Advanced Materials Research Vols. 941-944

Abstract: To establish a mathematical relationship between Nd:YAG laser parameters and the qualities of laser direct marked Data Matrix symbols on titanium alloys, multiple linear regression analyses were performed based on orthogonal experiment results. According to the analysis results, the paper developed a prediction model to estimate the contrasts of laser direct marked Data Matrix symbols (i.e. Symbol Contrast). The prediction model was statistically analyzed by regression analysis and multi-factor analysis of variance (ANOVA). The predicted symbol contrasts were compared with the experimental values and they were close. The multiple linear regression analyses results showed that the developed prediction model was extremely significant and could be used to estimate the symbol contrast in laser direct part marking.

Abstract: Laser direct-part marking is finding increasing use in the tracking of products as they pass through a manufacturing process. But too high heat input of the laser may cause deformation of the product beyond the limit of the drawing. In order to investigate the effect of laser marked Data Matrix symbol on titanium alloy, a Q-switched lamp pumped Nd:YAG laser was used in this research. Two Data Matrix symbols using 16A and 28A of electric current were marked respectively in the center of two titanium alloy sheets with 50mm length and 50mm width and 2mm thickness. To analyze the quality of the laser marking, environmental scanning electron microscope (ESEM) and X-ray diffractometer (XRD) were used. Experimental results showed the HAN’S Q-switched lamp pumped Nd:YAG laser marking system did not cause damage to the titanium alloy.

Abstract: A wavelength of 1064nm Nd: YAG laser was used to groove on silicon, then studying the affect of quality and processing efficiency by incoming jet in laser etching course of silicon: Water jet reduced doss, cracks and other defects which might be produced on the surface of groove. Software of matlab was used to restore the topography of tank’s bottom; analysis shown that the water jet had a scouring effect influence on tank’s bottom. Introduction of the water jet caused the loss of the laser energy, but it could improve processing efficiency indirectly by blowing away the slag.

Abstract: A water jet assisted laser composite processing device was used to study the influence of the laser input current and low-speed jet to etching amount .It established a empirical formula for relationship between the input current and the etching amount. Tests showed: under certain water speed, as the laser input current increased , the amount of etching was also increased; and when the current was constant, the jet speed was 25.9m/s, the etching amount reached a peak. This test also analyzed the factors that influenced the etching amount of water jets.

Abstract: Thin wall was formed by multi-layer overlapping laser cladding. The results showed that the surface of thin wall presents granular. Laser remelting could obviously improve the surface finish of the thin wall because of the melt of small granules. Match between the laser beam and the powder stream is very important and directly affects the forming quality. The microstructure of the thin wall presented obviously and continuously grown dendrite. Individual layers form metallurgic bonding and ensure whole properties of the cladding thin wall.

Abstract: Al₂O₃-TiC composite ceramic coatings were obtained by laser-assisted combustion. Al-TiO₂-C precursor powder mixture was coated on a medium-carbon steel substrate. When a laser scanned on the powder mixture, it went through combustion synthesis reaction triggered by the incident laser beam and formed the target products. The microstructure of the obtained coatings with different laser processing parameters was characterized using field emission scanning electron microscopy. The laser energy density, controlled by changing laser power and laser scanning speed, was found to play an important role on the microstructure of the products. The formation mechanism of different micro-morphologies with different laser energy densities was proposed according to thermodynamic calculation.

Abstract: Direct fabrication of end-use parts made of metal material has become one of the most interesting fields relevant to research and development of additive manufacturing technologies. This paper presents an effort of trial manufacture of a metal mouse mold with good performances of dimensional precision and fine surface roughness using direct manufacturing technology. The PDM (Plasma Deposition Manufacturing) process is adopted to couple with the milling process, which synthesizes plasma deposition as an additive technique, and milling as a subtractive technique during the processing. Plasma deposition manufacturing is demonstrated to allow rapidly fabricating the metal mouse mold directly from its CAD model without mold or tooling-based intermediary processes. The PDM method provides a new access to directly manufacture the metal parts and mold with short-process and high quality.

Abstract: Experiments on selective laser sintering of iron based alloy and nano-Al₂O₃ ceramic bulk materials are carried out and effect of sintering parameters on the process is analyzed systematically. A reasonable selective laser sintering technique which can be used to fabricate parts with free shape is obtained and verified with a multilayer sintering experiment. The component and the microstructure of the sintering production is tested. The influences of parameters and the amount of nano-Al₂O₃ on microstructure and microhardness of the sintering parts are studied. Laser sintering iron-based alloy experiments show that: microhardness has been noticeably improved. It is indicated that with the selective laser sintering technique obtained above, nano-alumina can be processed to manufacture three-dimension parts with free shape. With the addition of Al₂O₃ and the increase of composite parts of the grain gradually thinning, microhardness gradually improved nanocomposite parts for the microstructure of the dendrite skeleton-shaped crystal and the plane together, the internal Al₂O₃ dispersion organizations to strengthen the implicit crystal martensite and ferrite mixed organizations.

Abstract: 316 stainless steel was surface cladded with Co-based alloy using a high power semiconductor laser system. Microstructure, chemical composition, constituent phases and microhardness of the clad coating were investigated with SEM, EDS, XRD and Vickers hardness tester, respectively. The experimental results show that the microstructure of the layer is dense, no voids, cracks or other defects appearing and metallurgical bond between coating and substrate is perfect, The clad layer was mainly consisted of a fine dendritic structure, the constituent phases of the clad layer are mainly composed of γ-Co, (Cr,Mo)₂₃C₆ and Cr₇C₃, the microhardness of clad layer reaches about 720HV, which is about 3 times larger than that of the 316 stainless steel substrate.

Abstract: TiC_0.3N_0.7/TiN composite film was successfully formed on the surface of Ti-6Al-4V alloy by the treatment of YAG laser irradiation. In this paper an influence of laser output power on microstructure, chemical composition, element distribution and hardness, which were separately analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe micro-analyzer (EPMA) and nanoindentation hardness test, was investigated. Results showed that cross-section microstructure as-observed near the surface can be divided into three areas which were TiC_0.3N_0.7/TiN composite film, acicular structure and coarsening area, respectively. With increasing the output power, the thickness and the hardness of the TiC_0.3N_0.7/TiN layer were significantly improved.