18 KB738 KB18 KB200020242004Čmakal, JosefHnilica, FrantišekJurči, Peterletnik:38številka:55 stranistr. 263-267ISSN:1580-2949COBISSID:362922URN:URN:NBN:SI:doc-9VNTVS49enInštitut za kovinske materiale in tehnologijeMateriali in tehnologijeledeburitna jeklanitriranje v plazmirazpokežilavostChanges to the fracture behaviour of the Cr-V ledeburitic steel vanadis 6 as a result of plasma nitriding|Three-point test specimens made from VANADIS 6 ledeburitic steel were heat treated using two basic regimes to produce different hardness values. The cross-sections of the specimens ranged between (10x10) mm and (1x10) mm - this range was chosen in order to evaluate the influence of the portion of nitrided material on the fracture toughness. The plasma nitriding was carried out for various combinations of temperature and dwell time. The testing of the fracture toughness with static three-point bending established the dominant role of the presence of the nitrided layer on both the bending strength and the fracture mechanism. Only if the material was not plasma nitrided was the role of the austenitizing temperature clearly shown - the higher the temperature, the worse the three-point bending strength. The character of the initiation and propagation of the fracture was low-energy ductile when the material was hardened and tempered. The presence of the plasma-nitrided region on the surface changed the initiation as well as the propagation mechanism to that of cleavage. The thickness of the cleavage region increased as the nitrided region became thicker, which induced an additional lowering of the bending strengthŽilavostni vzorci, izdelani iz ledeburitnega jekla vANADIS 6 so bili toplotno obdelani po dveh režimih, ki sta zagotovila različno trdoto. prerez vzorcev je bil razvrščen v področja od (10 x 10) mm do (1 x 10) mm, da bi ugotovili vpliv deleža nitriranega materiala na lomno žilavost. Nitriranje v plazmi je bilo izvršeno pri različnih kombinacijah temperature in časa nitriranja. Preizkus lomne žilavosti z metodo tri točkovnega upogibanja je pokazal prevladujoč vpliv prisotnosti nitrirane plasti na upogibno trdnost in mehanizem preloma. Samo pri materialu, ki ni bil nitriran v plazmi, se je pokazal vpliv temperature avstenitizacije - čim višja je bila temperatura, tem nižja je bila upogibna trdnost. Ko je bil material kaljen in popuščan, je bila iniciacija in propagacija razpoke značilno nizkoenergijska, duktilna. Prisotnost področja, nitriranega v plazmi, na površini, je spremenila iniciacijo kot tudi mehanizem propagacije, ki je postal cepilen. Debelina cepilnega področja narašča z naraščanjem debeline nitriranega področja, to pa povzroči dodatno zmanjšanje upogibne trdnostiTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije