Formation of a Pseudo-periodic Microstructure on Titanium Surfaces Under Pulsed Nanosecond Fibre Laser Irradiation: Topographical and Mechanical Properties
N. Rasti, E. Toyserkani and F. Ismail
This article presents a study of the formation of pseudo-periodic microstructures on titanium surfaces upon irradiation of a single-mode pulsed nanosecond ytterbium fibre laser. It investigates the effect of short 100 ns pulsed laser beam properties including laser power, laser frequency, beam polarization, angle of incidence, and scanning speed on the formation of pseudo-periodic microstructures. The associated process parameters are grouped into two representing quantities: laser intensity and effective energy. The study demonstrates the effect of these two quantities on the surface topography (shape, periodicity, and roughness), heat affected zone (HAZ), chemical composition (oxidation and titanium phase transformation) and mechanical properties (hardness) of the modified surface. It is shown that the microstructures initiation is not possible until laser intensity reaches a certain value close to the damage threshold of the material. After the microstructures are initiated, the laser intensity may remain constant and the growth of structures is mainly controlled by the effective energy.
Keywords: Fibre laser, pseudo-periodic microstructures, titanium, laser microfabrication, nanosecond pulse