US2711009A - Corrosion resistant sintered stock containing mixed carbides - Google Patents

Description

United States Patent CORROSION RESISTANT SINTERED STOCK CONTAINING MIXED CARBIDES John C. Redmond, Greensburg, and John W. Graham, Ligonier, Pa., assignors to Kenname'tal Inc., Latrobe, Pa., a corporation of Pennsylvania No Drawing. Application October 8, 1952, Serial No. 313,810

3 Claims. (Cl. 29-182.7)

Our invention relates to an improved corrosion-resistant hard composition of matter and has to do, more particularly, with improvements in the corrosion-resistant hard composition of matter described and claimed in the pending application for United States Letters Patent of Philip M. McKenna, Alex G. McKenna and John C. Redmond, Serial No. 268,004, filed January 24, 1952, as a continuation-in-part of an earlier application, Serial No. 74,742,

filed February 5, 1949, now abandoned.

The principal object of our invention is to provide a sintered hard composition of matter which, with the density, hardness and resistance to oxidation of the composition of said application, will have a greater transverse rupture strength at room temperature.

A primary method of evaluation of compositions, such as those disclosed in said application, has been evolved and is called the stress-rupture test. It consists of maintaining a static tensile load on a suitable specimen at some specified elevated temperature until the specimen fails by breaking in tension in some interval of time between one and 1000 hours. By testing a series of specimens at various loads and at one temperature a graph can be drawn with time the abscissa and stress as the ordinate. When scaled properly a straight line results. The tests are generally made at several temperatures to develop a range of stress-temperature conditions. Various alloys or compositions are compared by comparing the slopes of the lines on the several graphs. A further object of our invention is to provide a sintered hard composition of matter which gives better results under the stress-rupture test.

A further object of our invention is to provide a sintered'hard composition of matter having increased tensile strength and an increased modulus of elasticity.

Further objects, and objects relating to details and economies of operation, will appear more definitely from the detailed description to follow.

In general, our invention consists in substituting, for

constitute from 20% to 50% of the composition, and the molybdenum should constitute from 5% to 25% of the said alloy,

The following are specific examples of compositions made in accordance with our invention.

Example I This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium,

tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

2,711,009 Patented June 21, 1955 The titanium carbide used, in this and the following examples, was substantially devoid of free titanium, free carbon, oxides and nitrides, and prepared by the method described and claimed in United States Letters Patent of Philip M. McKenna, No. 2,515,463, patented Iuly'18, 1950. The Cb(TaTi)C used in this end and the following examples contained about 45% columbium carbide (CbC), about 42.5% tantalum carbide (TaC) and about 12.5% titanium carbide (TiC) and was made in accordance with United States Letters Patent of Philip M. McKenna, No. 2,124,509, patented July 19, 1938. The proportion of the ingredients of Cb(TaTi)C, given above, are not critical and may vary somewhat depending on the columbite ore used to make it.

The hard composition of matter made from the mix above specified, by the procedure hereafter described, had a density of 6.06 grams per cubic centimeter, a hardness of 88.7 on the Rockwell A scale, and a transverse rupture strength at room temperature of 191,000 p. s. i. (pounds per square inch). Tests of a number of specimens of this composition showed an average tensile strength of 119,300 p. s. i. (pounds per square inch) and an average Youngs modulus of elasticity between zero and maximum stress of 57.6 10 p. s. i. These values were considerably higher than those for a composition that was identical except that it contained no molybdenum and 30% nickel. Specimens of the composition of Example I gave better results under the stress-rupture tests referred to above. This composition proved to be extremely resistant to corrosion or oxidation at high temperatures.

Example II This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent .TiC 57.0 Cb(TaTi)C 8.0 Ni 30.0 Mo 5.0

Example 111 This composition consists of titanium carbide (TiC), acomplex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 62.0 Cb(TaTi)C 8.0 Ni 28.5 Mo 1.5

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 6.05 grams per cubic centimeter, a hardness of 86.9 on the Rockwell A scale, and a transverse rupture strength at room temperature of 155,000 p. s. i.

This composition proved to be extremely resistant to corrosion or oxidation at high temperatures.

