| LIU Wenrong,HU Yining,CHEN Siyu,WANG Tao.Microstructure and Corrosion Resistance of Titanium Alloy Reinforced with Nano-TiN[J],54(8):126-135 |
| Microstructure and Corrosion Resistance of Titanium Alloy Reinforced with Nano-TiN |
| Received:June 20, 2024 Revised:November 29, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.08.011 |
| KeyWord:laser directed energy deposition electrochemical corrosion nano-TiN TC4 alloy microstructure corrosion behavior |
| Author | Institution |
| LIU Wenrong |
College of Information Engineering, Qingdao Institute of Technology, Shandong Qingdao , China |
| HU Yining |
College of Aeronautical Engineering, Civil Aviation University of China, Tianjin , China |
| CHEN Siyu |
College of Aeronautical Engineering, Civil Aviation University of China, Tianjin , China |
| WANG Tao |
College of Aeronautical Engineering, Civil Aviation University of China, Tianjin , China |
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| Abstract: |
| As the operating environments for TC4 alloy become increasingly extreme, corrosion damage caused by conditions such as acidity, alkalinity, high temperature, and cyclic loading is becoming more severe. To enhance the corrosion resistance of TC4 titanium alloy, a nano-TiN ceramic particle reinforced TC4 composite was fabricated using laser directed energy deposition technology on a TC4 substrate. The process parameters are as follows:laser power of 2 100 W, scanning speed of 20 mm/s, powder feed rate of 23.326 g/min, spot diameter of 3.8 mm, and overlap rate of 55%. The powder ratio is 10 wt.% nano-TiN and 90wt.% TC4 powder. The TC4 and nano-TiN/TC4 samples were immersed in a 3.5wt.% NaCl solution for 1 hour for electrochemical experiments to analyze and evaluate their corrosion resistance. The phase structure, microstructure, corrosion morphology, and elemental distribution of the materials were analyzed with an X-ray diffractometer and a scanning electron microscope equipped with energy-dispersive spectroscopy, providing comprehensive insights into their properties and performance. The results indicate that after adding nano-TiN, the nano-TiN/TC4 composite exhibits multiple low-intensity TiN diffraction peaks. Due to the formation of interstitial solid solution of Ti and N atoms in the TC4 matrix, the interplanar spacing of the nano-TiN/TC4 composite increases, causing the diffraction peaks to shift to the left. From a macroscopic perspective, the TC4 and nano-TiN/TC4 coatings exhibit excellent metallurgical bonding with the substrate, without obvious cracks. Nano-TiN absorbs more laser energy, resulting in a higher dilution rate of the nano-TiN/TC4 coating and an increased deposition layer thickness. In the microstructure of nano-TiN/TC4, the complete melting of nano-TiN promoted the precipitation of blocky and strip-like TiXN phases within the nano-TiN/TC4 composite. The N content in blocky TiXN phases is higher than that in strip-like TiXN phases, indicating that as the N content decreases, the size of the precipitated TiXN phases decreases. The secondary precipitated TiXN dispersed distribution in the microstructure provides numerous nucleation sites, promoting the transformation of nano-TiN/TC4 grains into equiaxed crystals. When immersed for 1 hour, the corrosion current densities of the TC4 alloy and the nano TiN/TC4 composite are 35.665 nA/cm2 and 14.819 nA/cm2, respectively, with polarization resistance of 2 084 Ω and 2 696 Ω. After immersing for 10 days, the corrosion current density of TC4 increases, while that of the nano TiN/TC4 decreases to 4.458 nA/cm2, and the polarization resistance increases to 4 253 Ω. The passive film formed on the surfaces of the TC4 alloy and nano-TiN/TC4 composite is mainly composed of TiO2. The passivation film resistance of nano-TiN/TC4 is approximately 34.8 times that of TC4, indicating that nano-TiN/TC4 is more likely to form a high-quality passivation film. Due to TiXN acting as a micro-cathode, it preferentially induces the composite to enter a passivation state, making the corrosion resistance of the nano-TiN/TC4 composite significantly superior to that of TC4. On the surface of TC4, there are numerous point-like and strip-like pits, whereas in the nano-TiN/TC4 composite, the number and size of pits decrease, resulting in shallower corrosion traces. The addition of nano-TiN can effectively enhance the corrosion resistance of the TC4 alloy. |
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