GB2038879A

GB2038879A - Sintered Cemented Titanium Diboride Niobium Nitride

Info

Publication number: GB2038879A
Application number: GB7900117A
Authority: GB
Original assignee: Kennametal Inc
Current assignee: Kennametal Inc
Priority date: 1979-01-03
Filing date: 1979-01-03
Publication date: 1980-07-30

Abstract

A hard wear-resistant composite material, useful for cutting and finishing tools, is produced by sintering an intimate admixture of a binder metal and particles of titanium diboride and niobium nitride. The particles preferably consist of 30 to 80 weight % of TiB2 and 70 to 20 weight of NbN; the binder is Fe, Co, Ni, Mo or alloys thereof and is preferably present in up to 40 weight % of the sinterable material. This material is first sintered under a vacuum or a nitrogen atmosphere, preferably at 1450-1550 DEG C for 30-60 minutes, and then resintered at 1300-1700 DEG C under a pressure of 3000 to 25000 psi.

Description

SPECIFICATION Wear-resistant and Hard Composite Material and Method of Manufacturing it This invention relates to a wear-resistant and hard composite material and to a method for manufacturing it.

Hard wear-resistant and composite materials find their widest use today for tools for use in metalworking, metalforming, cutting tools for all materials and finishing tools for some of the more exotic and hard to work aerospace materials. The extreme hardness of composite materials also makes such a material suitable for use as a hardfacing type material or any other use where hardness and wear resistance are desired properties.

Materials that have been used for such purposes in the past have included diamond composite materials, cemented metal carbides, such as tungsten and titanium carbide, metal nitrides, metal borides, and so on. The materials listed above, while having high hardness and wear-resistant values, are also somewhat expensive to produce and use.

It is an object of the present invention to provide a wear-resistant and hard composite material that has hardness and wear-resistant values suitable for substitution for the abovementioned materials.

According to the invention, there is provided a sinterable material comprising an intimate admixture of a binder metal and particles of titanium diboride and niobium nitride.

The new hard material may comprise 30-80 weight % of titanium diboride (TiB2) and 70-20 weight % of niobium nitride with a binder metal such as iron, nickel, cobalt or molybdenum, or their alloys, preferably in an amount of up to 40 weight %.

The mixture of constituent powder materials may be milled in a ball mill to submicron size powder and then formed by compacting. These compacted pieces are then sintered in vacuum (10--500 micron) or in nitrogen at 1300 to 1700 Centigrade, depending on the composition. These sintered pieces are then sintered again in a hot isostatic pressure furnace at a temperature range of 1300 to 1 7000C and a pressure range of 3000 to 25000 psi, for final densification. The use of a nitrogen atmosphere in both regular sintering and hot isostatic pressure sintering processes makes the sintered hard material having a more nitrided surface and improves the wear resistance.

The composite material of this invention exhibits an excellent wear resistance and high hardness. While satisfactory results may be obtained with all the compositions of the invention, it has been found that the binder content and the processing conditions effect the properties of the composite materials produced.

Preferably, the material of this invention is composed of 50 to 60 weight % of TiB2 and 30 to 40 weight % of NbN with the nickel binder up to 18 weight %.

The preferable processing conditions are: (1) sintering in vacuum (10to 100 micron) at 1450 to 1 5500C for 30 to 60 minutes and cooling in an N2 atmosphere slowiy (about 4000C per hour); and (2) resintering at a hot isostatic pressure of 10000 to 20000 psi at 1450 to 15500C for 30 to 60 minutes.

The following examples serve to illustrate the invention in detail: Example I-Mix 8007 A composition of about 700 gms total weight containing by weight per cent 58 TiB2, 39 NbN and 3 Ni was ball milled in a tungsten-carbidecobalt lined mill with tungsten carbide-cobalt cycloids. This charge was covered with perchloroethylene. The cycloid charge was approximately 50 volume per cent of the mill. All the ingredients plus 3 gms of paraffin wax and 1.5 gm of surfactant as lube additions were charged and milled together for six days.

