Iron-based composite powder

Abstract

A new iron-based powder containing a plurality of composite particles composed of a ferritic iron or iron-based porous 5 structural particles having at least one particulate friction modifier distributed in the pores and cavities of the structural particles and further containing at least one particulate stabilizer-sealer. The composite particle is especially suited to be used as a functional material in friction formulations such as brake pads and enable replacement of copper or copper-based materials used in such friction 10 material formulations.

Claims

1. A powder comprising a plurality of composite particles wherein said composite particle is composed of an iron or iron- based porous structural particle having a ferritic structure, the composite particle having at least one particulate friction modifier distributed in the pores and cavities of the structural particles and further comprising at least one particulate stabilizer-sealer, wherein the particulate friction modifier and the particulate stabilizer-sealer are in free form.

2. The powder according to claim 1 wherein the content of friction modifiers are 0.1-10% by weight of the powder.

3. The powder according to claim 1 wherein the content of friction modifiers are 2-6% by weight of the powder.

4. The powder according to claim 1 wherein the powder has a particle size distribution such that 100% is below 20 mesh (850 m) and 90% is above 635 mesh (20 m).

5. The powder according to claim 1 wherein the powder has a particle size distribution such that 100% is below 60 mesh (250 m) and 90%>is above 325 mesh (44 m).

6. The powder according to claim 1 wherein AD is between 1.2 and 2.5 g/cm.sup.3.

7. The powder according to claim 1 having SSA between 1-30 m.sup.2/g.

8. The powder according to claim 1 having SSA between 2-20 m.sup.2/g.

9. The powder according to claim 1 wherein the amount of the composite particle with ferritic structure is 85% to 97% by weight.

10. The powder according to claim 1 wherein the particulate friction modifier is chosen from the groups of: carbon containing materials selected from graphite, coke, coal, activated carbon, carbon black; minerals selected from talc, mica, calcium fluorite; and other inorganic materials selected from molybdenum disulfide (MoS.sub.2), hexagonal boron nitride (h-BN), manganese sulfide (MnS), antimony sulfide (SbS.sub.3 or Sb.sub.2S.sub.5).

11. The powder according to claim 10 wherein the friction modifier is chosen from graphite, talc, MoS.sub.2, h-BN, MnS and SbSs.

12. The powder according to claim 1 wherein the amount of particulate stabilizer-sealer is 0.1-5% by weight of the powder.

13. The powder according to claim 1 wherein the amount of particulate stabilizer-sealer is 1-3% by weight of the powder.

14. The powder according to claim 1 wherein the particulate stabilizer-sealer is chosen from the group of: clay minerals, cement, calcium oxide (CaO) and calcium hydroxide (Ca(OH).sub.2, and water glass.

15. The powder according to claim 14 wherein the stabilizer-sealer is chosen from bentonite, kaolin, Portland cement, calcium oxide, and sodium silicate.

16. A component prepared from the powder according to claim 1.

17. The component according to claim 16, wherein the component is friction material of a brake pad.

18. A brake pad containing a powder according to claim 1.

19. A method for producing the powder of claim 1 comprising the steps of a) providing an iron or iron based porous powder comprising a plurality of particles, wherein the particle is composed of an iron or iron- based porous structural particle having a ferritic structure, wherein the particle size of the iron or iron based porous powder is below 850 m, and a minimum of 90% of the particles is above 45 m, and having apparent density (AD) between 1-2 g/cm.sup.3, and providing a friction modifier chosen from the group of: carbon containing materials selected from graphite, coke, coal, activated carbon, carbon black; minerals selected from talc, mica, calcium fluorite; and other inorganic materials selected from molybdenum disulfide (MoS.sub.2),hexagonal boron nitride (h-BN), manganese sulfide (MnS), antimony sulfide (SbS.sub.3 or SbjSa), b) mixing the iron or iron-based powder with 0.1-10% by weight of the powder, with said friction modifier for a period of time of 1-30 minutes, c) providing a stabilizer-sealer chosen from the group of: clay minerals; cement; calcium oxide (CaO) and calcium hydroxide (Ca(OH).sub.2; and water glass, d) mixing 0.1-5% by weight of the powder, of said stabilizer-sealer with the mix obtained in step b) for a period of time of 1-30 minutes, e) optionally adding 0.5-10% by weight of the powder of water and mixing for a period of time of 1-30 minutes, f) subjecting the obtained mixture in step e) for a drying process at 50-150 C., g) recovering the obtained powder, and step c) may be performed before step a) or may be performed before step b).

