Effect of sintering conditions on mechanical strength and gas permeability of long porous Inconel 625 tubes for hot gas filtration

Abstract

The sintering responses of Inconel 625 prealloyed powder (powder size: 80–180 μm accounting for 96 wt-%) were first assessed using dilatometry. Then, sintering of Inconel 625 tubes (Φ54 mm × 1000 mm), shaped by cold isostatic pressing from prealloyed powder at 170 MPa, was studied at temperatures between 1180 and 1260°C in vacuum and hydrogen. Sharp, rapid shrinkage of Inconel 625 prealloyed powder was observed at 1240°C when sintered in vacuum, while this temperature was postponed to 1260°C when sintered in hydrogen due to the cooling effect of the large hydrogen gas flow. It is shown that sintering in hydrogen is better suited to the fabrication of high performance porous Inconel 625 tubes than sintering in vacuum. The preferred isothermal sintering conditions were determined to be sintering in hydrogen at 1240°C for 120 min, which resulted in balanced mechanical strength and gas permeability. The as sintered porous Inconel 625 tubes (Φ54 mm × 1000 mm) have been used to filter hot (up to 400°C) gas mixtures of SiHCl₃ and HCl in continuous industrial operations for 6 months and demonstrated outstanding performance.

Keywords:

• Inconel 625
• Porous filter
• Sintering
• Permeability
• Mechanical strength

Acknowledgement

This work is funded by the National High Technology Research and Development Program of China (grant no. 2012AA03A610).