Comparison of Titanium Metal Matrix Composite Surface Layers Produced During Laser Gas Nitriding of Ti6Al4V Alloy by Different Types of Lasers

Abstract

The article presents the results of a comparative study of the nitriding process of titanium alloy substrate using two lasers with different characteristics of laser beams. One of the applied lasers was a high power diode laser emitting at a dominant wavelength of 808 nm, with a rectangular laser beam spot, and multimode energy distribution across the spot. The second laser was a solid state Yb:YAG disk laser emitting at a wavelength of 1.03 µm, with a circular beam spot, characterized by near Gaussian energy distribution across the spot. In a case of both lasers single stringer beads with a similar width and at similar energy input were produced. As a result of melting of the substrate with a laser beam in a pure gaseous nitrogen atmosphere composite surface layers with in situ precipitated titanium nitrides embedded in the metallic matrix of titanium alloy were produced, in both cases. However, the surface topography and structure is different for the surface layers produce by different lasers at the same processing parameters and width of laser beams.

Hybrid Laser Deposition of Fe-Based Metallic Powder under Cryogenic Conditions

“…This is because the laser beam offers many advantages, the most important of which are high flexibility, high power densities, localized or selective heating, high processing speed, and low heat input [9][10][11][12][13][14][15]. One of the areas of laser beam application that is currently being widely developed is shaping the properties of surface layers and manufacturing of coatings for enhanced wear characteristics (e.g., corrosion, tribological, abrasive, thermal, and mechanical fatigue or impact load) [16][17][18][19][20][21].…”

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

“…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]. One of the methods of improving properties is laser gas nitriding (LGN) of titanium and its alloys.…”

“…Laser gas nitriding involves heating or surface melting the titanium substrate in a nitrogen or nitrogen-rich atmosphere. 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, particularly in a liquid state.…”

“…% of nitrogen at 1050 °C). Due to this feature, a composite surface layer with in situ synthesized nitrides, embedded in the metallic matrix of titanium, can be formed during laser gas nitriding of titanium and titanium alloys [5,6,7,8,9,10,11]. Additionally, nitrogen has the effect of strengthening the structure, as an interstitial element, which distorts the lattice by occupying the available interstitial sites in the structure [7,11].…”

“…So far, the process of titanium nitriding has been carried out mainly by solid state Nd:YAG (Yttrium-Aluminum Garnet doped with neodymium ions) and gaseous CO 2 lasers that emit radiation with a wavelength of 1.06 and 10.6 µm, respectively [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. The next generation of lasers recently introduced to the industry are high power diode lasers.…”