Fatigue strength of Co–Cr–Mo alloy clasps prepared by selective laser melting. (June 2016)

• Record Type: Journal Article
• Authors: Kajima, Yuka; Takaichi, Atsushi; Nakamoto, Takayuki; Kimura, Takahiro; Yogo, Yoshiaki; Ashida, Maki; Doi, Hisashi; Nomura, Naoyuki; Takahashi, Hidekazu; Hanawa, Takao; Wakabayashi, Noriyuki
• Is Part Of: Journal of the mechanical behavior of biomedical materials. Volume 59(2016)
• Page Start: 446
• Page End: 458
• Publication Date: 2016-06
• Subjects: Selective laser melting -- Anisotropy -- Fatigue strength -- Removable partial denture -- Clasp -- Co–Cr–Mo alloy; Biomedical materials -- Periodicals; Biomedical materials -- Mechanical properties -- Periodicals; Biomedical materials; Biomedical materials -- Mechanical properties; Periodicals; Electronic journals; 610.28
• DOI: 10.1016/j.jmbbm.2016.02.032
• Languages: English
• ISSNs: 1751-6161

Abstract

Abstract: We aimed to investigate the fatigue strength of Co–Cr–Mo clasps for removable partial dentures prepared by selective laser melting (SLM). The Co–Cr–Mo alloy specimens for tensile tests (dumbbell specimens) and fatigue tests (clasp specimens) were prepared by SLM with varying angles between the building and longitudinal directions (i.e., 0° (TL0, FL0), 45° (TL45, FL45), and 90° (TL90, FL90)). The clasp specimens were subjected to cyclic deformations of 0.25 mm and 0.50 mm for 10 6 cycles. The SLM specimens showed no obvious mechanical anisotropy in tensile tests and exhibited significantly higher yield strength and ultimate tensile strength than the cast specimens under all conditions. In contrast, a high degree of anisotropy in fatigue performance associated with the build orientation was found. For specimens under the 0.50 mm deflection, FL90 exhibited significantly longer fatigue life (205, 418 cycles) than the cast specimens (112, 770 cycles). In contrast, the fatigue lives of FL0 (28, 484 cycles) and FL45 (43, 465 cycles) were significantly shorter. The surface roughnesses of FL0 and FL45 were considerably higher than those of the cast specimens, whereas there were no significant differences between FL90 and the cast specimens. Electron backscatter diffraction (EBSD) analysis indicated the grains of FL0 showed preferential close to <001> orientation of the γ phase along the normal direction to the fracture surface. In contrast, the FL45 and FL90 grains showed no significant preferential orientation. Fatigue strength may therefore be affected by a number of factors, including surface roughness and crystal orientation. The SLM process is a promising candidate for preparing tough removable partial denture frameworks, as long as the appropriate build direction is adopted. Graphical abstract: Highlights: Co–Cr–Mo alloy clasps were prepared by selective laser melting (SLM). The fatigue strength of the alloy clasps was investigated. Anisotropy in fatigue life was associated with building direction. The highest fatigue strength was significantly higher than for the cast specimens. Anisotropy should be considered when designing the metal frameworks using SLM.