IL35674A - Nickel-molybdenum bonded titanium nitride-titanium carbide compositions - Google Patents

Description

BONDED TITANIUM TITANIUM CARBIDE PONT DE AND COMPANY Background of the Invention There is considerable art available on cutting tools such as Patents and and more recently and none of these references disclose titanium nitride and titanium carbide bonded with the ture of this We I have discovered that titanium nitride and titanium carbide bonded with the above described nickel molybdenum mixtures when hot pressed as described herein form dense grained bodies of outstanding strength which are also quite hard and resistant to oxidation and Summary In summary this invention is directed to refractory compositions consisting essentially of from to 9 volume percent titanium from 5 to volume percent ium carbide and from 1 to 15 volume percent of metal ing essentially of 20 to 50 volume percent nickel and 50 to 80 volume percent said composition having a density in excess of 99 percent of theoretical and an average grain size of less than 2 and to the method of preparing such solid solutions by heating homogeneous mixtures of titanium carbide and titanium nitride powders having a particle size of less than one micron and nickel and molybdenum ders having a particle size of less than 10 microns to a temperature between and preferably between and and immediately pressing at a pressure between 1000 and 5000 pounds per square inch and then rapidly cooling the resultant The resulting dense compositions are useful in exceptional strength and and can be attractive articles of Description of th Invention This invention is directed to refractory compositio s consisting essentially of to 9 volume percent titanium to volume percent titanium carbide and from 1 to 15 volume percent metal consisting essentially of from 20 to 0 volume percent nickel and from 50 to 80 volume percent said composition having a density excess of 99 percent of theoretical and an average grain size of less than 2 microns and to the method of preparing such solid solutions by heating homogeneous mixtures of finely divided titanium titanium nickel and molybdenum powders to a temperature of between 16500 and and immediately pressing at a between 1000 and pounds per square inch and then rapidly cooling the resultant omponents The titanium nitride and carbide suitable for use in preparing the solid solutions of this invention should have an average particle size of less than one micron and preferably less than Suitable titanium nitride can be obtained ly as mesh powder from Materials for or Consolidated Astronautics Long Island or can be prepared by conventional methods as disclosed in Patent 4ΐβ in Patent or in the Chapter VIII in the book Temperature by Blocher Viiley be obtained com as mesh powder from Materials for Industry or or can be prepared by ventional methods well known to the If the titanium nitride or titanium carbide obtained too large a particle it can be reduced by simply milling the titanium nitride until the desired comminution is The metal povrders suitable for use in this invention should have an average parclcle size of less than 10 microns preferably less than 2 Suitable nickel powder can be obtained commercially as Mond standard grade fine nickel povrder from International Nickel or can be prepared by conventional methods known to the Suitable molybdenum povrder can be obtained cially as standard grade molybdenum povrder mesh from Sylvania Electric Products or can be prepared by ventional methods well known to the The four components are preferably quite pure and it is particularly important that they be substantially free of impurities such as oxygen which have deleterious effects on the solid Minor amounts of impurities normally picked up in milling or mixing the components have little or no deleterious effect on the refractory Thus small amounts of low melting metals such as cobalt or or higher melting metals such as which are ily in milling equipment or can be ted as can small amounts of refractory materials such as nitrides or oxides which are encountered in the pointed out the nitride ordinarily used in compositions of this invention in of from to volume It is preferably in amounts ranging from 60 volume percent to volume percent as such amounts result in refractory composition having a very desirable combination of properties and amounts of titanium nitride range between 60 and 85 volume it is preferred to use from 12 to volume percent of titanium carbide and from to 10 volum percent of It is believed that molybdenum penetrates the titanium carbide lattice and it is preferred that a large excess of metal over that which it believed can be taken up in the titanium carbide lattice not be This is so because a large excess of metal reduces corrosion scratch resistance and hardness of the refractory It is therefore preferred that there be present in the compositions of this invention no more than 1 part by volume of metal per part by volume of titanium Preparation The mixtures of component are prepared much in the manner described in Patent titanium titanium nickel and as described are homogeneously such as by for up to 120 hoursor The mixed powders are then at temperatures of from to and preferably between to and pressures of from 1000 to pounds per square inch followed by rapid cooling of the compact in the manner described in Patent Refractory refractory compacts are characterize by a porosity of less than one percent which translates into a density of at least of and an age grain of less than 2 As mentioned th preferred compositions of this invention contain from 60 to 85 volume percent titanium from 12 to volume cent titanium from 3 to 10 volume percent and have an average grain size of less than one The chemical content as well as the physical properties of the com positions of this invention can be determined by methods well known in the art and described in detail in the Patents and 791 referred to The solid solutions of this invention demonstrate a hardness of from to about A scale and a transverse rupture strength of from about 000 to almost pounds per square This combination of strength and hardness along with their low fine grain size and refractory nature make the compositions of this invention useful in applications requiring corrosion oxidation scratch resistance and wear They are particularly useful in cutting and ing In addition their distinctive color combined with their resistance to scratching and marring make them for use in articles of jewelry such as watch This invention is further illustrated by the ing illustrative examples wherein parts and percentages are by weight unless otherwise Example 1 This is an example of a composition containing 65 volume percent of titanium 30 percent of titanium volume percent of molybdenum and volume percent of nickel The titanium nitride used is of grade mesh available from Materials for and has a specific surface area of square meters per gram as determined by nitrogen An electron micrograph shows dense particles of irregular shapes with sizes between 1 and about 10 the bulk being between 1 and 2 The bon content is percent and the oxygen content is Chemical analysis reveals percent of titanium and percent of The titanium carbide powder used has a nominal average particle size of microns as measured by the Fisher Sizer and a specific surface area of about 10 square meters per gram as determined by nitrogen This titanium carbide powder to microns grade is commercially available from the Adamas Carbide New An electron micrograph of a dry mount preparation shows that the titanium carbide grains are between and 3 microns in diameter and sometimes are clustered in the form of loose The titanium content is about the total carbon content is about the free carbon is around and the oxygen analyses indicate the oxygen content may vary between about to Analysis by emission spectroscopy shows that titanium is the major component and also shows to percent to 2 percent to 2 300 to of 300 to OO ppm of nio 200 to 1000 of 200 to 1000 pp of 100 to 500 of to ppm of to 0 ppm of c a 5 5 ppm of mag The molybdenum powder used is current standard grade available from Sylvania Electric Philadclphi and has a grain size of less than a specific surface area as determined by nitrogen adsorption of square meters per and an average crystallite size of millimicrons