The Prevention of Crack Propagation in Metal Alloy by Laser Remelting

Abstract

There were many methods previously used to repair the cracks, induced during fatigue loading. The most commonly used was hole drilling method and then insertion of pins to increase the fatigue performance. Another method involving laser shockwave peening had been used to treat the surface cracks. The method similar to laser shockwave peening was studied in the present research, which comprises of laser remelting. The method was analyzed as a crack preventing technique. The laser re-melting scans were performed on a steel plate by varying the energy density and defocusing of the laser.. The samples were sectioned perpendicular to the laser scan and the cut surface was polished to a mirror finish using metallographic techniques including mounting, grinding and polishing. The microstructure was revealed by etching the polished surface that clearly exposed the grains structure in the optical microscope. The focus point of the laser beam was identified by the microstructural study of the samples. Hardness testing was performed to analyze the trend of the hardness throughout the sample including the base metal, HAZ and meltzone. Moreover, toughness was ascertained through the microstructural analysis that showed as grain size variations and phase changes. The microstructure toughness was considered to be the most crucial factor in analyzing the prevention strategies of fatigue crack propagation.