20. The method of claim 19, wherein in step a) a minimum of 90% of the particles is above 75 m, wherein the apparent density (AD) is between 1.2-1.8 g/cm.sup.3.

21. The method of claim 19, in step b) mixing the iron or iron-based powder with 2-8% by weight of the powder, with said friction modifier for a period of time of 1-30 minutes.

22. The method of claim 19, in step d) mixing 1-3% by weight of the powder, of said stabilizer-sealer with the mix obtained in step b) for a period of time of 1-30 minutes.

23. The method of claim 19, in step e) adding 1-5% by weight of the powder of water and mixing for a period of time of 1-30 minutes.

24. The method of claim 19, in step f) subjecting the obtained mixture in step e) for a drying process at 75-125 C.

Description

BRIEF DESCRIPTION OF THE FIGURE

(1) FIG. 1 shows result from dynamometer test of reference brake pad and brake pads containing the powder composite particles according to an embodiment of the present invention.

EXAMPLES

(2) Apparent density, AD, was measured according to MPIF standard test method for metal powders and powder metallurgy products No. 03:2012.

(3) Specific Surface AREA, SSA, was measured according to ISO 9277:2010 BET method.

(4) X.sub.50 and X.sub.95 was measured according to ISO 13320:2009 laser diffraction method.

(5) Flow was measured according to MPIF standard test method for metal powders and powder metallurgy products No. 02:2012.

(6) Hardness was measured according to MPIF standard test method for metal powders and powder metallurgy products No. 43:2012.

(7) Strength was measured according to MPIF standard test method for metal powders and powder metallurgy products No. 41:2012.

Example 1

(8) Preparation of the powder composite particles.

(9) 1000 grams of porous hydrogen (H.sub.2) reduced iron powder having an iron content more than 98% was mixed with 50 grams of graphite in a paddle mixer for a period of 10 minutes. After this first mixing step, 30 grams of a clay mineral, bentonite, was added to the mixer and further mixed for a period of 6 minutes. 25 ml of water was thereafter sprayed into the mixer during mixing and continue to mix for a period of 5 minutes. After the wet mixing, the powder composite particles are dried at 60 C. for 2 hours.

(10) The following table 1 shows the properties of the iron powder, the graphite and the clay used.

(11) Properties of Materials Used for Producing the Powder Composite Particles

(12) TABLE-US-00001 TABLE 1 Iron powder Graphite Clay AD [g/cm.sup.3] 1.43 0.09 0.34 SSA [m.sup.2/g] 0.25 250 75 X.sub.50 [m] 2.0 3.5 X.sub.95 [m] 9.4 10.0 Flow [s/25 g] 33.5 No flow No flow Sieve analysis +40 mesh (+420 m) [%] 0 N.A. N.A. +100 mesh (+149 m) [%] 65.5 N.A. N.A. +200 mesh (+74 m) [%] 26.0 N.A. N.A. 200 mesh (74 m) [%] 8.5 N.A. N.A.

(13) The following table 2 shows the properties of the iron powder used, the intermediate products and the final composite powder (1).

