Fabrication of Low—Permeability Gas-Flow Control Devices

Abstract

A commercially practicable P/M process for producing gas-flow control devices is outlined. Considerations favouring a P/M approach are presented and the importance of powder characteristics is stressed. The technology for producing units with a gas flow of the order of 10⁻⁴cm³/s is outlined and the influences of sintering, compaction, and coining are discussed in detail. The generalizations resulting from this study are applicable to units ranging in flow rates from 10⁻² to 10⁻⁸ cm³/s. Density reproducibility through compaction-pressure control is shown to be the most important factor in producing repeatable flow rates. Coining-tool geometry, compaction pressure, sintering kinetics, permeability, density, and pore size are variables considered in the analysis.