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Chemical, Physical, and Mechanical Properties and Microstructures of Laser-Sintered Co–25Cr–5Mo–5W (SP2) and W–Free Co–28Cr–6Mo Alloys for Dental Applications

1
National Institute of Advanced Industrial Science and Technology, 1–1 Higashi 1–chome, Tsukuba, Ibaraki 305–8566, Japan
2
IDS Co., Ltd., 3–5–4 Hongo, Bunkyo–ku, Tokyo 113–0033, Japan
3
Graduate School of Oral Health Sciences, Osaka Dental University, 1–4–4 Makinohonmachi, Hirakata City, Osaka 573–1144, Japan
*
Author to whom correspondence should be addressed.
Materials 2019, 12(24), 4039; https://doi.org/10.3390/ma12244039
Received: 15 November 2019 / Revised: 28 November 2019 / Accepted: 2 December 2019 / Published: 4 December 2019
We examined the chemical, physical, and mechanical properties and microstructures of laser-sintered Co–25Cr–5Mo–5W (SP2) and W–free Co–28Cr–6Mo alloys. The tensile and fatigue properties of the laser-sintered Co–Cr–Mo alloys were extremely superior to those of dental-cast alloys. The ultimate tensile strength (σUTS) and total elongation (T.E.) were close to those of hot-forged Co–28Cr–6Mo alloys. The fatigue strengths (σFS) at 107 cycles of the 90°-, 45°-, and 0°-direction-built Co–28Cr–6Mo alloys were ~500, ~560, and ~600 MPa, respectively. The ratio σFSUTS was ~0.4. These superior mechanical properties were attributed to the fine π-phase particles in the grains and grain boundaries of the fine face–centered cubic (fcc) matrix formed owing to the rapid solidification. The chemical composition of 20-times-laser-sintered Co–Cr–Mo alloy without the virgin powder added was approximately the same as that of the alloy laser-sintered with the virgin powder. σFS of the 90°-direction-built alloys after laser sintering 20 times was also ~500 MPa. σUTS of hot-forged Co–28Cr–6Mo alloys decreased with increasing annealing temperature, whereas T.E. increased. For the Co–Cr–Mo alloys annealed at 1000 to 1150 °C for 30 min after laser sintering, the rates of decrease in σUTS were small. σFSUTS increased to near those of annealed Co–28Cr–6Mo alloys after hot forging. The durability of clasps fabricated by laser sintering was superior to that of dental-cast clasps.
Keywords: cobalt–chromium–molybdenum alloys; laser sintering; microstructure; tensile property; fatigue property; physical property; dental prostheses cobalt–chromium–molybdenum alloys; laser sintering; microstructure; tensile property; fatigue property; physical property; dental prostheses
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MDPI and ACS Style

Okazaki, Y.; Ishino, A.; Higuchi, S. Chemical, Physical, and Mechanical Properties and Microstructures of Laser-Sintered Co–25Cr–5Mo–5W (SP2) and W–Free Co–28Cr–6Mo Alloys for Dental Applications. Materials 2019, 12, 4039.

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