title: Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting.
abstract: OBJECTIVE
  CrCoMo alloy specimens were successfully fabricated using selective laser melting (SLM). The aim of this study was to carefully investigate microstructure of the SLM specimens in order to understand the influence of their structural features inter-grown on different length scales ranging from nano- to macro-levels on their mechanical properties.
  
  
  METHODS
  Two different sets of processing parameters developed for building the inner part (core) and the surface (skin) of dental prostheses were tested. Microstructures were characterized by SEM, EBSD and XRD analysis. The elemental distribution was assessed by EDS line profile analysis under TEM. The mechanical properties of the specimens were measured.
  
  
  RESULTS
  The microstructures of both specimens were characterized showing formation of grains comprised of columnar sub-grains with Mo-enrichment at the sub-grain boundaries. Clusters of columnar sub-grains grew coherently along one common crystallographic direction forming much larger single crystal grains which are intercrossing in different directions forming an overall dendrite-like microstructure. Three types of microstructural defects were occasionally observed; small voids (<10 μm), fine cracks at grain boundaries (<10 μm) and cracks at weld line boundaries (>10 μm). Despite the presence of these defects, the yield and the ultimate tensile strength (UTS) were 870 and 430MPa and 1300MPa and 1160MPa, respectively, for the skin and core specimens which are higher than casted dental alloy.
  
  
  CONCLUSIONS
  Although the formation of microstructural defects is hard to be avoided during the SLM process, the SLM CoCrMo alloys can achieve improved mechanical properties than their casted counterparts, implying they are "defect-tolerant".
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Qian
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Saeidi
authors.affiliation: Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, Kosice, Slovakia.
authors.forename: L
authors.initials: L
authors.lastname: Kvetková
authors.affiliation: Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 916 24 Trnava, Slovak Republic.
authors.forename: F
authors.initials: F
authors.lastname: Lofaj
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Xiao
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden. Electronic address: shen@mmk.su.se.
authors.forename: Z
authors.initials: Z
authors.lastname: Shen
mesh_terms: D002857:Chromium / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry; D006244:Hardness; D006358:Hot Temperature; D007834:Lasers; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008982:Molybdenum / Q000737:chemistry*; D049329:Nanostructures; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D003722:Dental Alloys; D003734:Dental Casting Investment; D002857:Chromium; D003035:Cobalt; D008982:Molybdenum
keywords: Co-Cr-Mo dental alloy; Mechanical properties; Microstructure and defects; SLM