Application of modern environmentally safe surface hardening technologies during nitrogening

Abstract

Purpose of work. The possibility of using ion-plasma nitriding as an ecologically safe process of surface strengthening to improve service properties of products made of ekonomicalle alloyed ferritic steels was shown.
 Research methods. Samples from steel 03Х8СЮ were investigated. Nitriding was carried out on an installation of the ION-20-I2 model. The pressure and temperature of the process were varied to obtain nitrided layers of different morphology. The structure of the nitrided layers was examined with an Axio Observtr.DLM microscope (Karl Zeis, Germany). The phase composition of the hardened layer of experimental steel was determined on the DRON-type diffractometer according to standard methods. Comparative studies of corrosion resistance were carried out in accordance with GOST 9.908-85.
 Results. It has been established that the method of ion-plasma nitriding can be used to obtain high-quality nitrided layers on the surface of products made of ekonomicalle alloyed ferritic steels. The examined steel is suitable for nitriding in a wide range of technological parameters: temperature, saturation gas pressure. It was found that with an increase in the nitriding temperature, the number of layers, their size and structure in the formed layers change. The optimal mode of ion nitriding (T = 540 °С, t = 4 years, P = 4 mbar) has been determined, which makes it possible to obtain a structure most suitable for solving the problem posed – increasing the corrosion resistance during operation in corrosive environments. Based on the results of determining the phase composition of the samples subjected to ionic nitriding of surface layers, the following phases were found: a- solid solution based on iron and g¢- (MeFe4N)- solid solution based on the chemical compound of iron nitride FeMe4N. The study of corrosion resistance confirmed the efficiency of ion nitriding of steels: the area of corrosion damage on a non-nitrided sample is 85 %, and on a sample after nitriding – 15 %.
 Scientific novelty. The possibility of obtaining nitrided layers of a given composition for economically alloyed ferritic steels by ion-plasma technology using ammonia as a saturating medium has been shown for the first time.
 Practical value. The developed ion nitriding technology is applicable for all economically alloyed ferritic steels and has a number of advantages: reduction of the process by eliminating additional depassivation; reducing the initial cost of electricity by reducing the energy consumption of plasma production; ecological safety, which is associated with the possibility of using an anhydrous environment.