Y.P. Kathuria

Laser cladding of Stellite #6: a detailed analysis

Potential applications such as hard facing of engine valve seat, turbine engine blade shroud interlock and leading edge of steam turbine blade, with controlled dilution have stimulated the use of laser cladding recently. In this paper, based on the laser beam interaction time, the microscopical study of dendrite structure formation in laser cladding of stellite number 6 on mild steel and Cr-Ni base materials is investigated. The effect of the various parameters such as heat input, beam interaction time, scanning frequency and transverse speed are considered. The applications in the rapid prototyping industries are also discussed.

Blue spectral shift of P3HT organic film by KrF excimer laser ablation

A technique for morphology control of self-assembled organic films based on laser ablation is presented. The regioregular poly 3-hexylthiophene (RR-P3HT) films prepared by using drop casting method and spin coating method are irradiated and ablated by the ultraviolet KrF excimer laser. Absorption spectra and XRD profiles of the films are investigated. For spin coated films, Blue absorption spectral shift is observed; For drop cast films, Blue shift in the absorption spectra, accompanied with the disappearance of the peak intensity of XRD profiles, are observed. The results indicate that molecular structure has been changed due to photo-thermal effect and molecule cutting effect of laser ablation.

Precise micromaterial processing by excimer laser ablation

An ablation wave from materials based on laser supported detonation and laser supported combustion has been created by exposing them with laser. The purpose of this study is to analyse the mechanism of the ablation wave using a high speed streaked camera and to realize more precise microprocessing by controlling the wave. The laser used in this experiment was an ultraviolet XeCl excimer laser of high photon energy with a wavelength of 308nm, a maximum pulse energy of 500mJ, a pulse width of 30ns and a maximum frequency of 50Hz. The high speed streaked camera had a resolving power of 100ps. Metal-ceramics functionally graded materials (FGMs) were selected as sample materials. An experimental system of laser microprocessing was constructed and the behavior of the ablation wave from FGMs were observed. The experimental results showed that the mechanism of the ablation wave from FGMs was a photochemical reaction with thermal interaction.

Behavior of ablation wave from functionally graded materials by excimer laser

Abstract An ablation wave based on a laser induced detonation and laser supported combustion can been created by exposing various types of material to an excimer laser. The purpose of this study is to analyse the mechanism of the ablation wave using a high speed streak camera and to achieve greater precision in microprocessing and surface treatment by controlling the wave appropriately for each material. The laser used in this experiment was an ultraviolet pulse excimer laser with a wavelength of 308nm. For measurement, a video digital processing system with a high speed streak camera was used. Metal-ceramic functionally graded materials (FGMs) were selected as test materials. The experimental results showed that the mechanism of the ablation wave obtained from these FGMs was a photochemical reaction with thermal interaction.

Duty cycle and modulation effects in aluminum alloy welding with high-power Nd:YAG laser

The modulation and duty cycle effects on Al-alloy welding with high power Nd-YAG laser are investigated. Micro- structural characterization of the low and high duty welds with wave modulation identified the differences in the weld morphology. Welding depth, undercut and strength of fusion zone are discussed as a function of the processing parameters.