Effect of Y 2 O 3 Addition on Microstructural Characteristics and Microhardness of Laser-Cladded Ti-6Al-4V Alloy Coating
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JMEPEG (2020) 29:8221–8235 https://doi.org/10.1007/s11665-020-05316-5
Effect of Y2O3 Addition on Microstructural Characteristics and Microhardness of Laser-Cladded Ti-6Al-4V Alloy Coating Tiangang Zhang, Haiqiang Xiao, Zhiqiang Zhang, Bo Yao, and Fan Yang Submitted: 20 March 2020 / Revised: 27 September 2020 / Accepted: 31 October 2020 / Published online: 18 November 2020 In this study, the effect of Y2O3 addition on the quality, microstructure, and microhardness of multi-track laser-cladded Ti-6Al-4V coating using coaxial powder feeding was investigated. These parameters were characterised via dye penetration, x-ray diffractometry, scanning electron microscopy, energy dispersive spectrometry, electron probe microanalysis, microhardness measurements, and ball-on-disc tribometer. It is observed that Y2O3 addition improved the coating quality by completely eliminating the formation of pores in multi-tracked Ti-6Al-4V coatings. The microstructure of the coating without and with Y2O3 primarily consists of acicular martensite (a¢-Ti). Furthermore, the continuity of original b-Ti grain boundary is broken by the introduction of Y2O3. In addition, the Y2O3 is adsorbed and pinned at the original b-Ti grain boundaries resulting in the refinement of the b-Ti grains. It is believed that the refinement in the original b-Ti grains occurs via inhibition of the movement of the grain solid–liquid interface through dragging action. This phenomenon hinders grain growth by acting as a heterogeneous nucleus rather than increasing nucleation rate because it exhibits high lattice misfit degree. Compared with the coating without the Y2O3, the microhardness and wear stability of the Y2O3-supplemented coating was improved because of grain boundary strengthening, fine-grained strengthening, addition of high hardness Y2O3, and elimination of pores. Keywords
forming quality, laser cladding, microhardness, microstructure, Ti-6Al-4V, Y2O3
1. Introduction Ti-6Al-4V titanium alloy has high specific strength, good thermal stability, and excellent resistance to oxidation and corrosion (Ref 1, 2); thus, it meets the material requirements of several aero engine key components that operate at low– medium temperatures, such as low-pressure compressor blades, fan blades, and crankcasts (Ref 1, 3, 4). However, these titanium alloy parts inevitably suffer from scratches and frictional wear caused by ingestion of foreign hard particles into aero engines because of their low hardness and poor abrasion resistance (Ref 5, 6). Laser cladding is a rapid and efficient surface engineering approach that has been widely used for damage repair, surface modification, and structural remanufacturing of titanium alloy parts owing to its advantages of considerably small structural distortion and low residual stress, convenience of automation, and excellent bonding strength between cladding layers and substrates (Ref 3, 7, 8). In practice, during the repair process,
Tiangang Zhang, Engineering Techniques Training Center, Civil Aviation University of China, Tianjin 3003
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