The starting TiB2, NbN and Ni were commercial grade, 99+weight per cent purity, -325 mesh size. Boron content of the TiB2 was 30.9 weight per cent; nitrogen content of the NbN was 11.3 weight per cent. After milling the powder was dried under inert atmosphere and screened through400 mesh screen. The screened powder was then pill pressed into test pieces at about 24,000 psi and then vacuum sintered at 1 600 degrees Centigrade for 60 minutes.

The vacuum was between 10 and 500 microns pressure during the sintering cycle. The sintered pieces were later reheated under hot isostatic pressure in inert gas at about 16,000 psi and at 1 540 degrees Centigrade for 60 minutes. After the above hot isostatic pressing the samples were examined. Porosity was A5/A6; hardness-93.6 to 94.5 Rockwell "A"; modulus of rupture under three-point testing for two samples was 87,000 psi and 104,000 psi. The microstructure was 1 to 3 micron grain size.

Example 2-Mix 8107 Mix 8107 was composed of by weight per cent 57TiB2, 38N bN, 2.3 Ni and 2.7 molybdenum.

The other starting ingredients were from the same lot as in Example I. The molybdenum used was -325 mesh of 99+ per cent purity, and oxygen content was 0.64 per cent. Milling, lubricants, drying, screening and pressing were as in Example I. This powder was then vacuum hot pressed at 1 600 degrees Centigrade for 30 minutes at 10 to 300 microns pressure. After hot pressing this gave A3/A6 porosity; 94.0 to 95.0 Rockwell "A" hardness; and typically 2 to 3 micron grain size.

Example 3-Mix 8307 Mix 8307 of 2500 gms total weight was composed of by weight per cent 58 TiB2, 38 NbN and 4 Ni. The starting ingredients were the same as in Example I. In this example and subsequent examples the perchloroethylene was replaced by an aliphatic hydrocarbon oil, trade name Soltrol 130 manufactured by Philips Petroleum Company. Milling parameters were similar to Example I except the time was four days. Drying, screening, pressing, vacuum sintering and hot isostatic pressing conditions were similar to Example I except the sintering and hot isostatic treatment temperature was 1 540 degrees Centrigrade. Other parameters were similar to Example I. Examination gave A5/A6 porosity; 93.2 Rockwell "A"; modulus of rupture values were from 62,000 psi to 89,000 psi.

Example 4--Mix 8308 Mix 8308 by weight per cent was 57 TiB2, 38 NbN and 5 Ni. The starting ingredients were the same as in Example 3 except the lube content was increased to 3 weight per cent and the milling was for four days. Drying, screening, pill pressing and vacuum sintering were as in Example I. Hot isostatic pressing was done at 20,000 psi and 1540 degrees Centigrade for 60 minutes. After hot isostatic pressing the properties were: porosity-A3/A5; hardness 95.3 to 95.6 Rockwell "A"; modulus of rupture ranged between 100,000 psi and 132,000 psi.

Grain size was typically 1 to 5 microns.

Example 5Mix 8309 Mix 8309 was composed of by weight per cent 55 TiB2, 36 NbN and 9 Ni. The starting ingredients were from the same lot as in Example 3. Lube content, milling, drying, screening, pressing, vacuum sintering and hot isostatic pressing conditions were the same as for Example 4, Mix 8308. Results were: porosity-A4/A6; hardness-95.0 to 95.5 Rockwell "A"; modulus of rupture ranged from 80,000 to 143,000 psi; grain size ranged from 1 to 5 microns typically.

Example OMix 8310 Mix 8310 was composed of by weight per cent 53 TiB2, 35 NbN and 12 Ni. The starting ingredients were from the same lot as in Example 3. Lube content, milling, drying, screening, pressing, vacuum sintering and hot isostatic pressing were similar to Example 4, Mix 8308.

Results were: porosity-A3/A5; hardness-90.3 to 94.9 Rockwell "A"; modulus of rupture ranged from 77,000 psi to 106,000 psi; grain size was typically between 1 to 5 microns.

