Transforming Persistent Liquid Phase Sintering into Transient Liquid Phase Sintering

摘要

The following paper describes the process of induced solidification of a persistent liquid phase during the sintering process. Powdered AISI 316L was used as the base material. Persistent liquid phase appearance was induced through the addition of elemental boron, which creates the eutectic liquid during the eutectic reaction with iron. Due to limited solubility of boron in iron, the solidified eutectic phase creates a network of borides surrounding the grains, which lowers the properties of the sinter. For this reason the persistent liquid phase was transformed into a transient one by adding the powdered nitrogen carrier, which tends to react only when a certain temperature is reached. By adding the nitrogen carrier to the Fe-B composition, the crystallographic network of solidified eutectic may be changed into one of a different molar volume and of a different melting temperature. Results indicate that sinters of high dimensional precision, high density and of high mechanical properties may be obtained by using a proper combination of adding elemental boron and a nitrogen carrier.