Flame-assisted laser surface treatment of refractory materials for crack-free densification

A study to improve the integrity and reliability of alumina-based refractory bricks, installed as linings in furnaces and incinerators, is being conducted. Owing to the inherent porosity of such heat-insulating materials, problems associated with molten slag penetration and chemical degradation are often encountered. It is known that denser refractories degrade less rapidly since such penetration is hindered. One aim for the current research is to seal the surfaces of these refractory materials by laser surface processing. In this way the bulk properties of the brick are retained, while the surface properties are improved. This paper reports on the results of an investigation to determine the optimum laser processing parameters that produce a zone of densified material containing few defects at the refractory surface. The high thermal stresses usually associated with laser treatment are often relieved by fracture of the laser-treated zone. However, by using a novel flame-assisted laser surface treatment, a reduction in thermal stress has been achieved, resulting in a crack-free, dense laser-treated zone. This treated zone should reduce or even eliminate the ingress of molten slags and gases, thus providing a reduced area for attack by corrosive species.