Example 7-Mix 8311 Mix 8311 was composed of by weight per cent 51 TiB2, 34 NbN and 15 Ni. The starting ingredients were from the same lot as for Example 3. Lube content, milling, drying, screening, pressing, vacuum sintering and hot isostatic pressing were similar to Example 4. Results are: porosity-A5/A6; hardness-90.1 to 91.6 Rockwell "A"; grain size-1 to 5 microns typically.

Example 8-Mix 8312 Mix 8312 was composed of by weight per cent 50 Tit2; 32 NbN and 18 Ni. The starting ingredients were from the same lot as for Example 3. Lube content, milling, drying screening, pressing, vacuum sintering and hot isostatic pressing were similar to Example 4. Results were: porosity-A4; hardness-88.5 Rockwell "A"; grain size-i to 4 microns typically.

Modifications may be made within the scope of the appended claims.

Claims

1. A sinterable material comprising an intimate admixture of a binder metal and particles of titanium diboride and niobium nitride.

2. A sinterable material as claimed in Claim 1, wherein said particles comprise 30 to 80 weight % of titanium diboride and 70 to 20 weight % of niobium nitride.

3. A sinterable material as claimed in Claim 1 or Claim 2, wherein said metal comprises up to 40 weight % of said sinterable material.

4. A sinterable material as claimed in any one of Claims 1 to 3, wherein said binder metal is selected from the group consisting of iron, nickel, cobalt, molybdenum and alloys thereof.

5. A compact of sintered material comprising a binder metal and particles formed of titanium diboride and niobium nitride.

6. A compact as claimed in Claim 5, wherein said particles comprise 30 to 80 weight % of titanium diboride and 70 to 20 weight % of niobium nitride.

7. A compact as claimed in Claim 5 or Claim 6, wherein said binder metal comprises up to 40 weight % of said compact.

8. A compact as claimed in Claim 6 or Claim 7, wherein said binder metal is selected from the group consisting of iron, nickel, cobalt, molybdenum and alloys thereof.

9. A sinterable material as claimed in Claim 1, substantially as hereinbefore described with reference to any of the Examples.

10. A compact of sinterable material as claimed in Claim 5, substantially as hereinbefore described with reference to any of the Examples.

11. A method of making a hard wear-resistant composite material comprising the steps of forming an intimate admixture comprising powders of titanium diboride and niobium nitride, and a binder metal, sintering said mixture in vacuum or under nitrogen for a predetermined period of time, and then resintering said mixture under pressure and temperature for a predetermined amount of time.

12. A method as claimed in Claim 11, wherein said sintering of said mixture occurs under conditions of temperature ranging from 1450 to 1 5500C for a period of 30 to 60 minutes.

13. A method as claimed in Claim 11 or Claim 12, wherein said resintering of said mixture occurs under conditions of temperature ranging from 1 3000C to 17000 C, and pressure ranging from 3000 to 1 5000 pounds per square inch.

14. A method as claimed in any one of Claims 11 to 13, wherein said mixture is cooled to room temperature after sintering.

1 5. A method as claimed in Claim 14, wherein a nitrogen atmosphere is provided around said mixture during cooling.

16. A method as claimed in any one of Claims 11 to 15, wherein said intimate mixture of powders is ball milled until the powder is submicron in particle size.

1 7. A method as claimed in any one of Claims 11 to 16, wherein said powders are mixed to form a mixture containing titanium diboride in the range of from 30 to 80 weight % of said mixture, and wherein said binder metal is present in the range of from 1 to 40 weight % of said mixture.

18. A method as claimed in any one of Claims 11 to 1 7, wherein said powders are mixed to form a mixture containing niobium nitride in the range of from 20 to 70 weight % of said mixture, and wherein said binder metal ranges from 1 to 40 weight % of said mixture.

1 9. A method of making a hard wear-resistant composite material substantially as hereinbefore described with reference to any of the Examples.

20. A hard wear-resistant composite material made by a method as claimed in any one of Claims 11 to 19.