Modificação de propriedades superficiais do aço AISI M2 por processo de nitretação a plasma aplicado em ferramenta de corte do tipo fresa

Abstract

The continued use of cutting tools in the metallurgical industries has increased as a result of the continuing need to increase productivity, as disadvantages as wear and tool change costs have followed the same logic of increase. In search of improvements, economic viability and technology, materials engineering seeks several alternatives to improve cutting tools for machining and consequently increase the quantity and quality of parts manufactured in continuous production processes. One such alternative is plasma nitriding commonly used in deforming, drilling, cutting and stamping metal components in order to increase the life of cutting tools. In this way the objective of this work was to use plasma nitriding, which is a clean thermochemical treatment process, as an alternative to raise the surface hardness of a cutting tool of the milling type, resulting in increased tool life and wear resistance and fatigue. With this, samples of the M2 fast steel were obtained from top mills of 10 mm diameter with 4 cutting faces, and submitted to the plasma nitriding process both the samples and cutting tools, using different temperature values (400 ° C, 450 ° C and 500 ° C) in atmospheres with different percentages of nitrogen and hydrogen for a defined time of four hours. For the characterization and qualification of the results were analyzed by surface microhardness to which the superficial hardness of the diffused layer of nitrites was verified on the samples, optical microscopy where the measurement of the thickness of the nitrided layer and wear of the cutting tools in milling machine for a defined time of 60 min. The hardness of the commercial M2 fast steel is 745 HV and the hardnesses obtained after the thermochemical treatment at the temperatures of 400, 450 and 500øC were 1470, 1418 and 1130 HV, respectively. Microscopy revealed that the largest diffusion zone occurred in the process at 500 ° C. When applied in a universal milling machine, the tool nitrided at 400 ° C showed the least wear on the cutting edges. Therefore, the best treatment for application in M2 fast-cut milling cutters is at 400 ° C.