Example IV This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 62.0 Cb(TaTi)C 8.0 Ni 22.5 Mo 7.5

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 6.02 grams per cubic centimeter, a hardness of 90.0 on the Rockwell A scale, and a transverse rupture strength at room temperature of 173,750 p. s. i. Specimens of this composition gave improved results under the stress-rupture tests above mentioned and this composition proved to be extremely resistant to corrosion or oxidation at high temperatures.

Example V This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 72.0 Cb(TaTi)C 8.0 Ni 16.7 Mo 3.3

Example VI This composition consisted of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 72.0 Cb(TaTi)C 8.0 Ni 15.0 Mo 5.0

The hard composition of matter made from the mix above specified, by the procedure hereinafter described,

and a density of 5.75 grams per cubic centimeter, a hardness of 91.8 on the Rockwell A scale, and a transverse rupture strength at room temperature of 152,800 p. s. i. (pounds per square inch). Specimens of this composition gave improved results under the stress-rupture tests referred to above and the composition proved to be extremely resistant to corrosion or oxidation at high temperatures.

Example VII This composition consists of titanium carbide (TiC),

a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as 4 Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 55.0 Cb(TaTi)C 15.0 Ni 27.0 Mo 3.0

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 6.30 grams per cubic centimeter, a hardness of 87.0 on the Rockwell A scale, and a transverse rupture strength at room temperature of 172,000 p. s. i. (pounds per square inch). Specimens of this composition proved to be extremely resistant to corrosion or oxidation at high temperatures.

Example VIII This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 55.0 Cb(TaTi)C 15.0 Ni 28.5 Mo 1.5

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 6.22 grams per cubic centimeter, a hardness of 86.3 on the Rockwell A scale, and a transverse rupture strength at room temperature of 150,000 p. s. i. (pounds per square inch). This composition proved to be extremely resistant to corrosion or oxidation at high temperatures.

Example IX This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 56.0 Cb(TaTi)C 4.0 Ni 30.0 Mo 10.0

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 6.24 grams per cubic centimeter, a hardness of 87.5 on the Rockwell A scale, and a transverse rupture strength at room temperature of 216,000 p. s. i. (pounds per square inch). Specimens of this composition proved to be resistant to corrosion or oxidation at high temperatures although not so resistant as the compositions previously described.

Example X This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 66.0 Cb (TaTi) C 4.0 Ni 28.5 Mo 1.5

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 5.92 grams per cubic centimeter, a hard- *5 ness of"85f.9 on the Rockwell Arscak, 'and 'a transverse rupture strength of 206,000 p. "s. 'i. '(pounds per square im'rhi) The resistance to corrosion or oxidation at high temperatures of this "composition is good, although not quiteas good as that of the compositions ofExampl'e's I to VIII, 'inclu'sive.

Example 5&1

This composition .consists o'fltitanium carbide I(TiC), aco'mplex carbide .solid. solution containing cdlumbium, tantalum, titanium-and caibon and referred to herein-as Cb(TaTi)C, nickel and molybdenum, in the"'following proportions, by weight;

.Per cent The hard composition of matter made from the above specified, by the procedure .herein'a'fter described, hadadensityfof 5.82 gramsper cubic centimeter, aihardness "of 87 .2 "on the Rockwell A scale, and "a transverse rupture strength at .room temperature .of *16'95500 p.1s. i.

(pounds per :square inch) The resistance .of specimens dftliis composition to corrosion or oxidation at hightem- "p'eratures was .found to be good 'as compared with the compositions cfJExampIes I' to VII, inclusive, which were "classified as very, good,

:nxam 'le XII ilihis' composition consists of titanium :carbide (l-TiC), a complex carbide =solid isolut'ion containing Icolum'bium,

tautalum, titatitumrand carbonand :referredito herein as .bz(TaIii.)'C,.1nickel and "molybdenum, :in the '1 following :propottionsgbywweight:

' Per cent Fi'C ""6 60 Cb(T3Ti-)C c L 4:0

ferred to above. This composition proved to have a resis'tance -to corrosion-or oxidation "at high temperatures *tnat wasclassified'as-good'as 'compared withthte resist- "fiance to corrosion and -oxidationo'f"'Examples I to 'VIII, in'clusivepwliich -was-characterized as very good.

