20.500.12556/RUL-188727 Kemotermično utrjevanje površine jekla 25CrMo4 Thermochemical surface hardening treatment of 25CrMo4 steel V diplomskem delu je bil raziskan vpliv treh postopkov kemotermičnega površinskega utrjevanja na jeklo 25CrMo4, in sicer cementacije, plazemskega nitridiranja in karbonitridiranja. Namen raziskave je bil primerjati njihov vpliv na trdoto, globino utrjenih plasti, globino površinsko spremenjenih območij, porazdelitev ogljika in dušika ter nastalo mikrostrukturo. Za eksperimentalno delo je bilo pripravljenih šest vzorcev, po dva za vsak postopek. Po kemotermični obdelavi so bile izvedene meritve trdote po Vickersu pri obremenitvi 0,5 kgf, metalografske preiskave, preiskave z vrstičnim elektronskim mikroskopom (SEM) ter energijsko disperzijske spektroskopske analize (EDS). Iz profilov trdote so bile določene globine utrjenih plasti, na prečnih prerezih pa so bile metalografsko ocenjene globine površinsko spremenjenih območij. Največja izmerjena trdota cementiranega vzorca je znašala 692 HV, plazemsko nitridiranega 730 HV in karbonitridiranega 754 HV. Globina utrjene plasti, določena iz profila trdote, je pri cementiranem vzorcu znašala približno 0,57 mm in pri karbonitridiranem približno 0,42 mm; globina nitridirane plasti pa približno 0,42 mm. Metalografsko ocenjene globine površinsko spremenjenih območij so znašale približ-no 0,31 mm pri cementaciji; 0,23 mm pri plazemskem nitridiranju in 0,44 mm pri karbonitridiranju. Energijsko disperzijske spektroskopske analize so pokazale obogatitev območja ob površini z ogljikom pri cementaciji, z dušikom pri nitridiranju ter z ogljikom in dušikom pri karbonitridiranju. Mikrostrukturne preiskave so pri cementiranem in karbonitridiranem vzorcu pokazale pretežno nizkotemperaturno popuščeno martenzitno mikrostrukturo na površini ter mešano mikrostrukturo v je-dru, medtem ko je nitridirani vzorec v jedru ohranil feritno-perlitno mikrostrukturo.Ugotovljeno je bilo, da so vsi trije postopki povečali trdoto površinskega območja. Pri uporabljenih procesnih pogojih je karbonitridiranje zagotovilo največjo izmerjeno trdoto, plazemsko nitridiranje pa najmanjšo spremembo lastnosti jedra. The effects of carburizing, plasma nitriding and carbonitriding on 25CrMo4 steel were investigated. The aim was to compare their effects on hardness, the depth of harde-ned layers, the depth of surface-modified regions, the distribution of carbon and ni-trogen, and the resulting microstructure. Six specimens were prepared, with two used for each treatment. After thermochemical treatment, Vickers hardness mea-surements at a load of 0.5 kgf, metallographic examinations, scanning electron mic-roscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were car-ried out. The depths of hardened layers were determined from hardness profiles, while the depths of surface-modified regions were estimated metallographically on cross-sections. The maximum measured hardness was 692 HV for the carburized specimen, 730 HV for the plasma-nitrided specimen and 754 HV for the carbonitrided specimen. The hardened layer depth was approximately 0.57 mm for the carburized specimen and 0.42 mm for the carbonitrided specimen, while the nitriding hardness depth was approximately 0.42 mm. The metallographically estimated depths of the surface-modified regions were approximately 0.31 mm after carburizing, 0.23 mm after plasma nitriding and 0.44 mm after carbonitriding. Energy-dispersive X-ray spectroscopy analyses showed enrichment of the near-surface region with carbon after carburizing, with nitrogen after nitriding, and with both carbon and nitrogen after carbonitriding. Microstructural examinations of the carburized and carbonitrided specimens showed a predominantly low-temperature tempered martensitic microstructure at the surface and a mixed microstructure in the core, whereas the nitrided specimen retained a ferritic-pearlitic microstructure in the core. All three processes increased surface-region hardness. Under the applied processing conditions, carbonitriding produced the highest measured hardness, whereas plasma nitriding caused the least change in the properties of the core. jeklo 25CrMo4 kemotermično površinsko utrjevanje cementacija plazemsko nitridiranje karbonitridiranje trdota 25CrMo4 steel thermochemical surface hardening carburizing plasma nitriding carbonitriding hardness true false false Slovenski jezik Angleški jezik Diplomsko delo/naloga 2026-09-26 09:00:34 2026-09-26 09:00:38 2026-09-27 04:19:14 0000-00-00 00:00:00 2026 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 1970-01-01 117921 31647.pdf 31647.pdf 1 EE5DE0D0031ABEA1F0563AA95BE762AB 2bc4feaecb8e27650067e544dd8737e801f74f3343d37daebc3caac4f4382fd7 e45f67e7-b977-11f1-8bc5-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=249051 Naravoslovnotehniška fakulteta 0 0 0