CA1194893A

CA1194893A - Cemented carbide compositions

Info

Publication number: CA1194893A
Application number: CA000397737A
Authority: CA
Inventors: Thomas E. Hale; Roy C. Lueth; Warren C. Yohe
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1982-02-01
Filing date: 1982-03-05
Publication date: 1985-10-08
Also published as: AU7873181A; ZA818744B; JPS58110655A; ATE21939T1; AU553700B2; DE3272955D1; EP0085125B1; EP0085125A1

Abstract

ABSTRACT OF THE DISCLOSURE
Cemented carbide compositions useful for rock drilling and allied applications are described. These compositions comprise about 80 to about 97% by weight of refractory particles of, for example, tungsten carbide.
The particles are bonded within an alloy matrix of between about 5 and about 50% nickel, sufficient carbon to avoid the formation of detrimental carbon deficiency or excess carbon phases and a balance of about 95 to about 50% iron by weight. In a preferred embodiment, the alloy matrix additionally contains from about 5 to about 20% by weight of manganese.

Description

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~ ~'Jh~3 sackground of the Invention This invention is concerned ~7ith cemented compositions and, more particularly, ~"ith cemented carbide compositions having unique characteristics and physical properties particularly suited for drilllng and mining operations.
Similar compositions are well know for their combinations of hardness, compressive strength and abrasion resistance. secause of these properties, as ~ell as others, cemented carbide compositions are used extensively in industrial applications. Representative are cutting tools, drawing dies, wear parts, drills and other applications where hardness, compressive strength and abrasion resistance are of paramount importance.
A representative and wide variety of these compositions, different physical forms in which they may be utilized and means of production are described in U,S. Patent 3,38~,~65 of Humenik et al issued May 20, 1975 and U,S. Patent NO. 3,450,511 of Frehn, issued June 17, 1969.
These compositions are primarily composed or re~ractory ~articles of, for e~.ample, tungsten carbide bound within a metallic matri~,, Although cobalt is the most common rnetal for such matri~ binders, many others have also been ernplo~ed.
It i~ k~nown, for e~ample, that various advantages ma~ flow from the u.se of nickel and/or iron in these rnatxi~A binders. These metals have been substi-t1lted for sorne or all of the cobalt in selected compositions.
Such ~ub~itu-tions are, described in U.S, Patent No.
3-J 3,816,081 is~ued ~lune 11, 19'7~ to Hale; U.S. Patent No.
3,372,056 of (~uaa~ is~ued March 5, 1968 and U.S, Patent IZo . 3, 7~6"519 of Haxa et al. , issued ~ul~ 17, 1973.