(14) TABLE-US-00002 TABLE 2 After Iron After first second Composite powder mixing mixing powder (1) AD [g/cm.sup.3] 1.43 1.51 1.49 1.62 SSA [m.sup.2/g] 0.25 12.7 14.9 13.7 Flow [s/25 g] 33.5 No flow No flow 28.3 Sieve analysis +40 mesh (+420 m) [%] 0 0 0 0 +100 mesh (+149 m) [%] 65.5 65.4 66.0 60.0 +200 mesh (+74 m) [%] 26.0 25.4 24.2 28.5 200 mesh (74 m) [%] 8.5 9.2 9.8 11.5

(15) As can be seen from table 2, there is no significant change in particle size distribution between the iron powder used and the final composite powders. Compared to the intermediate products that are unable to flow freely due to the fine additive addition, the composite powder exhibits a good flow rate indicating that the stabilizer-sealer was successfully coated on the surface of iron particles to seal the friction modifier inside of iron particles through the wet and dry process. A good flow rate also facilitates handling of the powder and manufacture of the friction material. AD is changed to a minor degree indicating that the powder composite particles maintain its particle morphology. Due to the addition of friction modifier and stabilizer-sealer, however, the SSA of the final composite powder is greatly increased compared to the iron powder. The improved flow, similar AD and particle size distribution, and increased SSA were the evidence for the composite powder constructed well with the friction modifier and stabilizer-sealer.

Example 2

(16) A second composite powder, composite powder (2), was prepared according to the procedure described in EXAMPLE 1 with the exception of that instead of 50 grams of the graphite as friction modifier, 40 grams of the same type of graphite and 10 grams of hexagonal boron nitride was used. Table 3 shows the properties of the hexagonal boron nitride.

(17) TABLE-US-00003 TABLE 3 h-BN AD [g/cm.sup.3] 0.16 SSA [m.sup.2/g] 12.5 X.sub.50 [m] 0.9 X.sub.95 [m] 6.5

(18) Properties of the intermediate products and the final composite powder, composite powder (2) was measured, results of the measurements according to table 4.

(19) TABLE-US-00004 TABLE 4 After Iron After first second Composite powder mixing mixing powder (1) AD [g/cm.sup.3] 1.43 1.53 1.50 1.65 SSA [m.sup.2/g] 0.25 10.4 12.6 11.9 Flow [s/25 g] 33.5 No flow No flow 30.1 Sieve analysis +40 mesh (+420 m) [%] 0 0 0 0 +100 mesh (+149 m) [%] 65.5 66.4 66.1 65.2 +200 mesh (+74 m) [%] 26.0 24.7 24.8 25.8 200 mesh (74 m) [%] 8.5 8.9 9.1 9.0

(20) As can be seen from table 4, there is no significant change in particle size distribution between the iron powder used and the final composite powders. Compared to the intermediate products that are unable to flow freely due to the fine additive addition, the composite powder exhibits a good flow rate indicating that the stabilizer-sealer was successfully coated on the surface of iron particles to seal the friction modifier inside of iron particles through the wet and dry process. A good flow rate also facilitates handling of the powder and manufacture of the friction material. AD is changed to a minor degree indicating that the powder composite particles maintain its particle morphology. Due to the addition of friction modifier and stabilizer-sealer, however, the SSA of the final composite powder is greatly increased compared to the iron powder. The improved flow, similar AD and particle size distribution, and increased SSA were the evidence for the composite powder constructed well with the friction modifier and stabilizer-sealer.

Example 3

(21) A third composite powder, composite powder (3), was prepared according to the procedure described in EXAMPLE 1 with the exception of that instead of 50 grams of the graphite as friction modifier, 70 grams of manganese sulfide (MnS) and 30 grams of mica was used. Table 5 shows the properties of the manganese sulfide and the mica.

(22) TABLE-US-00005 TABLE 5 MnS Mica AD [g/cm.sup.3] 1.02 0.21 SSA [m.sup.2/g] 1.3 9.3 D.sub.50 [m] 5.6 4.9 D.sub.95 [m] 8.8 14.3

(23) Properties of the intermediate products and the final composite powder, composite powder (3) was measured, results of the measurements according to table 6.

