Papers by Author: M. Aslam

Abstract: Laser Induced Plasma Assisted Ablation (LIPAA) has been used to carry out back side dry etching/ablation of different optical glasses under vacuum. It is observed that etching depth increases with decrease in target-substrate gap and becomes maximum (50 μm) at zero gap size for steel-quartz pair. The maximum ablation depth for brass-quartz pair was 25 μm. The effects of laser power on etching depth and laser scan speed has also been reported.

Abstract: A 40W Nd:YAG laser has been used to carry out parametric study the etching depth (ablation depth) for different optical glasses using stainless steel, brass and silver as target materials by Laser Induced Plasma Assisted Ablation (LIPAA) process. A maximum ablation depth of 38m for fused quartz has been achieved with stainless steel as target material with a high ablation rate of 565nm/pulse. A surface roughness of 120nm has been measured for fused quartz with stainless steel as target.

Abstract: Laser surface hardening of plain carbon steel is simulated and software in Mathematica has been developed. The software estimates the hardness of plain carbon steel under different carbon contents and processing speeds. The flow chart explains the algorithm of the software. Our results show that hardness increases with carbon contents. The hardness increases slightly with processing speed but at the cost of decrease in hardened depth. The results for test material coincide with the experimental values from independent research results.

Abstract: Laser surface alloying of Ni-Co electroplated steel using 900 W CW CO2 laser to develop Fe-Ni-Co alloy on the surface is reported. Fe-Ni-Co alloys of different compositions are produced by varying the working speed from 0.25 m/min to 3m/min and laser spot size from 0.6 mm to 5mm. The development of microstructure in the melted zone is analysed in terms of composition variation and cooling rate. The microhardness of newly formed alloys reported here are three times higher as compared to base metal. Martensite is observed in the laser modified zone.

Abstract: Surface hardening of GCr15 bearing steel ring was carried out using CW CO2 laser. The laser power used was in the range of 300 to 500 Watts. A rectangular beam shape was used to cover the area to be hardened. A three fold increase in the hardness of the transformed zone was achieved. The depth of hardness attained was around 1mm. The depth and width of the laser treated zone were studied as function of laser power and working speed for specific spot size. The microstructure of the transformed zone is also discussed. Subzero cooling technique was applied to convert the retained austenite to martensite.

Abstract: Cutting of austenitic stainless steel of 0.5mm and 2mm thickness with CO2 laser has been carried out using oxygen, nitrogen and compressed air as assist gases. It has been observed that when oxygen is used as assist gas, the contribution of combustion energy was found to be 60 to 80 % more as compared to the other two types of assist gases. The cutting speed for 0.5 mm sheet was about 11 times where as for 2 mm stainless steel it was around 16 times. The role of combustion energy were theoretically calculated and compared with experimental results and found to be in good agreement.