Laser gas assisted treatment of pre-prepared high strength low alloy steel surface

A carbon film containing 5% volume fraction of TiC particles is formed using the phenolic resin on the workpiece surfaces prior to laser treatment process. The microstructural and morphological changes in the laser treated region are examined by optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction. The residual stress formed at the surface vicinity is obtained using the X-ray diffraction technique. Temperature and stress fields developed during laser treatment process are simulated incorporating the finite element code. Temperature predictions are validated with the thermocouple measurements. It is found that laser treated surfaces are free from defects such as voids, cavities, and cracks. The formation of dense layer with fine grains and nitride compounds as well as presence of TiC particles at the surface vicinity significantly increases hardness of laser treated surface. The residual stress predicted at the surface vicinity agrees well with that obtained from the X-ray diffraction technique.

► Dense layer with fine grains was formed at surface vicinity after laser treatment process.
► Nitride compounds formed and TiC particles increased hardness at treated surface.
► High stress field was developed in surface region due to large temperature gradients.
► The residual stress predicted agreed well with that of X-ray diffraction technique.