Study of Optical Properties of Surface Layers Produced by Laser Surface Melting and Laser Surface Nitriding of Titanium Alloy.

Aleksander Lisiecki

doi:10.3390/ma12193112

Abstract

This study measured optical properties, such as specular, diffuse, and total reflection for 808 nm wavelength, characteristic for high power diode lasers radiation, from the surface of titanium alloy Ti6Al4V at delivery conditions, polished, and oxidized. Moreover, the optical properties of surface layers produced by high power direct diode laser (HPDDL) melting and nitriding were determined. Additionally, a methodology for determining the value of absorption for 808 nm wavelength of the HPDDL radiation on the surface of a melt pool during laser surface melting and nitriding of titanium alloy was proposed. The results show that the distinct differences in absorption affect the heat transfer, thermal conditions of laser heating and thereby the penetration depth during laser melting and nitriding of the titanium alloy.

Highlights

Titanium alloys have excellent mechanical properties, but during the manufacture of machinery parts, components or tools it is often necessary to apply additional surface treatments to improve the tribological characteristic of working surfaces [1,2,3,4,5,6,7,8,9,10,11]
The author attempts to determine optical properties such as emissivity, reflectivity, and absorption of surface layers produced on the substrate of titanium alloy Ti6Al4V by laser surface melting and nitriding using the high power direct diode laser emitting radiation with a wavelength of
The aim of the first stage of the study was to determine and compare the optical properties of the titanium alloy Ti6Al4V (Grade 5 according to the standard ASTM B 265-99) with different surface conditions, as well as the surface layers produced by laser melting the titanium alloy in an argon atmosphere, and laser nitriding in a gaseous nitrogen atmosphere

Summary

Introduction

Titanium alloys have excellent mechanical properties, but during the manufacture of machinery parts, components or tools it is often necessary to apply additional surface treatments to improve the tribological characteristic of working surfaces [1,2,3,4,5,6,7,8,9,10,11]. Laser gas nitriding is a very efficient and flexible method for shaping the surface characteristics of commercially pure titanium and technical titanium alloys [1,2,3,4,5,6,7,8,9,10,11] This is because of the large chemical affinity of titanium for nitrogen at elevated temperatures, in a liquid state. The author attempts to determine optical properties such as emissivity, reflectivity, and absorption of surface layers produced on the substrate of titanium alloy Ti6Al4V by laser surface melting and nitriding using the high power direct diode laser emitting radiation with a wavelength of. The author attempts to estimate the absorption coefficients of the metal surface in a liquid state during laser melting of titanium alloy Ti6Al4V in a pure argon atmosphere and in a pure nitrogen atmosphere

Materials and Methods

Results and Discussion

Conclusions