| REN Zhiguo,WANG Shuo,WANG Zhenxing,HAO Jun,LIANG Jianming.Effect of Laser Derusting Technology on Surface Residual Stress and Corrosion Properties of Q345 Steel[J],53(19):164-172 |
| Effect of Laser Derusting Technology on Surface Residual Stress and Corrosion Properties of Q345 Steel |
| Received:October 23, 2023 Revised:April 28, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.19.015 |
| KeyWord:laser derusting Q345 steel residual stress corrosion performance surface treatment |
| Author | Institution |
| REN Zhiguo |
School of Mechanical Engineering, Hebei University of Architecture, Hebei Zhangjiakou , China;Central Iron and Steel Research Institute, Beijing , China |
| WANG Shuo |
School of Mechanical Engineering, Hebei University of Architecture, Hebei Zhangjiakou , China |
| WANG Zhenxing |
School of Mechanical Engineering, Hebei University of Architecture, Hebei Zhangjiakou , China |
| HAO Jun |
Zhonglong Electromechanical Zhuolu Company, Hebei Zhangjiakou , China |
| LIANG Jianming |
School of Mechanical Engineering, Hebei University of Architecture, Hebei Zhangjiakou , China |
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| Abstract: |
| Laser derusting technology is an advanced surface treatment technology and due to its high cleaning degree, good control, green environmental protection and other advantages, it is widely used, especially in the rust and paint removal industry. However, in the process of laser derusting, in addition to the interaction between laser and surface contaminants, laser will also interact with the sample substrate, which will affect the microstructure, crystal structure and surface properties of the near surface of the sample substrate. Only by exploring the effect law of laser on the near surface of the sample, the laser cleaning technology can be better applied to the engineering field. In the process of laser derusting, residual stress is likely to occur near the surface of metal substrate due to local laser heat treatment. The existence of residual stress near the surface not only affects the surface mechanical properties, but more importantly, it may accelerate the corrosion rate of the metal substrate, reduce the corrosion resistance of the metal substrate, and affect the service life of the component. Therefore, in the process of laser derusting, whether the near surface of the metal substrate will produce residual stress, what type of residual stress will be generated, and what kind of change occurs in the corrosion resistance of the metal substrate surface are all crucial. The corrosion on the surface of Q345 steel is mainly composed of a mixture of Fe oxides and their hydrates, so the content of oxygen elements on the surface of the sample can effectively characterize the effect of laser derusting. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the surface morphology and oxygen content of laser derusting samples. The results of EDS showed that there was no oxygen content on the surface of metal substrate after laser derusting. According to the cleaning effect and surface topography, the optimal parameters of laser derusting were determined as laser power 16 W, laser repetition rate 70 kHz and laser scanning speed 1.0 m/s. Metallographic microscope was used to observe the cross section of the metal substrate after laser derusting. According to the different microstructure characteristics of the cross section, it was divided into the base material (BM) and the heat affected layer (HAL). The depth of the heat affected layer was about 25 μm. According to the contrast of the metallographic microstructure, the microstructure of the heat-affected layer was composed of ferrite and microstructure A, and the ferrite content of the heat-affected layer was reduced. Back scattered electron diffractometer (EBSD) was used to scan the surface of the original sample and the sample after laser derusting, and the residual stress on the metal substrate surface was qualitatively characterized by the orientation difference imaging method. Back scattered electron diffractometer (EBSD) can only qualitatively characterize whether laser derusting technology can produce residual stress on the metal substrate surface. If the type and magnitude of residual stress are to be further measured, it is still necessary to select a suitable test method. Considering that the effect depth of laser derusting on metal substrate is only 25 mm, the residual stress on metal substrate surface is measured by X-ray diffraction method. In the process of laser derusting, due to the localized heating of the laser spot and the metal material within the effective heating range of the laser spot melts, with the movement of the laser spot, the metal material in the melting zone solidifies and cools, and is constrained and hindered by the surrounding cooler metal, resulting in a residual tensile stress of about 100-150 MPa. Potentiodynamic polarization curve and zero resistance amperometry (ZRA) are used to characterize the surface corrosion resistance of the original sample and the sample after laser derusting. The results show that in the process of laser derusting, the content of cementite and ferrite in the heat-affected layer decreases, the ratio of cementite to ferrite increases, the self-corrosion potential increases to −490 mV, and the corrosion current density decreases to 17 μA/cm2, and the corrosion resistance of the sample surface improves. Therefore, in the process of laser derusting, due to the effect of laser and metal substrate, although residual tensile stress is generated on the surface of the metal substrate, a heat-affected layer with a thickness of about 25 mm is formed near the surface. Under the combined action, the corrosion resistance of the sample surface after laser derusting is improved and the service life is prolonged. |
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