In this work are discussed some experimental data about the obtaining of recast layers on the surface of high speed tool steel after electrical discharge treatment in electrolyte. The electrical discharge treatment of steel surface in electrolyte produces a recast layer with specific combination of structure characteristics in result of nonequilibrium phase transformations. The modification goes by a high energy thermal process in electrical discharges on a very small area on the metallic surface involving melting, alloying and high speed cooling in the electrolyte. Obtained recast layers have a different structure in comparison with the metal matrix and are with higher hardness, wear- and corrosion resistance.
Author: Krastev D.
INFLUENCE OF NANOSIZED SILICON NITRIDE ADDITION DURING CASTING ON THE MICROSTRUCTURE OF X210Cr12 STEEL
The objective of this study is to investigate the effect of modification and nitrogen alloying of X210Cr12 tool steel by addition of nanosized Si N during the casting process. This is an air hardening, high-carbon, high-chromium tool steel which displays an excellent 3 4 wear resistance and has good dimensional stability and high compressive strength. Of great importance for the tools fabrication of this steel is the ledeboritic structure after casting and the influence of its characteristics on the next processes of forging. machining and heat treatment for obtaining of optimal properties. In this case a modification at the cast process and obtaining of finer structure is a precondition for better results on the next stages of tool manufacture. The role of nitrogen for obtaining of fine grained structure is already proved for many types of steels and the alloying process is precise developed. Si N is one of the most suitable nitrogenous alloying agents 3 4 for production of alloyed with nitrogen steels because of its high nitrogen content and stability. The investigations show a considerable improvement of the cast structure of X210Cr12 tool steel after the addition of small amount of nanosized silicon nitride during the casting process.