Dimensional Change When Compacting and Sintering Metal Powders:

The dimensional change value obtained under specified conditions of compacting and sintering is a material characteristic inherent in the powder.

The test is useful for quality control of the dimensional change of a metal powder mixture, to measure compositional and processing changes and to guide in the production of PM parts.

The absolute dimensional change may be used to classify powders or differentiate one type or grade from another, to evaluate additions to a powder mixture or to measure process changes, and to guide in the design of tooling.

The comparative dimensional change is mainly used as a quality control test to measure variations between a lot or shipment of metal powder and a reference powder of the same material composition.

Factors known to affect size change are the base metal powder grade, type and lot, particle size distribution, level and types of additions to the base metal powder, amount and type of lubricant, green density, as well as processing conditions of the test specimen; heating rate, sintering time and temperature, sintering atmosphere, and cooling rate.

Dimensional Change of Various PM Processing Steps:

The general procedure of measuring the die or a test compact before and after a PM processing step, and calculating a percent dimensional change is also adapted for use as an internal process evaluation test to quantify green expansion, repressing size change, heat treatment changes or other changes in dimensions that result from a manufacturing operation.