as determined by diffraction line An electron micrograph shows the molybdenum pow der consists of grains to 3 microns in diameter clustere together in open Chemical a of the der reveals percent oxygen and no other impurities over 500 The nickel used is a fine available from Nickel containing percent percent and less than ppm The specific surface area of the nickel powder is square meters per gram and its diffraction pattern only which from the line broadening has a crystallite size of 150 Under electron the powder appears as aggregate grains 1 to 5 microns in The powders are milled by loading 6000 parts of preconditioned cylindrical tungste carbide inch long and inch in into a liter steel rolling mill about 6 inches in also charged with 290 parts of saturated paraffinic boiling range The mill is charged with parts of titanium parts of titanium parts of molybdenum a parts o The is then sealed and rotated at 90 revolutions per minute for 5 The mill is then opened and the tents emptied while keeping the milling inserts The mill is then rinsed out with several times til all of the milled solids are The milled powder is transferred to a vacuum and the excess hydrocarbon is decanted off after the pended material has The residual cake is then dried under vacuum with the application of heat until the perature within the evaporator is hetween and and the pressure is less than about millimeters of Thereafter the powder is handled entirely in the absence of The dry powder is passed through a 70 mesh screen in a nitrogen and then stored under nitrogen in sealed plastic A consolidated billet is prepared from the powder by hot pressing the powder in a cylindrical graphite mold having a cavity with a square 1 and inches x 1 and inches and fitted with opposing One piston is held in place in one end of the mold cavity while parts of the powder are charged to the cavity under nitrogen and evenly distributed by rotating the mold and tapping it lightly on the The upper piston is then put in place under hand The assembled mold and contents are then placed in a vacuum chamber of a vacuum hot the mold is held in a vertical and the pistons extending above and below are engaged between opposing graphite rams of the press under pressure of about per square Within a period of a minute the mold is raised into the hot zone of the furnace at and at once the furnace of the at for 2 minutea to uniform heating of the Λ pressure of pound per square inch is then applied the pistons for four Immediately after the mold and contentsj still being held between the opposing moved out of the furnace into a cool zone whore the mold and contents are cooled to dull red heat in about The mold and contents are then removed from the vacuum furnace and the billet is removed from the mold and blasted abrasive grit to remove any adhering Density of the finished piece as determined by accurate weighing and measurement of the dimensions is 8 grams per cubic centimeter corresponds to the theoretical The hot pressed composition is essentially nonporous when examined under 1000 X This property is important since nonporous materials are more corrosion resistant than porous materials of the same chemical the composition consists of an extremely fine The porosity based on optical micrographs is on the scale of Electron micrographs indicate a very grain few grains exceeding 1 or 2 microns in Electron micrographs show an or matrix The micrograph gives the appearance that the metal phase has completely wet the titanium nitride phase or The specimen is very tough and does not break or chip when dropped freely to a hardwood floor from a height of 7 The sample is polished by pressing its faces firmly polishing machine is employed for this A 400 grit diamond wheel is used at 1175 revolutions per minute in the first polishing step and a 1000 grit diamond at revolutions per minute is used in a finishing The sample polished in this manner has an attractive ornamental appearance with a golden A second sample of the same size is fabricated as above indicated and cut so that inch x inch square bars for transverse rupture strength are separated each side of a center Portions of the sample are used for Indentation hardness tests and for other product The average transverse rupture strength as measured by bending the inch x inch test bars on a inch span is about pounds per square The hardness is on the Rockwell A One of the bars used for transverse rupture ment is crushed and ground up in a carbon steel mortar and the powder thus obtained is used in diffraction The diagram obtained shows a strong face centered cubic pattern with a lattice parameter of This pattern corresponds to a titanium carbide solid The lattice parameters of face centered cubic titanium nitride and titanium carbide are about and about parameters are given in kX The composition of this example shows excellent oxidation and corrosion resistance to thermal resistance to and low reactivity with The unusual combination of high and high hardness added to the above mentioned characteristics makes the composition of this example an excellent material for machining Polished specimens of this also used as articles of The procedure of Example 1 is repeated except that the components are used in amounts to give a composition taining volume percent titanium 10 volume cent titanium 1 volume percent molybdenum metal and volume percent Actual amounts loaded in the liter steel mill are parts of titanium nitride parts of titanium carbide parts of molybdenum metal and parts of nickel metal A square billet prepared as in Example 1 wh has a of 1 and inches and about inch thickness is cut so that specimens inch x x about 1 inch are obtained from both sides of a center piece The bars are used for transverse rupture strength measurements the value obtained is pounds per square The rest of the sample is used for Rockwell A hardness measurement and for other Average Rockwell A value obtained is The density is found to be grains per cubic hich is over 99 percent of the theoretical densi The composition of this example shows excellent oxidation and corrosion resistance to thermal resistance to and low reactivity with metals The unusual of high strength and high hardness added to the above mentioned characteristics makes wear corrosion resistant and cutting tools for machining Polished specimens of this composition can also be used as articles of Example The procedure of Example 1 is repeated except that the components are used in amounts to give a composition taining 50 volume percent titanium volume percent titanium 7 volume percent molybdenum metal and 7 volume percent nickel The actual amounts loaded into the liter steel mill are parts of titanium nitride parts of titanium carbide parts of molybdenum metal powder and parts of nickel metal A consolidated billet is fabricated by hot and is tested as indicated in Example The average transverse rupture strength measured is 000 pounds per square inch and the average Rockwell A hardness is The density is found to be grams per cubic which corresponds to the theoretical The composition of this example shows excellent oxidation and corrosion resistance to thermal resistance to and low reactivity ith The unusual combination of high strength and high hardness added to the above mentioned characteristics makes the composition of this example an excellent material for wear corrosion resistant and cutting tools for machining The procedure of 1 except that are u in give a taining volume percent 50 volume 3 volume percent molybdenum metal and 2 volume percent nickel The actual amounts loaded into the liter steel mill are parts titanium carbide parts of titanium nitride parts of molybdenum metal powder and parts of nickel metal A consolidated billet is fabricated by hot pressing and is tested as indicated Average transverse rupture strength measured is pounds per square inch and average Rockwell A ness is The density is found to be grams per cubic which is over 99 of the theoretical The composition of this example shows excellent oxidation and corrosion resistance to thermal resistance to and low reactivity with metals The unusual combination of high strength and high hardness added to the above mentioned characteristics makes the composition of this example an excellent material for wear corrosion resistant parts and cutting tools for machining insufficientOCRQuality

