Author: Tse, Ki-kwai Godwin
Title: Application of laser processing for tools of the semiconductor industry
Degree: M.Sc.
Year: 1999
Subject: Semiconductor industry -- Laser use in
Lasers -- Industrial applications
Laser welding
Manufacturing processes
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Department of Manufacturing Engineering
Pages: 166, [25] leaves : ill. (chiefly col.) ; 31 cm
Language: English
Abstract: This project is a feasibility study on the characteristics of the fusion of tungsten carbide with mild steel materials (AISI 1015) by laser welding, and the welded joint was also investigated. Furthermore, laser surface alloying of Chromium Carbide material on mild steel using a high power continuous wave CO2 laser was also investigated. The effects of laser power and traverse speed were studied. The laser treated specimen were investigated using optical and scanning electron microscopy for the study of microstructure, topography, cracking and pores formation, and EDAX was used for compositional analysis on the alloyed region. For laser welding, plates of tungsten carbide and mild steel were successfully welded to each other using a continuous CO2 laser with argon as shielding gas. The position of the laser beam with respect to the joint interface and the power of the laser beam with respect to the traveling speed used were determined to be important factors that affect the weld quality. The best conditions for crack free welds in the 2 mm thick specimen were in the range of traverse speed 1500-3000 mm/min, and laser power 1.6-2 KW. The welds made with compressed air as the shielding gas exhibited excessive porosity, and the microstructural evaluation of the weld was carried out with the help of an EDAX analyzer. It revealed considerable inter-diffusion of tungsten carbide into the mild steel fusion zone and the components of the mild steel into the carbide zone. For laser surface alloying, case carburised mild steel specimen was chrome plated and the surface was subjected to laser surface melting. Microstructural study showed a high degree of grain refinement and an increase in hardness due to solid solubility of carbides element. This process produced a fine distribution of complex type of carbide precipitate in the martensite-ferrite-matrix because of the high cooling rate. Not much chromium was found to be alloyed in the surface.
Rights: All rights reserved
Access: restricted access

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