Acoustical dampening powder metal parts
It has been unexpected found that the sound dampening characteristics of powder metal parts can be dramatically improved by incorporating coarse graphite into the part. This is beneficial in applications where parts to generate noise during operation, such as in gears, rotors and sprockets. Surprisingly, the incorporation of the coarse graphite into such parts does not significantly compromise the strength, durability, wear characteristics, or service life of the part. Such parts can also be manufactured to a high level of tolerance and with good uniformity. Such parts are comprised of a sintered powder metal composition which includes 0.1 weight percent to 5 weight percent of a coarse graphite having a particle size wherein at least at least 30 percent of the coarse graphite will not pass through a 325 mesh screen.
1. A powder metal part which consists of a sintered powder metal composition, wherein the powder metal composition consists of a coarse graphite wherein the coarse graphite is present at a level which is within the range of 1 weight percent to 5 weight percent, optionally nickel, optionally molybdenum, optionally copper, optionally phosphorus, optionally magnesium, optionally silicon, optionally chromium, optionally aluminum, optionally titanium, optionally vanadium, optionally calcium, optionally zinc, and optionally cobalt, and optionally 0.02 to 2% of a standard graphite having a D50 particle size distribution which is within the range of 8 μm to 14 μm and a D90 particle size distribution which is within the range of 15 μm to 21 μm, with the balance of the powder metal composition being iron, wherein the coarse graphite is of a particle size wherein at least 30 percent of the coarse graphite will not pass through a 325 mesh screen, and wherein the powder metal part is a gear.
2. The powder metal part of claim 1 wherein the powder metal part is a pump gear.
3. The powder metal part of claim 1 wherein the powder metal part is a transmission gear.
4. The powder metal part of claim 1 wherein the gear is a helical gear.
5. The powder metal part of claim 4 wherein the helical gear is a herringbone gear.
6. The powder metal part of claim 1 wherein the part has a density which is within the range of 6.6 g/cc to 7.5 g/cc.
7. The powder metal part of claim 1 wherein the part has a density which is within the range of 6.9 g/cc to 7.3 g/cc.
8. The powder metal part of claim 1 wherein the powder metal composition contains the 0.02 to 2% of a standard graphite having a D50 particle size distribution which is within the range of 8 μm to 14 μm and a D90 particle size distribution which is within the range of 15 μm to 21 μm, and wherein molybdenum is present in the powder metal composition at a level which is within the range of 0.4% to 2%.
9. The powder metal part of claim 8 wherein the powder metal composition consists of the iron, the molybdenum, the coarse graphite powder, and the standard graphite, and wherein the coarse graphite is present in the powder metal composition at a level which is within the range of 1.25 weight percent to 3 weight percent.
10. The powder metal part of claim 1 wherein the coarse graphite is present in the powder metal composition at a level which is within the range of 1.5 weight percent to 2 weight percent.
11. The powder metal part of claim 1 wherein the coarse graphite is of a particle size wherein at least 35 percent of the coarse graphite will not pass through a 325 mesh screen.
12. The powder metal part of claim 1 wherein the coarse graphite is of a surface area which is within the range of 2.9 m 2 /g to 3.5 m 2 /g.
13. The powder metal part of claim 1 wherein the coarse graphite is of a surface area which is within the range of 3.0 m 2 /g to 3.3 m 2 /g.
14. The powder metal part of claim 1 wherein the coarse graphite has an average particle size which is within the range of 35 microns to 55 microns.
15. The powder metal part of claim 1 wherein the coarse graphite has a Scott Volume which is within the range of 4.5 g/in 3 to 5.0 g/in 3 .
16. The powder metal part of claim 1 wherein the coarse graphite has a Scott Volume which is within the range of 4.6 g/in 3 to 4.9 g/in 3 .
17. The powder metal part of claim 1 wherein the metal composition contains 0.4% to 2% molybdenum and 1.0% to 4% coarse graphite with the balance of the composition being iron.
18. A powder metal part which consists of a sintered powder metal composition, wherein the powder metal composition consists of a coarse graphite wherein the coarse graphite is present at a level which is within the range of 1 weight percent to 5 weight percent, optionally nickel, optionally molybdenum, optionally phosphorus, optionally magnesium, optionally silicon, and optionally chromium, with the balance of the powder metal composition being iron, wherein the coarse graphite is of a particle size wherein at least 30 percent of the coarse graphite will not pass through a 325 mesh screen, and wherein the powder metal part is a gear.
19. The powder metal part of claim 18 wherein the metal composition contains 0.6% to 1.1% molybdenum, 1.5% to 2% coarse graphite, and 0.5% to 1% standard graphite with the balance of the composition being iron, wherein the standard graphite has a D50 particle size distribution which is within the range of 8 μm to 14 μm and a D90 particle size distribution which is within the range of 15 μm to 21 μm.