Claims (6)

I CLAIM:

1. A refractory composition consisting essentially of 49.5 to 94 volume percent titanium nitride, 5 to 9.5 volume percent titanium carbide and from 1 to 15 volume percent metal consisting essentially of from 20 to 50 volume percent nickel. and from 50 to 80 volume percent molybdenum, said composition having a density in excess of 99 percent of theoretical and an average grain size of less than 2 microns.

2. A refractory composition of Claim 1 in which the average grain size is less than 1 micron.

3. A refractory composition of Claim 1 wherein volume percentage of titanium carbide exceeds the volume percentage of metal.

4. A refractory composition of Claim 1 in which the volume percent of titanium nitride is βθ to 85, the volume percent of titanium carbide is 12 to j50, and the volume percent metal is from 3 to 10.

5. A refractory composition of Claim 4 in which the average grain size is less than 1 micron.

6. A process for preparing a dense composition of titanium nitride, titanium carbide, nickel and molybdenum comprising heating a homogeneous mixture of 49.5 to 94 volume percent titanium nitride, 5 to 49.5 volume percent titanium carbide and from 1 to 15 volume percent of metal consisting essentially of 20 to 50 volume percent nickel and 50 to 80 volume percent molybdenum to a temperature of from l600° to 1900°C, immediately pressing the mixture at a pressure of from 1000 to 5000 pounds per square inch and rapidly cooling the resultant compact. EHD OF C 1M3- For the Applicants