Laser Surface Texturing of Co–Cr–Mo Alloy for Biomedical Applications:A Case Study for the Effects of Process Parameters on Surface Properties

This study presents a comprehensive approach to applying texturing processes created by engraving on the surface of CoCr28Mo alloy workpieces using a 20 W pulsed nanosecond fiber laser.The hatch strategy and distance,frequency,and scan speed were control parameters for texturing applications.The effectiveness of the parameters in terms of roughness and contact angle of the texturized surface was investigated.Surface roughness and contact angle were analyzed using variance analysis to identify each variable's influence.It has been determined that the roughness of the texture defined by the hatch strategy plays a decisive role in the wettability behavior of the surface;however,the scan speed,frequency,and hatch distance which are among the laser surface texturing conditions are influential in the roughness and contact angle.Increasing scan speed and hatch distance while decreasing frequency resulted in smoother surfaces,increasing the contact angle.Textures having rough surfaces produced with different processing conditions exhibit a super hydrophilic behavior.The contact angle is most sensitive to the hatch distance;however,the frequency has the least influence on the contact angle.The most and least efficient surface roughness parameters are revealed to be scan speed and hatch distance,respectively.

Effect of thermomechanical treatment on the mechanical and microstructural evolution of a β-type Ti-40.7Zr–24.8Nb alloy

In this study,the microstructural evolution and mechanical properties of a newly developed Ti-40.7Zr-24.8Nb(TZN)alloy after different thermomechanical processes were examined.As-cast TZN alloy plates were solutiontreated at 890℃ for 1 h,after which the thickness of the alloy plates was reduced by cold rolling at reduction ratios of 20%,56%,76%,and 86%.Stress-induced α”formation,{332}<113>β mechanical twinning,and kink band formation were observed in the cold-rolled TZN alloy samples.In the TZN sample after cold rolling at the 86%reduction ratio plus a recrystallization annealing at 890℃ for 1 h,the deformation products of a stressinducedα”phase,{332}<113>β mechanical twinning,and kink bands disappeared,resulting in a fine,equiaxed singleβ phase.The alloy samples exhibited elongation at rupture ranging from 7%to 20%,Young's modulus ranging from 63 to 72 GPa and tensile strength ranging from 753 to 1158 MPa.The TZN alloy sample after cold rolling and recrystallization annealing showed a yield strength of 803 MPa,a tensile strength of 848 MPa,an elongation at rupture of 20%,and an elastic admissible strain of 1.22%,along with the most ductile fractures during tensile testing.