Powder Metallurgy Technologies and Methods

Powder metallurgy materials can be carburized and quenched in the same way as general steel materials, and carburizing and quenching are used for products that require hardness and strength.
Due to the presence of pores, carburizing is performed extending deep from the surface, requiring different quenching conditions than for general steel.

This is a method that allows hardening in an even more localized area than induction hardening.
The surface of the material is heated rapidly by laser and then hardened by self-cooling (heat conduction).
Compared to other hardening methods, the deformation caused by hardening is smaller and it is easier to control.

Powder metallurgy is a process in which powder is solidified in a die and is formed into a shape. By transferring the die shape, complex shapes can be mass-produced without machining.
The elimination of machining allows for extremely high material yields and reduced machining costs, making it possible to reduce costs compared to other methods.
However, machining is required for shapes that cannot be removed from the die.

This is an example adopted for the valve case, a shock absorber component. In order to intentionally reduce the contact area as a countermeasure against noise caused by valve adsorption, minute concave and convex dimples are formed without machining. By forming with a die which has minute concave and convex dimples provided by electrical discharge machining on its surface, the concave and convex dimples are transferred to the product.

Sintered parts have a reduced strength and high water (oil) absorbency due to the presence of pores inherent in powder metallurgy. In addition, the sintered parts have a disadvantage of rusting due to the surface activated by sintering.
In order to compensate for these, steam treatment under high temperature heating is performed to form a triiron tetraoxide film on the surface, which improves surface hardness, seals pores, and prevents rusting.

Plating can be applied in the same way as general steel materials. However, due to the presence of pores inherent in powder metallurgy, it is required to perform pore sealing treatment in advance such as resin impregnation.

This is a technology for joining multiple parts using brazing material during sintering.
By joining multiple parts, complex shapes such as hollow shapes can be obtained.

This is an example adopted for the piston, a shock absorber component. Conventionally the oil path connecting the upper and lower surfaces were made by drilling, but by bonding the two parts together in a concavo-convex configuration, an offset oil path connecting the upper and lower surfaces can be ensured without machining.

When improving material characteristics, expensive raw materials are added and used in some cases, but this can lead to higher raw material costs. In order to solve this problem, there is a method called double-layer forming, in which expensive materials are used only in required parts. This is a method unique to powder metallurgy, in which expensive material is first temporarily compacted, and then the die cavity is filled with inexpensive material to obtain a product with a double-layered cross-section as shown in the figure on the right.

Multiple parts can be combined using joining techniques such as welding, brazing, bonding, plastic inserts, and caulking. This allows for combination of parts with different materials or with resin, and creation of complex shapes.

Resin insert molding and banding techniques can be used to combine sintered parts with resin.

MIM (Metal Powder Injection Molding) is a process to obtain shapes by injection molding like plastic by using a material that is a mixture of metal powder and resin. This process can produce shapes that cannot be achieved by conventional powder metallurgy compression molding.

Machining is possible in the pre-sintered state of the compact. Since the compact is only solidified powder, this method provides excellent machinability, shortens machining time, and greatly improves tool life. It is mainly used for rough machining and for machining parts that do not require high precision.

Sintered Vent® is a product manufactured by applying the sintering process of powder metallurgy. The product has a large number of paralleled, linear micro pores produced by infiltration, allowing for air and gas venting.
Also known as an air vent or gas vent, the product is widely used as a gas vent during aluminum casting or resin molding.