Example XIII This composition consists of titanium carbide (TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred to herein as Cb (TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Per cent TiC 42.0 Cb(TaTi)C 8.0 Ni 40.0 Mo 10.0

The hard composition of matter made from the mix above specified, by the procedure hereinafter described, had a density of 6.80 grams per cubic centimeter, a hardness of 83.6 on the Rockwell A scale, and a transverse rupture strength at room temperature of 202,000 p. s. i. (pounds per square inch). The resistance to corrosion or oxidation at high temperatures of specimens of this composition, however, "were characterized good to poor.

Example XIV This composition consists of titanium carbide -(TiC), a complex carbide solid solution containing columbium, tantalum, titanium and carbon and referred-tobereinzas Cb(TaTi)C, nickel and molybdenum, in the following proportions, by weight:

Percent TiC 52=0 Cb(TaTi)C -2 8.0 'Ni. .2510 .Mo -n. 4.510

The hard composition of matter made from the :mix above specified, by the ,procedure hereinafter described, had a density of 6.56 -per cubic centimeter, -a hardness of 89.6'on the :RockwellAscale, and-.aitransverse rupture strength at room temperature of .175 ,5.00,p. s. i. (pounds per square inch). However, the resistanceito @corrosion or oxidation at high temperatures of specimens ;of this composition was 'found'to be zpoor.

The .compositions of matter above described may 'be made by the method usually :used rfor making cemented car bide tool :compositionsiexcept that certain refinements are desirable for producing the best :results. :carbide constituents of the composition, 'in Ithe form :of :crystals passing through a sieve having .110!) -meshes rtO athe inch, and the powdered *or rauxiliary :metal (nickel and molybdenum), having an average-.particlesize of about 25 microns, arezchargedtintoarsteel-ballmill. The halls used in the mill may be eithercementedcarbide (or :steel, since the presence of iron in these 'zeoinpositions zis mot deleterious. The ball mill is then .filled with ,a light petroleum solvent to exclude the air therefrom and is :thereupon sealed, and ,the'chargeis ball-milledifor from three to 'six'days, tat the end of'which time the liquidin the mill and charge is removed hy decantation andrevaporation and a temporary binder, sucl1=as 0t25=to 11.00% of parafiin, is incorporated with the material. The average Jparticle size of the material, ;at the end of ;the 'ball milling operation, is from 1*to '5 microns. l the-(mixture is/next pressed to theidesired shape, .or as near to -it as feasible. Although this maybexdone by anyconventionalzpressing method, we have :foundtthat much more:de'sir-able results vare obtained by the useiof tthe -.-explosive pressing process, described [and claimed tin the spending :application for .United States-Letters 'Patent of Philip M. -McKenna, John =C. Redmond and Emlyn N. :Smith, Serial:No. 166,510,

filed August 6, 1947, entitled Explosive Pressing of Rowtiered Compositions, rupon-rwhich U. .S. leettersrli'atent No. 2,648,125 were :granted 1onsAugust :11, 1953. .Accord- Sing -.to this :process ZPI'ESSUI'CfiS applied rtouthe materialihydrostatically and rapidly from all directions and very high pressures may be so applied. After pressing the mixture to the desired form, the pieces may thereupon be sintered, or they may be further shaped by machining operations and, then, sintered. However, if any very complex shape is required, the material in this form has insufiicient strength to withstand the necessary machining operations and, in that case, it is given a preliminary heat treatment at temperatures of from 1900 to 2100 F. to give it sufficient strength to withstand the pressure of machining or working with diamond tools, but such heat treatment is as may be required, by grinding with a diamond wheel.

The sintering temperatures used in producing the compositions of Examples I to XIV, inclusive, are as shown by the following tabulation:

It is our belief that at the sintering temperatures employed the nickel and molybdenum alloy so that the metal binding the carbide particles of the composition together is an alloy of nickel and molybdenum. The remaining metals of the iron group, that is, cobalt and iron, are

equivalents of nickel for use in the making of these hard compositions of matter and cobalt or iron may be substituted for the nickel in the above compositions.

