研究目的
The aim of this study is to improve the surface integrity of gray cast iron subjected to LCP. The process of bubble evolution, velocity field of bubble, impact of water-jet, deformation and stress were simulated. In the case of no coverage layer and 0.1 mm copper coverage layer, the surface morphology and roughness, micro-hardness and residual stress of HT200 cast iron subjected to LCP were investigated. The effects of laser energy and defocusing amount on the LCP were also investigated.
研究成果
The presence of copper coverage layer makes the plastic deformation more uniform and the HT200 surface more flat after the treatment of LCP, and the surface roughness decreases by half compared with that without coverage layer. In the case of no coverage layer, the improvement of micro-hardness and residual stress of HT200 after LCP - 200 mJ is the most significant, and the surface roughness is the lowest. Higher laser energy produces higher magnitude of micro-hardness and compressive residual stress in the case of coverage layer. The optimal parameter of defocusing amount for the compressive residual stress and micro-hardness is 1 mm at the case of no coverage layer while it is 0 mm at the case of coverage layer.
研究不足
The study focuses on the effects of a copper coverage layer on the surface integrity of HT200 gray cast iron subjected to LCP under various laser energies and defocusing amounts. The research does not explore the effects of other types of coverage layers or materials beyond HT200 gray cast iron. Additionally, the study is limited to the simulation and experimental investigation of the LCP process, without extending to long-term performance or industrial application scenarios.
1：Experimental Design and Method Selection
A Q-switched Nd: YAG laser with wavelength 1064 nm and 8 ns pulse width was employed to induce cavitation bubbles. The expanding lens system was employed to adjust the laser beam on the propagation path for avoiding the strip optical breakdown and the dispersion of laser energy. The depth of liquid was kept to nearly 10 mm from the specimen surface.
2：Sample Selection and Data Sources
The specimen adopted for the experiment was HT200 gray cast iron, and the dimension of specimen was 20 mm × 20 mm × 10 mm (width × length × thickness). The top surfaces of all specimens were polished using different grades of silicon carbide (SiC) papers with 200 - 2000 grit, followed by cleaning in an ultrasonic cleaner for 15 minutes and dried by a blower. Copper foil with a thickness of 0.1 mm was used as the coverage layer, which is directly bonded to the top surface of specimen.
3：List of Experimental Equipment and Materials
The experimental system consists of a nanosecond laser (Nd:YAG dual-wavelength solid-state laser, Kinder Optoelectronics Technology Co., Ltd.), three-dimensional mobile platform (SIMUMEIK-840Di, SIMENS), reflector lens, concave lens, convex lens and laser energy meter (NIM-E1000, China Institute of Metrology).
4：Experimental Procedures and Operational Workflow
The defocusing amount was adjusted through the three-dimensional mobile platform, and the pulse frequency was set to 1 Hz. The corresponding laser energy is from 100 mJ to 400 mJ, and with different defocusing amount varying from 0 to 2 mm, respectively. The scanning path of LCP was set with a 50% overlap ratio “Z”-shaped road map and the spot diameter employed was 0.5 mm.
5：Data Analysis Methods
The surface morphology and roughness of all cast iron specimens were measured by an ultra-high resolution true color confocal micro-scope (Axio CSM 700). The residual stress was measured by an X-350A residual stress tester with X-ray diffraction. The micro-hardness of all specimens were measured by a HV-1000 Vickers tester.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
