Energy-saving and environmentally safe technology of urea-based carbonitration of high-speed steels in salt baths

Purpose. A study was conducted on the cyanidation of R6M5 high-speed steel using baths composed of urea and sodium carbonate within the temperature range of 550–580°C. Methods. The microstructure of the diffusion layer of steels was studied on cross sections using a Quanta FEG-650 scanning electron microscope equipped with an EBCD microanalysis system with a focused ion beam. This technique allowed for detailed visualization and analysis of the phase composition and morphology of the surface layers. To evaluate the performance characteristics of the cyanidized samples, wear tests were performed under conditions simulating friction during cutting tool operation. Testing was performed to establish a correlation between microstructural features of the diffusion layer and its resistance to abrasive action. Results. The conducted experiments confirmed the significant efficiency of the new salt bath composition for cyanidation of high-speed steel P6M5 under the given temperature conditions. In the process of treatment, modified layers enriched with ε-phases (solid inclusions) are formed on the surface of the material, which provide unique performance characteristics: increased microhardness, reduced friction coefficient and resistance to wear. Conclusion. The possibility of using cyanide-free salt baths for low-temperature cyanidation of P6M5 steel has been established, which expands the technological possibilities of tool production. The combination of high wear resistance and hardness of the treated steel makes the method promising for manufacturing of cutting tools and parts operating under intensive loads. The results of the study demonstrate that the use of the developed composition allows not only to improve the quality of cyanided layers, but also to introduce resource-saving technologies in industry, while maintaining high standards of environmental safety.