Session: 02-01-02: 7th Annual Conference-Wide Symposium on Additive Manufacturing: Metals II

Paper Number: 95392

95392 - Effect of Heat Treatment on the Oxidation and High Temperature Wear Performance of Alloy Ti-6Al-4V Manufactured by Direct Metal Laser Sintering 

Ti-6Al-4V is a widely used alloy in aerospace, biomedical, marine and chemical industries due to it high strength, low density and excellent corrosion resistance. In this work, alloy Ti-6Al-4V was fabricated using direct metal laser sintering (DMLS) approach and studied the effect of heat treatment (solution treatment 950 ⁰C/2h-furnace cooling and aging 540 ⁰C/4h-air cooling) on the oxidation and wear performance at elevated temperature. The microstructural investigation revealed that as-built alloy consists of a fine-grained martensitic needle shape structure with columnar grains, which is transformed into a heterogeneous mixture of lamellar β and α after the heat treatment. In the solution treatment aging (STA) treated alloy, the rod-shaped β with different lengths of α was observed in different regions. No significant micro-segregation was noticed as well as some microspores were observed. The micro-hardness of the alloys was measured using a Vickers micro-hardness tester, and the results showed that the hardness of the alloy was significantly decreased by heat treatment due to the formation of coarsening microstructure. As-built and STA-treated alloy Ti-6Al-4V were subjected to cyclic oxidation test at 650 ⁰C for 50 h in air. The kinetic characteristics of the samples were established using the weight change method. The surface and phases of the reaction products developed on the surface of the samples are characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). A thick TiO₂ layer was formed on the alloy surface, and some cracks were noticed due to thermal stress. The cross-sectional investigation by SEM showed the developed scales on the surface, and energy dispersive spectroscopy (EDS) line mapping was used to distribution of elements. The detailed oxidation mechanism was clearly explained by the scale formation on the alloy and the oxidation behavior of the alloy was mainly dependent on the microstructure and testing conditions. The high-temperature wear test was performed on the Ti-6Al-4V alloy at room temperature (RT), 300⁰C and 600 ⁰C using a reciprocating pin-on-disc tribometer in dry condition. Results exhibited that STA alloy had a higher wear rate and coefficient of friction (COF) as compared to that of as-built alloy. The worn surface of the wear-tested samples at different temperature testing conditions are analyzed by SEM, XRD, and EDS. The abrasive wear mechanism was found at RT, whereas oxidation and the adhesive mechanism was noticed at 300⁰C and 600 ⁰C. The wear mechanism divulged that the wear behavior of all the alloy samples were strongly related to the microstructure, microhardness and temperature. Based on the results, the STA treated alloy exhibits better oxidation and lower wear resistance as compared to the as-built alloy at elevated temperatures.   

Keywords: Ti-6Al-4V; Direct metal laser sintering; High temperature wear; Oxidation; Oxide scale; Mechanism

Presenting Author: Dhinakaran Veeman Chennai Institute of Technology

Presenting Author Biography: Dr V Dhinakaran is an experienced Professor with a demonstrated history of working in the higher education , Head at Centre for Additive Manufacturing in the Chennai Institute of Technology, Chennai, India. Currently he is working as Dean (Research &amp; Development). He expertise his skills in engineering, Finite Element Analysis (FEA), and Computational Fluid Dynamics, Composites, Welding, Additive Manufacturing and various other fields. Dr. V. Dhinakaran has given more than 35 expect lecture in various Engineering colleges in order to enhance the knowledge of Faculty members, Researchers and Student community. <br/><br/>Dr. V. Dhinakaran has published 48 SCIE articles and 84 Scopus indexed articles in peer-reviewed journals as well as he is the author and editor of various handbooks in research areas published with Elsevier, Taylor Francis, and Springer. He is an Associate Editor in Journal of robotics and control and Editorial Board member in American Research Journal of Biomedical Engineering, Youth Editorial Board Member of Advanced Powder Materials (APM).

Authors:

Ragavanantham Shanmugam NAVAJO TECHNICAL UNIVERSITY
Dhinakaran Veeman Chennai Institute of Technology
Muthu Shanmugam Mannan Chennai Institute of Technology
Gopika Kalaiselvan Chennai Institute of Technology