Laser Surface Modification of TC21 (α/β) Titanium Alloy Using a Direct Energy Deposition (DED) Process

Abstract

The TC21 alloy (Ti-6Al-3Mo-1.9Nb-2.2Sn-2.2Zr-1.5Cr) is considered a new titanium alloy that replaced the commercial Ti-6Al-4V alloy in aerospace applications due to its higher operating temperatures. Recently, direct energy deposition was usually applied to enhance the hardness, tribological properties, and corrosion resistance for many alloys. Consequently, this study was performed by utilizing direct energy deposition (DED) on TC21 (α/β) titanium alloy to improve their mechanical properties by depositing a mixture powder of stellite-6 (Co-based alloy) and tungsten carbides particles (WC). Different WC percentages were applied to the surfaces of TC21 using a 4 kW continuous-wave fiber-coupled diode laser at a constant powder feeding rate. This study aimed to obtain a uniform distribution of hard surfaces containing undissolved WC particles that were dispersed in a Co-based alloy matrix to enhance the wear resistance of such alloys. Scanning electron microscopy, energy dispersive X-ray analysis (EDAX), and X-ray diffractometry (XRD) were used to characterize the deposited layers. New constituents and intermetallic compounds were found in the deposited layers. The microhardness was measured for all deposited layers and wear resistance was evaluated at room temperature using a dry sliding ball during a disk abrasion test. The results showed that the microstructure of the deposited layer consisted of a hypereutectic structure and undissolved tungsten carbide dispersed in the matrix of the Co-based alloy that depended on the WC weight fraction. The microhardness values increased with increasing WC weight fraction in the deposited powder by more than threefold as compared with the as-cast samples. A notable enhancement of wear resistance of the deposited layers was thus achieved.

Impact of laser process parameters in direct energy deposition on microstructure, layer characteristics, and microhardness of TC21 alloy

“…To investigate the influence of DED process parameters on quality characteristics and microhardness of deposited layer, a series of powder feeding rates were attempted as listed in Table 1. According to our previous work [19], the best mixture composition of deposited powder was 60% WC + 40% Stellite-6. Therefore, the same powder composition was used with different powder feeding rates.…”

“…The data of DED with the preblended powder of Stellite-6 plus WC on TC21 alloy and its effect on microstructure, microhardness, as well as wear resistance have already been published for the first time in our previous work [19]. Three different WC fractions in the Co-based alloy powder were applied to the surfaces of TC21 alloy using a 4 kW continuous-wave fiber-coupled diode laser at a constant powder feeding rate to improve their mechanical properties.…”

Studies of Highly Dispersed Titanium Carbide Powder Obtained from Scrap Tungstenless Cemented Carbide Alloys

“…Titanium carbide is one of the most demanded materials widely used in industry, modern engineering and medicine [1][2][3]. The wide range of applications is due to the unique combination of chemical and physical properties of titanium carbide (high wear resistance, corrosion resistance, chemical inertness, high melting point, flexural modulus, etc.)…”

Effect of oxide layers formed by thermal oxidation on mechanical properties and NaCl-induced hot corrosion behavior of TC21 Ti-alloy

“…However, due to low high-temperature oxidation resistance, its use in high-temperature aviation components is still restricted. Various coating methods, such as electron-beam physical vapor deposition 23 , laser cladding 24,25 , plasma spraying 26 , sol-gel 27 , arc ion plating 28 , hot dipping 29 , plasma electrolytic oxidation (PEO) 30 , and magnetron sputtering 31 have been studied to enhance of high temperature oxidation resistance. The most recent research on the TC21 alloy focuses on its mechanical characteristics and microstructure change following heat treatment 21,32 .…”