Surface treatment of alumina-based ceramics using combined laser sources

Alumina-based refractory materials are extensively used as linings in incinerators and furnaces. These materials are subject to molten salt corrosion and chemical degradation because of the existence of porosity and material inhomogeneity. Efforts to improve the performance of these materials have so far concentrated mainly on the optimisation of the manufacturing processes (e.g. producing denser refractory bricks) and in-service monitoring. Laser surface treatment has also been used to improve performance. The main problem identified with laser surface treatment is solidification cracking due to the generation of very large temperature gradients. The aim of this paper is to investigate the surface modification of alumina-based ceramics by using two combined laser sources in order to control the thermal gradients and cooling rates during processing so that crack formation can be eliminated. The material under investigation is 85% alumina refractory ceramic, used as lining material in incineration plants. The surface morphology and cross-section of the treated samples are analysed using optical and scanning electron microscopy (SEM) and compared with single laser beam treated samples.