which have been improperly treated and whose hardness, which.

is altogether irregular throughout the parts, sometimes causes the breaking or the premature loss of the cutting edge in the case of the tools known heretofore. 1

In order to set forth clearly the invention, a few examples will be described.

' mixing.

Example 1. :Ihe' alloy may consist of the 'iollowing ingredients:-i-, .1

, H Percent Titanium carbidegn; 8 Tungstencarbideul L .80 Tungsten 6 .Cobalt 6 ,Thetungsten carbides consist of a mixture of CW and'CWz, whose total carbon content may range between 5-and 6.1%. -All the finely powdered constituents aremixed intimately in such a way as to obtain a frictional efiect during the This can be brought about by the use of a ball mill. taken to prevent oxidation of some of the constituents which are mostlikely to undergo However, precautions should be:

changes, particularly tungsten and the carbide v W2C. After mixing, the uniform and homogeneous powder thus obtained is subjected to'aload of 2 to 10 tons per sq. cm. The parts thus'o'b tained arehardened by a heat treatment in a non-oxidizing atmosphere which may be neutral or-reducing or a vacuum. The maximum temperature employed ranges from about 1500 to 1800 degrees C., the desired temperature level being held for 10 to 300 minutes, depending upon the hardness required. If desired, a first sintering at, a lower temperature, for instance below 1200 degrees C. may be employed, in order that the parts may not attain their final hardness immediately, and so as to permit a certain rough complex alloy consisting substantially of metal of the iron group and metal of the sixth group of Mendelejefis periodic table of elements, for instance, iron-cobalt-tungsten in the weight proportions of 2, 4 and 6; or also cobalt-tungstenchromium (for instance 6 t 5 1); or cobaltmolybdenum-tungsten-chromium (for instance 6 2 1 5 0.5); cobalt-tungsten-iron-vanadium "(for instance 4 6 2 0.3) etc. In all these cases,

the hardness and the duration of the final sintering are so regulated as to make the structure of the auxiliary alloy perfectly homogeneous.

Example 3.-The total carburization of the titanium involves some dimculties; most frequently one obtains a mixture (or perhaps a solid solution) of the carbide TiC with a variable proportion of the nitride TiN. However, experience has proved that one can use, without trouble, these more complex products, provided'the nitride 6 content remains rather low, for instance, less than 20 per cent of the total weight of titanium carbide plus titanium nitride. Good results have been also obtained with the formula of Example 1,

in which the carbide T10 is replaced partly by l0 TiN containing 1.1% nitrogen.

Example 4.-It is also possible to manufacture Y the various alloys that are the subject of the invention by means of a sintering which may take place under simultaneous or alternate temperal6 ture and pressure effects, for instance, between 1350 and 1800 degrees C. at 50 to 200 kg./sq. cm.

in the case of Example 1.

These various alloys'hereinbefore disclosed are tough, the more so the lower the nitride content 20 of the titanium carbide, and they permit work- Roughing:

Feed per revolution ..mm 1.5 Cutting depth .mm 2 Speed per minute in meters--- 40 3 Finishing: 2

Feed per revolution mm 0.1 Cutting depth mm- 0.5 Speed per minute in meters 250 40 It is obvious that the alloys 'which have been described in the foregoing are only given by way of examples and that they in no wise limit the scope of the invention. In general, the present invention covers alloys consisting substantially of titanium carbide TiC, tungsten carbide WC and a binding alloy with or without tungsten carbide W2C and titanium nitride TiN. The binding alloy. of which the alloy Co+W in substantially equal weights constitutes the simplest type is hard in itself without heat treatment. The respective proportions by weight of the extra hard constituents (carbides and nitride) on the one hand and of auxiliary alloy on the other hand may vary between about 97 and about 78 in the case of the first constituents and between about 3 and about 22% in the case of the auxiliary alloy.

' Experience has proved that these alloys may likewise be prepared by fusion and casting, or also by impregnation of the extra-hard, sintered constituents by means of the auxiliary alloy whichis brought to the liquid state at a high temperature.

What I claim as new and desire to secure by Letters Patent of the United States, is:--

A sintered compositionconsisting substantially of tungsten carbide, titanium carbide, titanium nitride, and a binder alloy for said carbides and nitride, said binder alloy consisting substantially of metal, of the iron group and metal of the 6th group of Mendelejefis periodic table of elements and comprising about 3% to 22% by weight of I said composition, the weight of the tungsten carbide being about ten times the combined weight of the titanium carbide and titanium nitride, and the weight of the titanium nitride being an appreciable amount but less than 20% of the combined weight of the titanium carbide and titanium nitride;

LOUIS EDMOND LEMAIGRE.