Powder Metal Gears

Increasingly, it has been seen that the gear designers have understood the advantages and flexibility of powder metallurgy. Powder metal gears have found applications in a variety of industries. Like appliances, office machinery, automobiles, outdoor power equipment, power hand tools etc. The powder metallurgy process is quite adept in producing range of close tolerance gears. They can make gears that has strengths up to 1240 Mps. This is done at most economical prices and in volume quantities. Common gears that are manufactured with powder metallurgy techniques include spur, helical, bevel, face, spur-helical, sprockets etc.

Advantages of Powder Metal gears
Compared to a conventional gear manufacturing process, the powder metallurgy process has the ability to offer several distinct advantages. This is particularly visible, with gears made out of powder metallurgy eliminating the need for machining and there is no scrap losses either. There is easy provision to form internal configurations (splines, keys, keyways). These are formed simultaneously with the gear profile while the molding process is on. Following process advantages are associated with powder metal gear manufacture:

Manufacturing of Powder Metal Gears
There is two methods available for the production of Powder metal gears.

Press and Sinter method
This is a typical process where fine metal powder along with alloying ingredients are molded under very high pressure. Which is then fired to fuse the mass. It is a relatively high-production technology for manufacturing high-strength gears at a comparatively low cost. Metals typically used for the purposes of gears can be iron-based mixtures, bronzes and even brasses. Powder metals though costly, but it offsets this by the advantage of minimal scrap losses.

 

Name	Composition(%)	Specification Designation	Ultimate Tensile Strength (psi)	Comments
Iron-Copper Alloy	Copper 7-11 Iron-remainder	Copper 7-11 Iron-remainder	40,000	Gives a controlled amount of porosity;perfect for lubricant impregnation
Copper-Steel Alloy	Iron 94,0 min. Copper 1.0 - 4.0 Other 2.0 max.	ASTM B310-58T Class A Type II	60,000	Fair enough for Gear applications subject to high impact
Carbon-Steel Alloy	Iron 95.5 min. Silicon 0.3 max. Aluminum 0.2 min Other 3.0	SAE Type 6 Class C ASTM B310-58T	50,000	Excellent wear resistance
Alloy Steel AISI 4630	Carbon 0.30 Manganese 0.50 Silicon 0.25 Nitrogen 1.7 Molybdenum 2.5 Iron balance		160,000	High strength sintered powder material
Phosphor Bronze	Copper 87.0 Min. Tin 9.5 - 10.5 Phosphor 0.3 - 0.5 Other 1.5 max.	SAE Type 1 Class A ASTM B202-58T Type 1 Class A Mil B 5687A Type 1 Comp.A	30,000	One of the strong sinter bronzes

 

Gear Rolling
To do away and improve upon the traditional "press and sinter" method Gear rolling is now increasingly used for making gears in powder metallurgy. This is because gear production have not been able to produce the same level of gears as with that of precision grinding. This process can take the manufacturing standards to AGMA 10 or more.