HIGH-PERFORMANCE MICROENCAPSULATED POWDERS FOR VARIOUS P M APPLICATIONS/

Microencapsulation and warm pressing of metal powders was developed in the 80's at GM. A direct fire ignition system with two P/M iron elect romagnetic cores, has been in production in Europe since 1990. A Nd-Fe -B powder, Magnequench, is microencapsulated and the coated powder has been sold commercially to a camera manufacturer for P/M molding since 1991. These net shape P/M parts have application in AG and pulsed DC electromagnetic systems, as well as structural, DG electromagnetic sys tems, and permanent magnet systems. The parts have high green strength , high molded density and good particle to particle insulation for AC applications. Because of the increased green strength and the increase d flowability during molding, thin walled parts and parts with a compl ex geometry can now be made by net shape P/M techniques. These P/M par ts can then be sintered for DC or structural applications or used as m olded, for AC applications. One major disadvantage of the AC and pulse d DG applications has been lower output compared to the current lamina tion system. Now, however, a new microencapsulated powder has been dev eloped and is nearing production. This new material has raised the per meability and lowered the eddy current losses so that the output of ou r ignition coil has been improved by 30%. Another microencapsulated po lymer system has proven useful in structural and DC electromagnetic sy stems. The new system yields higher green strength, higher densities, and better powder flow during molding. Because of these improvements, the sintered part has improved output and strength. This polymer coate d product has helped to eliminate cracks in one of our alternator appl ications.