Study of the Influence of Electrolytic-Plasma Treatment on the Tribological Properties of High-Speed Steel: High Temperature Testing of Nitrided Layers High-Speed Steel

Introduction

The development of engineering technologies largely depends on the technical level of tool production. Thus, one of the problems of environmental protection in mechanical engineering is the high wear resistance of metalworking tools under various conditions of the loading process when machining parts by cutting. The durability of the tool depends not only on the properties of the material, implemented by the technology of formation and volumetric hardening, but also in the manifestation of the degree of surface properties. Its role in ensuring the performance properties of products is constantly increasing, which, along with the widespread use of traditional methods of chemical-thermal treatment, has contributed to the emergence and development of a new direction-surface engineering by methods of energy and physical-chemical effects. The implementation of this concept when choosing a material will improve the performance properties of the tool, and in some cases reduce the consumption of expensive materials. So, recently, due to the use of protective coatings and surface hardening, high-speed steels are increasingly being used and produced, which has made it possible to reduce the cost of expensive hard alloys. At the same time, an important role in the application of protective coatings and surface hardening is played by the use of resource-saving technologies that help reduce resource and energy costs and increase labor productivity.

The most promising method of surface hardening is the method of chemical-thermal treatment in an electrolyte plasma, which makes it possible to intensify the saturation process. Reducing the duration of the saturation process is one of the important directions for the further development of this process. As is known, nitriding is the most common process of chemical-thermal treatment, which makes it possible to increase the tool life of high-speed steels. At present, a large number of technological processes of nitriding based on liquid nitriding in cyanide baths, gas nitriding and ion-plasma nitriding have been developed. However, despite the many advantages of these processes, they have significant drawbacks - a long process time, high cost and environmental hazard. Since nitriding consumes a large amount of energy and technological materials, and in many cases ammonia is used as a saturating medium, which is harmful to the environment. Therefore, it is advisable to use the electrolytic-plasma method for nitriding tools made of high-speed steels, which makes it possible to intensify the process of surface saturation, reduce processing time, reduce energy costs, improve the environmental performance of the process and reduce the consumption of the saturating medium.

Recently, quite intensive research has been carried out on the effect of electrolytic-plasma treatment on the structure and properties of steels and alloys, work is underway to develop and implement an electrolytic-plasma heating process for surface treatment, in particular, surface chemical-thermal treatment of various products. At the same time, research in this direction is limited to surface carburizing, nitrocarburizing, boriding, sulfiding, and nitriding of low-carbon and low-alloyed structural steels, carbon tool steels, and stainless steels. Literature analysis showed that there is no information about the chemical-thermal treatment of high-speed steels in an electrolyte plasma. This may be due to the laboriousness of electrolytic plasma treatment at relatively low temperatures, which does not allow the use of this method as a finishing treatment, which is an important condition for some alloyed steels, in particular, for high-speed steels. In addition, there is very little information about the structural-phase states and tribological characteristics of steels nitrided in electrolytic plasma, as well as about the physical processes that determine the formation of the composition, structure, and properties of the nitrided layer during electrolytic-plasma nitriding. Moreover, the experimental data are not sufficiently systematized in the literature and are often very contradictory. It should also be noted the insufficient level of development of the metallurgical approach to the tribological properties of nitrided steels, structural criteria responsible for the tribological characteristics of nitrided steels, which hinders the possibility of a reasonable choice of processing technology and the full implementation of the existing hidden reserves of this effective method of chemical-thermal treatment.