(24) TABLE-US-00006 TABLE 6 After Iron After first second Composite powder mixing mixing powder (1) AD [g/cm.sup.3] 1.43 1.55 1.53 1.71 SSA [m.sup.2/g] 0.25 0.59 2.84 2.34 Flow [s/25 g] 33.5 No flow No flow 27.2 Sieve analysis +40 mesh (+420 m) [%] 0 0 0 0 +100 mesh (+149 m) [%] 65.5 61.0 60.2 62.9 +200 mesh (+74 m) [%] 26.0 28.4 27.3 27.3 200 mesh (74 m) [%] 8.5 10.6 12.5 9.8

(25) As can be seen from table 6, there is no significant change in particle size distribution between the iron powder used and the final composite powders. Compared to the intermediate products that are unable to flow freely due to the fine additive addition, the composite powder exhibits a good flow rate indicating that the stabilizer-sealer was successfully coated on the surface of iron particles to seal the friction modifier inside of iron particles through the wet and dry process. A good flow rate also facilitates handling of the powder and manufacture of the friction material. AD is changed to a minor degree indicating that the powder composite particles maintain its particle morphology. The SSA of the final composite powder is also increased compared to the iron powder due to the addition of friction modifiers and stabilizer-sealer. The improved flow, similar AD and particle size distribution, and increased SSA were the evidence for the composite powder constructed well with the friction modifier and stabilizer-sealer.

Example 4

(26) Evaluation on Phase Stability of Composite Powder

(27) The composite powder 1 and composite powder 2 obtained in EXAMPLE 1 and 2 were used to evaluate their ferritic phase stability at elevated temperature compared to the iron powder with and without graphite addition. After mixed with 1% by weight Acrawax C as a compaction lubricant, the powder mix was compacted into transverse rupture strength (TRS) specimen at 6.5 g/cm.sup.3 according to MPIF standard test method for metal powders and powder metallurgy products No. 41:2012. The compacted samples were then heated at 900 C. and 1120 C. respectively in 100% nitrogen atmosphere for 30 minutes. After the heated samples were cooled to room temperature, hardness, according to MPIF standard test method for metal powders and powder metallurgy products No. 43:2012, and strength, according to MPIF standard test method for metal powders and powder metallurgy products No. 41:2012, of each heated material were measured. The results were shown in table 7.

(28) TABLE-US-00007 TABLE 7 Composite Composite Iron powder Iron powder + powder 1 powder 2 only 0.8% graphite Material (invention) (invention) (reference) (reference) Graphite 5.0 4.0 <0.05 0.8 content (%) 900 C. heated Hardness 34 HRH 36 HRH 37 HRH 96 HRH Strength 35 28 56 294 (MPa) 1120 C. heated Hardness 33 HRF 19 HRF 35 HRF 62 HRB Strength 70 77 105 532 (MPa)

(29) As can be seen from table 7, the composite powders presented similar hardness and strength compared to the iron powder without graphite addition, indicating that the composite powders still maintain the ferritic phase well, even it contained large amount of graphite and heat treated at 900 C. and 1120 C. respectively. For the iron powder with 0.8% graphite addition, however, it showed much harder and much higher strength than the composite powders due to the diffusion of carbon from added graphite to form cementite containing phase. The tests provided evidence for the composite powders according to the present invention having stable ferritic phase, or austenitic phase in the structural iron powder when subjected to temperatures up to 1120 C.

Example 5

(30) Preparation and Testing of Friction Materials

(31) A typical non-asbestos organic (NAO) brake pad formulation was selected for friction tests. This formulation contains 8% by weight copper powder together with binder, lubricants, abrasives, fillers, etc. various powdered materials according to the following table 8, as reference friction material. The same powdered materials as used for preparation of the reference material were used for preparing the test friction materials with the exception of that copper powder were fully replaced with composite powder 1 and composite powder 2, in the same amount by weight, respectively. The composite powder 1 and composite powder 2 were made from EXAMPLE 1 and 2 respectively. Other powdered materials include phenolic resin, cashew nut shell oil, graphite, antimony trisulfide, zirconium silicate, aluminum silicate, magnetite, mica, potassium titanate, rubber, aramid fiber, barytes.

