Design Characteristics
Porous sintered metal materials have the following unique characteristics;
- Good mechanical properties
- Rigid, non-shedding structures that maintain porosity characteristics during service
- Superior Temperature and Corrosion Resistance
- Controlled Permeability that can be tailored to meet specific applications
- Ability to be cleaned for economical reuse
- High Surface Area
For example, the superior mechanical properties of porous bronze, stainless steel or nickel alloys withstand the rugged service requirements of elevated temperature and higher pressure environments where other porous materials such as papers, synthetic fibers and plastics can not be used.
Design engineering information is readily available for many of the porous material characteristics such as density, pore size and distribution, bubble point, permeability and mechanical properties. However, the unique characteristics of porous P/M materials often require additional design engineering considerations since properties such as elevated service temperature and corrosion resistance properties are very different from 100% dense material properties.
The density, pore size, pore size distribution and permeability will determine the overall performance of a porous material in an application. The interrelationship of these four characteristics often allows the design engineer to specify only one or two of these factors. For example, testing has shown that the permeability of a porous part can be accurately predicted if the density and the initial powder particle characteristics are known for a particular processing method. The initial powder particle size controls the pore size and distribution when sintered to a specified density. The permeability is related to the pore size and pore distribution.
As the density of the porous component increases, the mechanical properties are increased, but the overall permeability is reduced since there is a proportional decrease in the porosity. Several density measurement methods for porous materials are described by International Organization for Standardization (ISO) Document 2738. An estimate of the part density can also be easily calculated by measuring the part weight and dividing by the part volume.
Other porous material characteristics can be estimated from wrought (or full density P/M) products since higher density products have more extensive test data available in the literature. Material properties such as thermal conductivity, thermal expansion, fatigue, electrical conductivity and magnetic properties are highly dependent on porosity and generally decrease as porosity increases. Limited availability of design engineering data for porous materials often results in the need for actual testing in the intended application prior to use.
8 MB
