Low pressure carburizing and nitriding of fuel injection nozzles

The article describes the newest achievements in heat treatment of fuel injection nozzles made of hot working tool steel applied in diesel engines. Different methods of improving surface properties have been applied by means of vacuum carburizing and vacuum nitriding, especially suitable for elements characterized by difficult shape geometry such as blind holes. Variable process parameters have been considered in terms of sequence and temperature as well as their influence on surface microstructure, hardness and case layer uniformity. A complex technology was invented involving thermo-chemical process supplemented by high pressure gas quenching (HPGQ), deep freezing and tempering. All technological steps were performed in a single chamber vacuum furnace equipped with LPC, LPN and HPGQ.