(32) TABLE-US-00008 TABLE 8 Compositions of friction material (% by weight) Material Material containing containing Reference composite composite NAO formulations material powder (1) powder (2) Binders (%) 18 18 18 Lubricants (%) 12 12 12 Abrasives (%) 33 33 33 Fillers (%) 29 29 29 Copper powder (%) 8 Composite powder (1) or (2) (%) 8 8

(33) All powdered materials including the copper and the composite powders were weighed accurately according to their designated amount, added into a vertical mixer for mixing and mixed for 15 minutes. A total of 2 kg mixed material was made for each mix. The mixes were then loaded into a brake pad mold, which fits the Ford Crown Victoria (1999) test assembly on the full-scale dynamometer. The molded brake pad samples were hot pressed for 15 minutes at 175 C. and post cured in an oven at 180 C. for 4 hours.

(34) Friction Test

(35) The produced brake pad samples were tested on a single-ended inertial type brake dynamometer using SAE J2430 procedure. Original equipment manufacturer (OEM) grade cast iron disc rotors and calipers were used in the tests. Based on the full-scale dynamometer test results, a Brake Effectiveness Evaluation Procedure (BEEP) was used to evaluate the friction performances. The BEEP evaluation results are shown in table 9.

(36) TABLE-US-00009 TABLE 9 Pad containing Pad containing Reference 8% 8% pad (8% composite composite BEEP criteria Min Max Cu) powder (1) powder (2) Effectiveness space 0.179 0.473 0.36 0.35 0.30 [Nm/kPa] Cold effectiveness 500 203 170 204 [N] Fade snubs 500 94 68 64 [N] Hot performance 1073 1097 1605 1691 S1 [Nm] Hot performance 1367 2575 3396 3685 S2 [Nm] Structural integrity 90 100 100 100 [%] Overall assessment pass pass pass

(37) As evident from table 9, all tested brake pads passed the test. It can also be noted that brake pads containing the composite particles according to the present invention even exceeded the performance of the reference brake pad related to some aspects such as hot performances.

(38) Thermal Fade Resistance Test

(39) The SAE J2430 full-scale dynamometer tests also evaluated thermal fade resistance of the brake pad samples. Thermocouples were embedded below the friction surface of brake pad samples. The brake pads were subjected to make repeated stops at a speed of 120 km per hour without the brake assembly was cooled so that the temperature increased from 50 C. at the start to 325 C. at the end of test FIG. 1 shows the thermal fade test results. It is evident that the brake pads containing the composite particles according to the present invention have good Thermal Fade Resistance, which even exceeds the reference material.

(40) Wear Test

(41) The SAE J2430 full-scale dynamometer tests also evaluated the brake pads and disc wear after the tests were completed. The thickness and weight of the brake pad samples and disc rotor were accurately measured prior to and after the test. Table 10 shows the results of wear for each tested brake pad samples.

(42) TABLE-US-00010 TABLE 10 Pad containing 8% Pad containing 8% Reference composite composite pad (8% Cu) powder (1) powder (2) Inboard pad, thickness loss [mm] 0.75 0.68 0.53 Weight loss [g] 6.10 1.13 1.26 Outboard pad, thickness loss [mm] 0.47 0.63 0.56 Weight loss [g] 4.3 1.00 1.00 Rotor wear thickness loss [mm] 0.035 0.026 0.011

(43) Compared to the reference pad, the composite containing brake pads exhibits similar pad wear in thickness but much less weight loss in both inboard and outboard pad, and less wear in the disc rotor.