Advanced Materials Research Vols. 291-294

Abstract: The scrap WC_P/Fe-C composites were re-melted in a 50 kg medium frequency induction furnace. A regenerated composites ring was manufactured by centrifugal casting process. The microstructure and properties of the composites before and after re-melting were investigated by SEM with energy dispersive spectroscopy and X-ray diffraction. The results showed that the microstructure of the composites after re-melting was composed of un-dissolved WC_P, bainite, bone-like crystallites and graphite. The un-dissolved WC_P were uniformly distributed in the outer region of the regenerated composites ring, their volume fraction attained to about 65 vol. %, and size of the un-dissolved WC_P was obviously smaller than that of the WC_P before re-melting. The impact toughness of the regenerated composites was below those of the composites before re-melting, the hardness and wear resistance of the regenerated composites were almost same as those of the composites before re-melting under the same test conditions.

Abstract: ITO electrode patterns were fabricated using excimer laser direct-writing technique. The influence of the process parameters (the excimer laser fluence and the stage velocity) on the micromachining quality (the etching depth and ridge height of the edge ) of ITO patterns were experimentally studied. In this paper, the effect of laser fluence and the speed of working platform on the fabrication quality were discussed. The lower laser fluence and suitable platform speed will be very helpful to improve the edge quality of patterning of ITO. However, the recast ridge at the edge also was shown. Use of 39% solution of hydrochloric acid made it possible to further minimize the recast ridge at the edges.

Abstract: In this paper the research focused on the viability of using the selective laser sintering (SLS) technique for creating tissue engineer (TE) scaffolds. A biocomposite blend comprising polylactic acid (PLA) and hydroxyapatite (HA) was used in the research to study the feasibility of the blend to develop scaffolds. The biocomposite blends obtained via physical blending were subjected to laser sintering to fabricate test specimens. The test specimens were characterized using scanning electron microscopy (SEM) and the components before sintering and after sintering were analyzed by infrared spectrophotometry (IR). The results obtained ascertained that SLS-fabricated scaffolds have good potential for TE applications

Abstract: The past studies indicated that thermal fatigue resistance of cast irons could be improved by partly laser melting treatment. However the only disadvantage of this technology is that the enhancement of thermal fatigue resistance would be limited because of the fixed chemical composition of sample matrix. For this purpose, the laser surface alloying of CrNi was selected for changing both the compositions and the microstructures of laser treated zone, and the effects of alloy powder compositions on thermal fatigue behavior were also investigated in this paper. The results indicate that the alloy elements distribute homogeneously, and their contents increase markedly in the non-smooth unit on the alloyed layer. The non-smooth unit is strengthened further compared with laser melting treatment. Thermal fatigue resistance of cast iron is enhanced evidently by laser surface alloying of CrNi powders, and for all samples tested, those treated with 25%Cr-75%Ni powders have the best thermal fatigue resistance.

Abstract: Laser surface texturing improved tribological property is regarded as an optimistic method. However, many technological parameters have crisscross effects on surface topographies, the complexity of relations between variables devoted to a tough way to express functions accurately. Meanwhile, enough basic tents of theory can be borrowed to interruption for obtained the expectation in the process of micro-texturing on critical surfaces. And thus pumping current and number of laser pulse were chosen and studied for improving the surface topographies realized by Nd³⁺: YAG laser, assisting a better expectation of reduction of abrasive grains. The single-factor method was exerted in the process of analysis, one international 3D-morphology meter and its accessory codes were adopted before the analysis of constitutive influence from pumping current and pulse times in given duration on characteristic parameters of texturing surface, the results are shown in figures by Abbott curve and characteristic parameters which were compared in the literate.

Abstract: Laser cladding has been taken into consideration for repairing K418 Ni-based superalloy material with CoCrNiW powder.Composition of cladding materials was revealed by energy dispersive X-ray spectrum(EDS). The characteristic microstructure of the cladding layer and interface were investigated by using an optical microscope and scanning electron microscope(SEM).Cladding coatings were obtained for different process parameters, and a detailed study of the effects of these parameters has been carried out by SEM. Metallurgical bonding between the cladding layer and substrate materials was obtained.Effect of heat input on cladding cracking susceptibility has been studied to obtain optimum condition for crack-free welds. Variations in cracking susceptibility as a function of heat input is discussed with reference to metallurgical characteristics of the clads. The corresponding microstructure induced by different heat input was discussed in this paper too.

Abstract: 30CrMnSi is quenched and tempered steel with medium hardenability, and good mechanical properties. However, the anti-corrosion of the weld heat affected zone will be decreased, which will lead to the worse overall properties of parts. The anti-corrosion properties of heat affected zone will be improved by YAG laser treatment according optimized processing parameters. The microstructure of the modified heat affected zone was observed and analyzed in this paper. And the anti-corrosion property was studied also. The results showed that the anti-corrosion property of heat affected zone will be improved by laser remelting technology. The laser anti-corrosion is the effective method to enhance anti-corrosion property.

Abstract: Laser surface remelting and alloying of sintered stainless steel type 410L with FeNi and Ni have been studied for improvement of corrosion resistance and hardness increase. The influences of high power diode laser (HPDL) processing conditions, laser power in range 0.7-2.1 kW on the microstructure and properties of alloyed surface layer have been evaluated. The FeNi alloyed layer shows microstructure composed of austenite and martensite formed, due to high cooling rate in laser remelting process, with average Ni content in range of 39 to 8% depending on laser processing conditions. The Ni alloyed layer was composed of austenitic microstructure with Ni content from 65% to 33%. The improvement in microhardness was achieved by laser surface alloying and remelting. Excellent corrosion properties were observed for such remelted and alloyed layers in salt spray test.

Abstract: Laser surface cladding was carried out on a Mg-Al-Zn system ZM5 magnesium alloy with a mixture of Al and nano-Al₂O₃ powders. The microstructure, chemical composition analyses of the cladding coating were studied by scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDAX).Both the coating and substrate were identied by microhardness tester. The laser cladding showed very good bonding with the magnesium alloy substrate. The Al₂O₃ particles partially or completely melted during laser irradiation and re-solidified with irregular shapes in the size range of 5–60 µm along with a few islands as large as 500 µm, within the grain-refined Mg-rich dendritic matrix. The improvement in microhardness after cladding was attributed to the presence of ultra-hard Al₂O₃ particles, increased solid solubility of Al and a very fine dendritic microstructure as a result of rapid solidification induced by laser cladding process. And corrosion resistance of the cladded coating was enhanced compared to that of the as-cast substrate after immersion tests.

Abstract: In order to determine the optimum joint conditions, four key process parameters affecting the joint quality of laser transmission joint of 1mm thick PET film and PC film，namely，laser power, scanning speed, clamping pressure and scanning number are optimized by response surface methodology in this paper. The interaction effect of main process parameters on joint quality is researched. The samples are tested using a multi-axis microtester in order to determine joint strength. The morphology of the joining area is observed with an optical microscope. Design Expert analysis indicates that the best laser power, scanning speed, clamping pressure and scanning number on joint quality were 35.7W, 5.0mm/s, 0.75MPa, 3, respectively. Finally, the experimental results are consistent with the predicted, which illustrates that the developed mathematical models can predict the responses adequately.