Experimental study and numerical simulation for the interaction between laser and PEEK with different crystallinity

Polyetheretherketone (PEEK) sheets with the thickness of 0.5 mm were prepared by compression molding process using Victrex PEEK-450PF, and then PEEK sheets with different crystallinities were obtained by controlling the cooling rate. The optical characteristics of the samples were respectively measured by laser power meter, UV-VIS-IR spectrophotometer. And with the process parameters of laser power density of 245 W/cm2 and moving speed of 5 mm/s, the effect of crystallinity on the laser energy absorption of PEEK and the influence of laser irradiation on the crystallization properties of PEEK sheets were systematically studied. Finally, numerical model of laser energy absorption by PEEK was constructed with COMSOL software. The results show that the reflectivity of PEEK will increase with the increase of crystallinity, while the transmittance decreases. The pure PEEK sheets do not strongly absorb the laser at the wavelength of 1070 nm and the amorphous PEEK is more likely to be ablated. Carbonized samples during the laser irradiation was taken for XRD test and found to be amorphous. After laser irradiation, the crystallinity of the semi-crystalline PEEK material will decrease, but the originally amorphous peek crystallinity will increase slightly. Besides, the numerical simulation results are in good agreement with the experimental results.

Effect of Graphene Oxide on the Performance of Co-Based Coatings on Ti6Al4V Alloys by Laser Cladding

In order to improve the hardness and wear resistance of Ti6Al4V alloys, Co-based coatings with different contents of graphene oxide (GO) were prepared on Ti6Al4V alloys by laser cladding. The effects of the graphene oxide content on the microstructure, hardness, and wear resistance were analyzed. It was found that carbides and undissolved graphene oxide films existed in the coating. Carbides contribute to grain refinement and improve the hardness of the coating. Graphene oxide films can improve the wear resistance of the coating. However, an excessive addition of graphene oxide affects the laser energy absorption of the coating. The results show that when the graphene oxide content is 0.5 wt.%, the performance of the coating is the best. Compared with the Co-based coating without graphene oxide addition, the hardness increased by 32.3%, the friction coefficient decreased by 27.2%, and the wear rate decreased by 66.5%.