To determine the resistance of the compositions to oxidation and corrosion at high temperatures oxidation tests at 1800" F. were made on the specimens in eleven eighteen-hour increments for a total time of 198 hours. Those compositions which withstood the complete test of 198 hours with no more than .003 inch of adherent oxide growth per face were classified as excellent. Such compositions usually oxidized in a decreasing parabolic rate indicative of self protection and long life under severe oxidizing conditions. Those compositions which have the decreasing parabolic rate type of oxidation resistance or a slow linear rate and in which an inherent oxide coating forms that is greater than .003 inch and less than .008 inch in 198 hours are classified as good with respect to resistance to oxidation or corrosion at high temperatures. Those compositions which oxidize to a greater extent than .010 inch per face under the conditions specified above, or which develop a loose, flaky or powdery coating but which do not lose shape in 198 hours are classified as poor with respect to resistance to oxidation or corrosion at high temperatures.

From the foregoing examples it will be seen that compositions containing from 42 to 72% T iC, from 4 to 15% Cb(TaTi)C and from 20 to 50% of a binder metal alloy of nickel and molybdenum in which the molybdenum constitutes from 5 to 25 of the alloy have very desirable characteristics. The most desirable characteristics appear to be those of compositions including from 55 to 72% Tic, from 8 to Cb(TaTi)C and from to 35% of a binder metal alloy of nickel and molybdenum in which the molybdenum constitutes from 5 to of the alloy.

We are aware that the compositions of matter herein described are susceptible of considerable variation from the specific proportions shown without departing from the spirit of our invention and, therefore, we claim our invention broadly as indicated by the appended claims.

Having thus described our invention, what we claim as new and useful, and desire to secure by United States Letters Patent, is:

1. A corrosion-resistant sintered hard composition of matter consisting of from 42% to 72% titanium carbide (TiC), substantially devoid of free titanium, free carbon, oxides and nitrides, from 4% to 15% of a complex carbide solid solution containing columbium, tantalum, titanium and carbon, and from 20% to of a binder metal alloy of nickel and molybdenum, in which the molybdenum constitutes from 5% to 25% of the alloy, said composition being characterized by a density of from 5.6 to 6.8 grams per cubic centimeter, a hardness on the Rockwell A scale exceeding 83.5, a transverse rupture strength, at room temperature, greater than 150,000 p. s. i. (pounds per square inch), and high resistance to oxidation at temperatures of 1800" F. and above.

2. A corrosion-resistant sintered hard composition of matter consisting of from to 72% titanium carbide (TiC), substantially devoid of free titanium, free carbon, oxides and nitrides, from 8% to 15% of a complex carbide solid solution containing columbium, tantalum, titanium and carbon, and from 20% to 35% of a binder metal alloy of nickel and molybdenum, in which the molybdenum constitutes from 5% to 25 of the alloy, said composition being characterized by a density of from 5.6 to 6.3 grams per cubic centimeter, a hardness on the Rockwell A scale exceeding 86, a transverse rupture strength, at room temperature, greater than 150,000 pounds per square inch, and high resistance to oxidation at temperatures of 1800" F. and above. I

3. A corrosion-resistant hard composition of matter consisting of about 62% titanium carbide (TiC), substantially devoid of free titanium, free carbon, oxides and nitrides, about 8% of a complex carbide solid solution containing columbium, tantalum, titanium and carbon, and about 30% of a binder metal alloy of nickel and molybdenum, in which the molybdenum constitutes about 15 of the alloy, characterized by a density of about 6 grams per cubic centimeter, a hardness on the Rockwell A scale of about 88.7, a transverse rupture strength at room temperature, of about 191,000 p. s. i., and high resistance to oxidation at temperatures of 1800 F. and above.

References Cited in the file ofthis patent UNITED STATES PATENTS 2,023,413 Fetkenheuer Dec. 10, 1935 2,106,162 Balke Jan. 25, 1938 2,124,509 McKenna July 19, 1938 2,147,329 Willey Feb. 14, 1939