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There, alloys containing both nickel and iron are di~clo3e-1 as being useful in ma'crix binders for tunysten and other such carbide particles.
An important quality of a cemented carbide compositions is its ability to resist the propagation of small cracks which form in the compositions surface.
It is of particular imprtance in, for example, a rock drill where such cracks may form soon after it is put into service. The resistance to propagation of surface cracks is referred to as fracture toughness or, in more exact terms, critical stress intensity parameter, i.e., KlC. This property is best measured in a test where a natural crack can be started and stopped several times, in such manner that the energy required to propagate the crack can be accurately determined.
Another quality of particular ;mportance is resistance to high applied stress; a circumstance again encountered in rock drilling. The involved property of hardness directly affects wear resistance and therefore the longevity of use of articles made from these cemented compositions.
Despite the wide spread use and i~vestigation of such cemented compositi,ons, substantial improvement in compositions useful in rock drilling has not been achie~Jed. ~Jhere increases in one such property have been obtained, other important ones often including abrasion resistance and hardness have suffered. Thus compositi,ons having the composite properties desired for thi,s purpose have remained unavailable.
Introduction to the Drawings F'igure 1 is a graph reflecting the surface hardening as a result of simulated rock dri],,Li,ng of t) ~ ,r) 2 4 of representative compositions of the prior art and present invention as a function of distance from the composition surface. Figure 2 is a graph of fracture toughness versus abrasion resistance for some compositions of this invention as compared to prior art cobalt tungsten carbide compositions.
Introduction to the Invention The present invention is directed to improved cemented compositions and, more particularl~, to cemented tungsten carbide compositions having particular utility for rock drilling and/or mining operations. These compositions solve many of the drawbacks of the prior art, including those already discussed above.
The present compositions are composed generally of from about 80 to about 97% by weight of refrac'cory particles of, for example, tungsten carbide. These particles are bound within from about 3 to about 20%
by weight of a metallic matrix comprising an alloy of between about 5 and about 50% nickel, sufficient carbon to avoid the formation of detrimental carbon deficient or excess carbon phases and a balance of from about 95 to about 50% i,ron by weight. In a further improved embodiment these alloys additionally contain manganese.
Description of the Invention The major component of the present cemented compositions is its refractory parti,cles. It is this component, generally present in about 80 to about 97%
hy total ~eight, which is primarily responsible for the abrasion resi~tance necessary for these composi-tions' utilities.
Tung3ten car'hide generall~ constitutes at ,1ea3t 50~, and prefera~Jly frvm 70 to lO0'~, of these refractory particles. Its well known ~,hysic,A1 Dro-perti-~make it particularly suitable for this purpose. In addition, various other materials may be employed in conjunction with it. For specific applications, par~icles of titanium carbide, tantalum carbide and/or various other known refractories may be admixed with the particles of tungsten carbide. Most commonly, these secondary refractories are utilized in an amount less than 50%, preferably less than 2Q%, by total weight of particles.
As known in the art, the carbide grain size may range widely. To provide the most desired combination of abrasion resistance and toughness, the carbide grain size may be from about one-half (1/2) to about 15 microns or mixtures thereof.
The matri~ binder for che refractory particles of the present invention is a metallic alloy. It is this alloy which is responsible for maintaining the physical integrity of the composition. secause of the unique properties of the present alloys, a superior combination of fracture toughness and abrasion resistance can be achieved as compared to many o those of the prior art.
The metallic alloy comprises and may consist esæentiall~ of from about 5 to about 50% by weight nic~el with the remainder or balance being from about '35 to about 50% by weight iron. Other metals such as cobalt molybdenum, copper, chromium and others may be present also. Within the foregoing proportions, such alloys pro~ide substantial improvement of, in particular the critical property of fracture toughness.

~ n addition to the foreyoing metallic componerltæ, the alloy should contain a sufficlent amount of r~ P 1~

carbon to avoid the formation of carbon de~icient phases.
Generally, no more than about 2~ carbon by allsy weignt will be present. An excess of carbon, sufficient to produce a C-2 or above rating per ASTM specification s-276 should be a-~oided also. Such an excess may reduce the desirable performance characteristic of the composition.
This carbon performs several functions in the alloy. More importantly, it may be utilized to avoid the formation of harmful double carbides of, for example, iron with the tungsten. Such double carbides are generally quite brittle and therefore also detract from important properties of the composition.
In a further embodiment of thepresent invention, the alloy of the binder matrix additionally contains manganese, desirably from about 5 to about 20% by weight.
This metal component has been discovered to be especially ad~Jantageous in the foregoing alloys where they contain about 5 to about 30~ by weight nickel.
The present cemented carbide compositions may be employed in any necessary shape and prepared by standard cemented carbide manufacturiny techniqueæ.
For con~Jenience, the separate alloy components (generally in finely powdered forrn) are first mixed together, for example in a ball mill. The admi~ture may then simply be presæed or molded into the desired shape. These steps are usually per~ormed in the presence of a lubricant such as para~fin or polyethylene glycol which can subse~uently be substantially remo~ed.
Once in lor simultaneous with formation of) the desired æhape, the molded components can be sintered by any ætandard carbide æintering technique known to one skilled in the art. Upon cooling, this yeilds an integral compact suita~le for initial uge, For those composites containiny manyanese, it is preferred to heat them in hydrogen or other reducing gas to the liquidus temperature of the binder and then complete the sintering in an inert or reducing gas.
This is done to keep the loss of manganese from the composition to a minimum.
Many of the unique and desirable properties of the present invention are believed to arise from a strain-induced partial transformation of the austenitic matrix alloy to martensite. This occurs under a variety of circumstances, including high applied stress. In the case of Hertzian contact (similar to that experienced by compacts in rock drilling) the surface layer will partially transform to martenize while the interior portion will remain austenite.
In accordance with the present invention, strain-induced transformation is believed to cause the present composition to exhibit a hardened surface, which enhances the wear resistance, while retaining a tough core of austenitic alloy matrix to resist breaking.
'rhe re~uisite cold working (or strain hardening) for the partial alloy transformation will take place under the conditions of use of the cemented carbide composi-tion in, for example, rock drilling.
The presence of manyanese in the subject alloys has an especially siynificant effect on this phenomenon. The rnanganese provides a highly desirable hardeniny transformation when the matrix binder is subjected to plastic defor~tion, such as that resul-ting from hiyh applied ~tress. ~Ihen hardeniny is localized ~ 3 ~ )2~

