Characterization of heat treated and surface hardened steels

Ovim radom obrađena je teme karakterizacije toplinsko i toplinsko-kemijski obrađenih čelika. Sam rad se sastoji od teoretskog i praktičnog dijela, uz koji je obavljena i analiza rezultata dobivenih u praktičnom dijelu. Teoretski dio se sastoji od samog opisa toplinske obrade i njenih parametra, opisa toplinske obrade kaljenjem i važnosti metastabilnog Fe-Fe3C i TTT dijagrama za sami postupak. Objašnjena su svojstva zakaljivosti i prokaljivosti i navedeni i razrađeni ostali postupci toplinske obrade cjelovitog volumena. Također u teoretskom dijelu su opisani postupci obrade površinskim modificiranjem nitriranje, nitrokarburiranje, boriranje i indukcijsko kaljenje. U praktičnom dijelu rada provedena je metalografska priprema toplinski i toplinsko-kemijski obrađenih uzoraka, analiza njihove mikrostrukture pomoću svjetlosnog mikroskopa i mjerenje mikrotvrdoće kaljenih uzoraka čelika s različitim udjelima ugljika. Također je provedena analiza utjecaja ugljika na mikrostrukturu i izmjerenu tvrdoću za uzorke obrađene kaljenjem i iste uzorke u normaliziranom stanju. The topic of this paper is the characterization of heat-treated and thermochemically treated steels. The paper itself consists of a theoretical and a practical part, along with which an analysis of the results obtained in the practical part was also carried out. The theoretical part consists of the description of the heat treatment and its parameters, the description of hardening, and the importance of the metastable Fe-Fe3C and TTT diagram for the procedure itself. Hardenability is defined as the property of steel. Other procedures for heat treatment are listed and elaborated. Also, processes of surface modification, nitriding, nitrocarburizing, boriding, and induction hardening are described. In the practical part of the paper, metallographic preparation of thermally and thermochemically treated samples was done, analysing their microstructures using a microscope and measuring the microhardness of hardened samples with different carbon contents. Finally, an analysis of the influence of carbon content on the microstructure and the measured hardness was also carried out for the hardened samples and the same samples in the normalized state.