| CAO Xin,WANG Jing-jing,LI Cong-jian,HE Wei-feng,WANG Lu-lu,HE Lei.Effect and Mechanism of Bias-graded TiAlN Coatings on Vibration and Tensile Fatigue Properties of TC4 Titanium Alloy[J],52(10):376-383 |
| Effect and Mechanism of Bias-graded TiAlN Coatings on Vibration and Tensile Fatigue Properties of TC4 Titanium Alloy |
| Received:September 07, 2022 Revised:February 13, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.10.033 |
| KeyWord:TiAlN coating bias-graded structure TC4 titanium alloy fatigue property damage mechanism |
| Author | Institution |
| CAO Xin |
High Speed Aerodynamics Institute, China Aerodynamics Research and Development Center, Sichuan Mianyang , China |
| WANG Jing-jing |
Institute of Biomedicine and Medical Devices, Southeast University, Jiangsu Taizhou , China |
| LI Cong-jian |
High Speed Aerodynamics Institute, China Aerodynamics Research and Development Center, Sichuan Mianyang , China |
| HE Wei-feng |
Science and Technology on Plasma Dynamics Laboratory, Air Force Engineering University, Xi'an , China |
| WANG Lu-lu |
High Speed Aerodynamics Institute, China Aerodynamics Research and Development Center, Sichuan Mianyang , China |
| HE Lei |
High Speed Aerodynamics Institute, China Aerodynamics Research and Development Center, Sichuan Mianyang , China |
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| Abstract: |
| The erosion resistant coating on the surface of the blade material can improve the sand protection performance. However, the aero-engine compressor blades are subject to the airflow excitation force aroused during the working process, causing the resonance of the blade in the low-order mode. The blades rotate at high speed, bearing huge centrifugal force. After the anti-erosion coating is prepared on the surface of the blade material, it is prone to cause fatigue damage together with the substrate under the above two types of alternating load, influencing the fatigue performance of the substrate. To investigate the effect of the coating on the fatigue properties of the substrate and the fatigue damage mechanism, bias-graded TiAlN coatings was deposited on Ti6Al4V alloy substrates using filtered cathodic vacuum arc (FCVA) technology with the bias-graded deposition method, during which the negative bias was changed gradually from ‒50 V to ‒200 V. The microstructure of the bias-graded TiAlN coating was observed and examined with a scanning electron microscopy. The basic mechanical properties including the element distribution along the depth direction, internal stress, surface hardness and film-substrate bonding force were characterized by an energy dispersive spectroscopy, a profilometer, a nanoindentation and scratch meter, respectively. The vibration and tensile fatigue properties of the bias-graded TiAlN coating/ substrate specimens were evaluated and the fatigue damage mechanism was analyzed by observing the fatigue fracture morphologies of the specimens. The results showed that the coating surface was dense and uniform with few droplets. The Al content along the depth direction of the TiAlN coating was decreased gradually, indicating the gradient structure coating was successfully prepared. The internal stress of the bias-graded TiAlN coating was (2.66±0.23) GPa, which was in a compressive state and significantly lower than that of the constant-bias coating. The inner defects created under the lower bias were more easily removed by the ad-atoms formed under the higher bias during the diffusion process, leading to the lower internal stress in the bias-graded TiAlN coating. The binding force of the bias-graded TiAlN coating was 44.03 N, which was much higher than that of the constant bias TiAlN (‒200 V) coating. The gradient structure could reduce the stress concentration and the internal stress of the coating, improve the crack resistance of the coating under vertical load, thereby increasing the bonding force between the coating and the substrate. The average vibration strength and tensile fatigue strength of the TiAlN coating specimens were 370.90 MPa and 377.90 MPa, respectively. The former was increased by 47.7% compared with the TC4 substrate, and the latter was almost unchanged. The residual compressive stress existed in the TiAlN coating can resistant to crack initiation. After the bias-graded TiAlN coating is prepared on the surface of the TC4 specimen, the fatigue crack sources under the two types of loading are both located at the interface between the coating and the substrate. For the vibration loading, the gradient structure in the coating inhibits the growth of cracks, and thus the fatigue strength increases. While for the tensile loading, the TiAlN coating is partially broken, and the two mechanisms of inhibiting crack initiation and promoting crack growth exist simultaneously, thus the fatigue strength is almost unchanged. |
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