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

Abstract

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 σFS /σUTS was ~0.4. These superior mechanical properties were attributed to the fine 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. σFS/σUTS 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.