Abstract
The objective of this study was to investigate the effect of laser beam parameters on the mechanical and physical properties of cast commercially pure titanium. Dumbbell-shaped test specimens (ISO6871) were cast with ASTM grades 2 and 3 Ti. The cast surfaces were laser-treated with various laser emission parameters (current: 200, 220, and 240 A; spot diameter: 1.0, 1.6 mm; pulse duration: 10, 1 ms) under argon shielding. Tensile testing was conducted at a crosshead speed of 1.0 mm/min. Data of tensile strength and elongation were statistically analyzed using ANOVA/Tukey’s test (α=0.05). Hardness depth profiles were made with cross sections of rod-shaped specimens after laser treatments. Control specimens without laser treatment were also prepared. The laser-treated specimens showed significantly higher tensile strengths than those of control specimen for both grades 2 and 3 Ti. The specimens treated with 1.0 mm spot diameter indicated higher tensile strengths than those treated with 1.6 mm spot diameter for both currents (200 A and 240 A). The laser treatment decreased the subsurface hardness and increased the hardness between 75 μm and 400 μm in depth when compared to the hardness of control specimens. Laser surface treatment for cast commercially pure titanium modified integrity of cast surface and significantly improved mechanical and physical property.
Highlights
Pure (CP) titanium and its alloys have been widely applied for orthopedic and dental implants because of their excellent biocompatibility [1,2,3], high corrosion resistance [4, 5], inherent ability to osseointegrate, and low modulus of elasticity (Young’s modulus) to more closely match to the elastic modulus of the bone [3, 6, 7]
The Commercially pure (CP)-Ti was cast with a magnesia-based investment material
Tensile strengths and elongations of control specimens and the specimens lasertreated with various parameters for laser emission are presented in Figure 3 through Figure 6
Summary
Pure (CP) titanium and its alloys have been widely applied for orthopedic and dental implants because of their excellent biocompatibility [1,2,3], high corrosion resistance [4, 5], inherent ability to osseointegrate, and low modulus of elasticity (Young’s modulus) to more closely match to the elastic modulus of the bone [3, 6, 7]. Even if the grade 4 pure titanium possesses highest strength and hardness, its strength and hardness are lower than those of titanium alloys, in which alloying elements modify microstructures resulting in improvement of their mechanical and physical properties. Since titanium has extremely high affinity with oxygen at high temperature, cast titanium surfaces are usually contaminated with refractory oxide contained in the investment material during casting. The contaminated surface layers reduce the integrity of cast surface and induce hard and brittle cast surfaces which lead to decrease in mechanical properties [16], fatigue [17], and wear resistances [18]
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