20.500.12556/RUL-141260 Vpliv pogojev vakuumske cementacije na mehanske lastnosti jekla 16MnCrS5 in obremenitev okolja diplomsko delo Effect of vacuum carburizing conditions on mechanical properties of 16MnCrS5 steel and environmental impact diploma work Vakuumska cementacija je kemotermični postopek, ki sestoji iz procesov naogljičenja v vakuumu in toplotne obdelave. S postopkom vakuumske cementacije povišamo trdoto jekla na površini, s čimer izboljšamo obrabno obstojnost in povečamo trajno dinamično trdnost. V primerjavi s konvencionalnimi metodami naogljičenja, kjer se uporabljajo temperature naogljičenja med 900 in 950 °C, odsotnost kisika v vakuumski peči omogoča naogljičenje pri temperaturah ki segajo vse do 1050 °C. Namen diplomske naloge je bil analiza mikrostrukture ter mehanskih lastnosti jekla 16MnCrS5 po vakuumski cementaciji. Temperatura naogljičenja je bila 1020 °C, temu pa je sledilo kaljenje v plinu N2. Po vakuumski cementaciji smo z namenom zmanjšanja velikosti kristalnih zrn jeklo ponovno kalili v olju s temperature 850 °C. V okviru diplomske naloge smo preučili vpliv višje temperature naogljičenja v vakuumski peči na mehanske lastnosti jekla, mikrostrukturo in določili obremenitev procesa na okolje. Po vakuumski cementaciji in ponovnem kaljenju vakuumsko cementiranega jekla smo mehanske lastnosti primerjali z referenčnim vzorcem iz kaljenega jekla. Ugotovili smo, da s ponovnim kaljenjem jekla po vakuumski cementaciji izboljšamo njegovo napetost tečenja in natezno trdnost. Po vakuumski cementaciji je bila napetost tečenja 433 MPa in natezna trdnost 748 MPa, po ponovnem kaljenju pa se je napetost tečenja povečala na 589 MPa in natezna trdnost na 943 MPa. V primerjavi s kaljenim referenčnim vzorcem, pri katerem je napetost tečenja znašala 499 MPa in natezna trdnost 939 MPa, so se mehanske lastnosti po vakuumski cementaciji nekoliko znižale, vendar smo jih s ponovnim kaljenjem izboljšali. S ponovnim kaljenjem se je povečala tudi globina cementacije, in sicer iz 1,81 mm na 2,79 mm. Zaradi draginje na trgu energentov in želje po zmanjšanju obremenitve na okolje, smo proučili tudi vpliv postopkov na okolje in stroške. Primerjali smo vakuumsko cementacijo, ponovno kaljenje cementiranega jekla v kalilni peči in plinsko cementacijo v kalilni peči, ki je že uveljavljen proces. Vakuumska cementacija in ponovno kaljenje po vakuumski cementaciji imata v primerjavi s plinsko cementacijo pozitiven vpliv na okolje, saj ogljični odtis zmanjšamo za 79 %. Vacuum carburization is a chemical-termical process, that consists of carburization in vacuum, followed by heat treatment. With a process of vacuum carburization surface hardness that improves wear resistance, and dynamic strength are increased. In comparison to conventional carburiziation methods, where temperatures ranging from 900 to 950 °C are used, the absence of oxygen allows for higher carburizing temperatures of up to 1050 °C. The aim of the thesis was to analyze the microstructure and mechanical properties of 16MnCrS5 steel after vacuum carburization. The carburizing was performed at 1020 °C, followed by quenching in N2 gas. After vacuum carburization, in order to reduce the size of the crystal grains, the steel was quenched again in oil at a temperature of 850 °C. In diploma work, the effect of elevated carburizing temperatures in vacuum furnace on mechanical properties of steel, microstructure, and environmental impact was studied. After vacuum cementation and oil quenching of the vacuum carburized steel, the mechanical properties were compared with a reference sample made of hardened steel. We found that oil quenching after vacuum carburizing process improved yield strength and tensile strength. Yield strength after vacuum carburizing was 433 MPa and tensile strength 748 MPa, while after oil quenching yield strength (589 MPa) and tensile strength (943 MPa) were both increased. Compared to quenched reference sample, which had a yield stress of 499 MPa and a tensile strength of 939 MPa, the mechanical properties after vacuum carburization decreased slightly, but were improved by additonal quenching. With oil quenching carburized case depth also increased, from 1,812 mm to 2,788 mm. Due to increasing prices in the energy source market and our wish to lower the impact on the environment, the effects of processes on the environment and cost were also studied. Three processes, which were vacuum carburization, oil quenching of vacuum carburized specimens in a quenching furnace, and already established gas carburization in a quenching furnace, were compared. Vacuum carburization and repeated quenching after vacuum carburization have shown a lower rate of harmful environmental effects compared to gas carburizing, where the released CO2 amount was higher by 79 %. jeklo 16MnCrS5 vakuumska cementacija mikrostukturna analiza mehanske lastnosti ogljični odtis 16MnCrS5 steel vacuum carburization microstructural analysis mechanical properties carbon footprint true false false [G. Krek] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2022-09-27 09:00:19 2022-09-27 09:00:26 2022-11-29 13:23:40 0000-00-00 00:00:00 2022 0 Ljubljana 0 Ljubljana XIII, 55 f. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 669 88487 131508483 12764.pdf 12764.pdf 1 81E55FFC4C3BF21960FCC63D5F8E434E 45e03593cb16935e0dfa7279b425af9c387b2ea8cabe7d1b3e3ad3ea92c5f77a 0f1ceb4e-3e32-11ed-9c94-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=162230 Naravoslovnotehniška fakulteta 0 0 0