at the outer surface region of the composition, where the stress is applied. Consequently, the overall toughness of the product is maintained.
Description of the Drawings The in~ention of this application will be more fully described and better understood from the following examples and comparative results.

EXAMPLE

Various tungsten carbide sample compositions were prepared containing from 84 to 85%
by weight of tungsten carbide and 15 to 16%
by weight of binder matrix. These samples contained di~fering alloy constituents. Their physical properties were determined and were compared with the standard commercial grades of tungsten carbide -cobalt binder (~lC-Co.) as follow,s:

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~r)~P 1 Compositions X7503-86 and X7503-26A had relatively low nickel additions and relatively hiyh carbon additions. These cornpositions had a fracture toughness (KIc) which was inferior to that of comparable commercial grade WC-Co. i.e., Grade 55B and Grade 268.
Compositions X7503-86s, X7503-86E, X7503-86F
and X7503-86J, in which the nickel addition was from 30 to 40% and the carbon addition was 0.5%, showed a substantial increase in fracture toughness without significant decrease in abrasion resistance.
Compositions X7503-86G and X7503-86H, in which the nickel addition was in excess of 40% and the carbon was eliminated showed fracture toughness and abrasion resistance which were lower. Because abrasion resistance is equally as important as is fracture toughness to suitability of compositions for rock drilling, these compositions, even though equal or superior to commercial Grades 55B and 268 in fracture toughness, were inferior.

EXAMPLE II

Tungsten carbide sample compositions, all consisting of 88% by weight of tungsten carbide and 12% by weight of binder matri~ were prepared. Their phyæical properties were determined and were compared r~7ith designated standard commercial grades of ~C-Co compcsitions as follows:

C~J~S~ 1~J~

COMPOSITION ¦ BINDER MATRIX; ~BPASION F~AC~17UPE
p~EsIsrrA!~cE TOUGHNESS
DESIG21ATION _ l/i~OL. LOSS IC
Components HAP~IESS -1 r~~~-UNITS 7~OUNT wt percent ROC~LL A psi ~ in X7801-301 12~ 20%Ni; 10%Mn;
1.5% C;Fe* 85.7 5.5 17,000 X7800-302 12% 25%Ni; lo%Mni 1.5%Ci Fe* 85.5 4.3 18,000 Grade 231 10% 100% Co 87.7 3.6 15,000 Grade 55B 16% 100% Co 86.7 2.5 15,800 *balance All compositions of this invention showed significant improvement in abrasive resistance and fraction toughness. Thus the combination of properties exhibited b~ those compositions having iron/nickel/manganese/carbon alloy binders were particularly desirable are shown in Figure 2.

