Selective laser melting and sintering technique of the cobalt-chromium dental alloy

Abstract

Introduction/Objective the objective of this paper is to describe the microstructure and mechanical properties of sintered Co-Cr alloy and to emphasize its advantages and disadvantages with respect to the microstructure and mechanical properties of cast Co-Cr alloy. Methods Base Co-Cr alloy, EOSint M EOS Co-Cr SP2 (EOS GmbH, Munch, Germany), was used for the purpose of this research as the base material for sintering metal structures of metal-ceramic restorations. Metal sintering was conducted by using EOSint M 280 device of German origin in a stream of neutral gas - argon. After that, the alloy was heated over a period of 20 minutes at the temperature of 800°C. The chemical composition of the alloy was determined by energy dispersive spectroscopy. Microstructure of the tested alloy samples was examined under an optical metallographic and scanning electron microscope. Physical and mechanical properties were measured in a universal testing machine. The samples were prepared according to the standard ISO 527-1:1993. Results Chemical composition of the sintered Co-Cr alloy, determined by applying energy dispersive spectroscopy, indicated the same qualitative but different quantitative composition compared to cast Co-Cr alloys. The microstructure of the sintered Co-Cr alloy is lamellar in nature, with two dominant phases: ξ-Co and/or ξ-Cr (fcc - face-centered cubic) and γ-Co (hcp - hexagonal close-packed). Mechanical properties of the Co-Cr alloy obtained by applying selective laser melting technology compared to the cast Co-Cr alloy are superior or approximately the same. Conclusion Selective laser melting of the Co-Cr alloy is a good example of new technologies based on digitization. Together with other digitized procedures, this technology is an introduction to a new era in dentistry popularly called Dentistry 4.0. The advantages of the selective laser melting technology with respect to the conventional technology of casting Co-Cr alloy metal structures are precise metal structure fitting and eco-friendly technology.

Uvod/Cilj Cilj rada je opisati mikrostrukturu i mehaničke karakteristike sinterovane legure Co-Cr i istaći njene prednosti i mane u odnosu na mikrostrukturu i mehaničke karakteristike livene legure Co-Cr. Metode U istraživanju je korišćena bazna legura Co-Cr, Eosint M EOS Co-Cr SP2 (EOS GmbH, Minhen, Nemačka) za sinterovanje metalnih konstrukcija metalokeramičkih nadoknada. Sinterovanje metala je obavljeno na aparatu EOSint M 280 u struji neutralnog gasa argona. Nakon toga legura je žarena 20 minuta na temperaturi od 800° C. Hemijski sastav legure određivan je energodisperzivnom spektroskopijom. Mikrostruktura ispitivanih uzoraka legure posmatrana je na optičkom metalografskom i elektronskom skenirajućem mikroskopu. Fizičko-mehaničke karakteristike merene su na univerzalnoj kidalici. Uzorci su pripremani prema standardu ISO 527-1:1993. Rezultati Hemijski sastav uzoraka sinterovane legure CoCr pokazao je isti kvalitativan ali različit kvantitativan sastav u odnosu na legure Co-Cr za livenje. Mikrostruktura sinterovane legure Co-Cr je lamelarne prirode, u kojoj dominiraju dve faze: e-Co i/ili e-Cr (fcc - face-centred cubic) i g-Co (hcp - hexagonal close-packed). U poređenju sa livenom legurom Co-Cr, mehaničke karakteristike sinterovane legure Co-Cr su bolje ili približno iste. Zaključak Selektivno lasersko topljenje legure Co-Cr je dobar primer novih tehnologija zasnovanih na digitalizaciji. Zajedno sa drugim digitalizovanim procedurama koje prethode, ova tehnologija je predvorje novoj eri u stomatologiji, popularno nazvanoj Dentistry 4.0. Prednosti tehnologije selektivnog laserskog topljenja u odnosu na tehnologiju konvencionalnog livenja metalnih konstrukcija od legure Co-Cr su preciznost naleganja metalne konstrukcije i čista tehnologija.