Comparison of thermal and microwaveassisted plasma sintering of nickel–diamond composites

Abstract

There is considerable interest in processing technologies which can lead to more energy efficient sintering of metal powders. Microwave sintering has recently been shown to reduce energy usage as the volumetric heating process is considerably more efficient than resistance heating. RF plasma sintering meanwhile has been shown to deliver heat via uniform excitation of the processing gas resulting in ion bombardment of the workpiece. In this study the use of a rapid, novel microwave-assisted plasma sintering (MaPS) technology for processing of nickel-diamond metal matrix composites is evaluated. Nickel powder and polycrystalline diamond were mixed to prepare 20 mm discs under uniaxial compaction pressures of 100, 200 and 300 MPa. The discs were fired in a low pressure microwave plasma under a hydrogen atmosphere. For comparison, discs were also sintered using conventional tube furnace firing. The MaPS sintering is very rapid with full disc strength of >1000N, based on 3-point bend tests, being achieved within 10 minutes compared with 8 hours for furnace treatment. This study demonstrates that the microwave-assisted plasma sintered discs produced similar or superior performance to discs fired using furnace firing conditions but with sintering cycle time reduced by up to 95%.

Future of clay-based construction materials – A review

“…and wavelengths between 1mm and 1m in free space [31,72]. Standard microwave for scientific or industrial processing operates at a frequency of 2.45GHz [29,31,72,73].…”

“…Additionally, all the reviewed studies indicate a considerable reduction in processing time by using microwave heating compared to a conventional electrical oven. This is because the volumetric heating process is significantly more efficient in comparison with resistance heating [72,85].…”

Novel rapid discharge sintering technique for damage-free diamond metal matrix composites

“…8,9 We have previously investigated the use of RDS for the sintering of nickel powders. 10 In the present study, use of RDS is extended to diamond/nickel metal matrix composites (MMCs) and the results compared with furnace treatments. Nickel and diamond powders were chosen as the test materials as they are used in a wide range of engineering components to enhance wear resistance, mechanical strength, thermal expansion, electrical conductivity and magnetic permeability.…”

“…We have previously investigated the use of RDS for the sintering of nickel powders 10. In the present study, use of RDS is extended to diamond/nickel metal matrix composites (MMCs) and the results compared with furnace treatments.…”