MECHANICAL PROPERTIES OF SURFACE STRUCTURES OF TITANIUM ALLOY VT9 AFTER REPEATED LOCAL PROCESSING WITH NANOSECOND LASER PULSES

Abstract

. Purpose. The regularities of a simultaneous increase in microhardness and plastic properties of the surface of titanium alloy VT9 are investigated. The hardness and Young’s modulus of thin surface layers are determined. Methodology and Approach. The methods employed are based on the use of nanosecond laser pulses initiating a complex of physical and chemical processes. The method of continuous indentation with a maximum load of 0,05 N is used. The mechanical properties of surface structures of titanium alloy VT9 after laser treatment are analyzed. Using the load-penetration diagrams, the following values were calculated: the contact depth of penetration, the stiffness of the contact ‘indenter–material’ pair, the projection area of the unreconstructed print, and the effective Young’s modulus. On the basis of the Oliver–Pharr method, the nano- and microhardness, as well as the modulus of longitudinal elasticity of the surface layers of a titanium alloy are estimated Results . It is found that as a result of processing, the microhardness of the surface increases by 2,5–4,5 times, and the Young’s modulus by 1,1–1,5 times. A distinctive feature of the proposed treatment method is good adhesion of the surface layer with the bulk material, which reduces the probability of high mechanical stresses and cracking. Theoretical and Practical implications . The proposed method of laser processing makes it possible to form hardened surface layers in a normal atmosphere, which contributes to a significant simplification of the technological process and reduces its cost.