Characterization of MARAGING steel additively manufactured by selective laser melting

Ovaj diplomski rad sastoji se od teorijskog i eksperimentalnog dijela. U teorijskom dijelu opisani su alatni čelici, njihova mikrostruktura, svojstva te podjela. Detaljnije su opisani alatni čelici za topli rad i MARAGING čelici. Dan je kratak pregled konvencionalnih postupaka proizvodnje, a zatim je detaljnije opisano selektivno lasersko taljenje ili SLM postupak proizvodnje koji spada u aditivne tehnologije. Ovim se postupkom izravno proizvode prototipi, alati i funkcionalni dijelovi, a za njihovu proizvodnju se koristi laserska zraka visokog intenziteta koja tali i spaja čestice metalnog praha. SLM postupkom moguće je proizvesti geometrijski vrlo zahtjevne dijelove skoro 100 %-tne gustoće čija su mehanička svojstva usporedna konvencionalno proizvedenim dijelovima. U eksperimentalnom dijelu napravljeni su uzorci od MARAGING 300 alatnog čelika SLM postupkom s dvije različite debljine sloja taljenja praha laserskim snopom. Na ispitnim uzorcima provedena je toplinska obrada dozrijevanja (precipitacije) sa i bez rastvornog žarenja te je pomoću svjetlosnog mikroskopa ispitana mikrostruktura, a također je ispitana i mikrotvrdoća uzoraka.This thesis consists of a theoretical and an experimental part. The theoretical part describes tool steels, their microstructure, properties and calssification. Hot work tool steels and maraging steels are described in more detail. A brief overview of conventional production processes for tool steels is given, followed by a more detailed description of Selective Laser Melting (SLM) production process, which belongs to additive technologies. With this process, prototypes, tools, and functional parts are directly produced via high-intensity laser beam which melts and connects particles of metal powder. By SLM process it is possible to produce geometrically complex parts of almost 100 % density whose mechanical properties are comparable to conventionally produced parts. In the experimental part, samples were made of MARAGING 300 tool steel by SLM process with two different depths of powder bed melting. One set of samples was heat treated by direct aging and another set was heat treated by solution treatement and then aging. Heat treated samples were comapred to the as-built samples by analysing microstructure and microhardness