EXAMPLE III

A hardness profile was determined on inserts used for drilling rock for each of the following:

DE5IG~IATIOM BINDER MATPIX

AMOUNT COMPC~NENTS

X780()-302G 12% 25%Ni; 10%Mn; 1.5%C, balance Fe x7~Jo-3olAa 12% 20%Ni; 10%Mn; 1.5%Ci balance Fe Grade 231 10% 100% Co Grade 5$B 16% 100% Co Grade 241 10% 100% Co _ __ - ln -s,~ lr)~f~

These profiles were obtained hy Tukon Microharaness tester using a knoop indentor and a 500 gram load.
They are plotted as the graph of Figure 1.
As depicted in Figure 1, both samples of the present invention show bases for their substantial improvement over standard grades of cobalt-bound composi-tions. At the composition surfaces, samples X7800-302G
and X7800-301Aa exhibited the highest degree of work hardening. This localized surface superiority translated directly into improved wear resistance, particularly under high applied stress.
That surface superiority was combined with a rapid and substantial decrease in hardness with distance from the compositions surface. Thus, they also displayed higher degrees of localization of hardness superiority.
This in turn permits the retention of internal toughness.
Consequently, the compositions of the present invention exhibited relatively higher overall toughness than ones bound with a conventional cobalt matrix.
Figure 2 also shows the superiority of various of the present compositions. There the relative fracture touyhness and abrasion resistance for the sample and cornmer-cial compositions of ~xample II are depicted. It may be seen from EIG. 2 that the properties of the present compositions are superior to those of conventional tungsten carbide-cobalt ones.
Xt is to be understood that changes may be made in the foregoiny exemplary embodiments in the light of the above teachinys. Additional rnodifica-tions and/or 3() variations may also be made without depar-tiny from -the scope and spirit o~ the invention which therefore shall be rnea3llred by thf cla;rns wh:ich follow.

Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. In a cemented composite comprising refractory particles comprising tungsten carbide within a metallic matrix binder, the improvement wherein said matrix represents between 3 and 20% by weight of said composition and consists essentially of between 5 and 50% nickel, an amount of up to 20% carbon sufficient to avoid formation of detrimental carbon deficient or excess phases and the balance consisting essentially of iron.

2. The composition of claim 1, wherein the refractory particles additionally comprise titanium or tantalum carbide.

3. The composition of claim 2 wherein the composition has an austentic matrix which partially transforms to martensite at the surface under applied stress.

4. In a cemented composite comprising refractory particles comprising tungsten carbide within a metallic matrix binder, the improvement wherein said matrix represents between 3 and 20% by weight of said composition and consists essentially of about 5 to about 30% nickel, 5 to 20% manganese, an amount of up to 2% carbon sufficient to avoid formation of detrimental carbon deficient or excess phases and the balance consisting essentially of iron.

5. The composition of claim 4 wherein the refractory particles additionally comprise titanium or tantalum carbide.

6. The composition of claim 4 wherein the composition has an austenitic matrix core which partially transforms to martensite at the surface under applied stress.

7. In a process for drilling through rock with a cemented carbide tool, the improvement wherein said tool is composed of the cemented carbide composition of claim 1, 2 or 3.

8. In a process for drilling through rock with a cemented carbide tool, the improvement wherein said tool is composed of the cemented carbide composition of claim 4, 5 or 6.

9. A process for producing the composition of claim 1, 2 or 3 comprising:
(a) preparing a powdered admixture of the refractory particles and metallic alloy;
(b) subjecting said admixture to sufficient heat and pressure to produce an integral, sintered compact;
(c) cooling said compact; and (d) subjecting said compact to high applied stress to include formation of martensite in the surface layer of said composition.

10. A process for producing the composition of claim 4, 5 or 6 comprising:
(a) preparing a powdered admixture of the refractory particles and metallic alloy;
(b) subjecting said admixture to sufficient heat and pressure to produce an integral, sintered compact;
(c) cooling said compact; and (d) subjecting said compact to high applied stress to include formation of martensite in the surface layer of said composition.