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Femtosecond Pulsed Laser Deposition of Chromium Diboride-Rich Thin Films
摘要： Chromium borides are promising candidates for several structural applications including protective coatings for materials exposed to corrosive and abrasive environments. In this paper the pulsed laser deposition of chromium diboride-rich thin ?lms has been carried out in vacuum by using a frequency doubled Nd:glass laser with a pulse duration of 250 fs. The ?lms have been deposited at di?erent substrate temperatures and characterized by X-ray di?raction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Lastly, the ?lm’s hardness has been studied by Vickers indentation technique. The results indicate that only the ?lms deposited at a substrate temperature of 500 C are crystalline and formed by chromium diboride, together with a certain amount of boron and chromium, which suggests that, as main mechanism, a process taking place on the surface from atoms and ions from the gas phase. This hypothesis has been con?rmed by the study of the plasma produced by the ablation process.
关键词： thin ?lms,pulsed laser deposition,chromium diboride,ultra-short pulse laser
更新于2025-09-16 10:30:52
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Microstructural and Metallurgical Assessment of the Laser-Patterned Cemented Tungsten Carbide (WC-CoNi)
摘要： Cemented carbide is difficult to machine using traditional chip-removal methods due to its hardness. Electrical discharge machining (EDM) is the common method applied to shape cemented carbides because high geometric precision can be achieved. However, some important defects (pores, residual stresses or oxidation products) can be induced due to thermal reactions. Ultra-short pulse laser processing can also provide high precision and meanwhile effectively avoid these defects due to its short laser-matter reaction time. In this paper, three different patterns on WC-CoNi cemented carbides for tribological purposes, namely line-like patterns, dimples and grooves, have been created using different laser set-ups with pulse duration in the range of nanoseconds (10-9s), picoseconds (10-12s) and femtoseconds (10-15s). Microstructural and metallurgical changes of modified surfaces have been studied. Laser scanning microscopy (LSM) is conducted to measure the pattern dimensions. Focused ion beam (FIB) in combination with scanning electron microscope (SEM) is used to investigate the microstructural changes of the patterned materials.
关键词： Surface integrity,Laser surface patterning (LST),Cemented carbide,Ultra-short pulse laser processing
更新于2025-09-12 10:27:22
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An industry-relevant method to determine material-specific parameters for ultra-short pulsed laser ablation of cemented carbide
摘要： In recent years, it has been shown that ultra-short pulsed lasers can be used for the post processing and the fabrication of cutting tools. This new manufacturing technology can compete with the mainly used grinding process due to its ability to ablate materials independent of their hardness and without any wear. The knowledge of material properties is necessary for an optimal choice of machining parameters and the prediction of the ablation process. Measuring them is challenging, especially for inhomogeneous, ultra-hard materials. In this paper, an industry-relevant method is presented, which enables to determine the threshold fluence and the optical properties of cemented carbide. The required material-specific parameters are derived from simple ablation experiments, which are carried out on a modern laser machining center. Finally, the results are used to present a formula to calculate the material removal rate at different angles of incidence of the laser beam.
关键词： Neuenschwander model,ultra-short pulse laser machining,ablation efficiency,inclined incidence,threshold fluence,ablation rate,cemented carbide
更新于2025-09-12 10:27:22