Statistical approach for minimizing cracks in combined flame spraying and laser surface modification of refractory ceramics

Combined flame and CO2 laser spraying for surface modification of 20 wt.% Cr2O3–80 wt.% Al2O3 has been developed for improved surface performance of alumina-based refractory bricks. In this paper, the crack length per unit surface area and crack density of single treated tracks with respect to the three process parameters: laser irradiation intensity, powder feed rate and workpiece traverse velocity, have been investigated by employing a statistical approach involving statistical experiment design and regression analysis. It was found that the present statistical approach was effective for investigating the role of the process parameters on the crack length per unit surface area. Reducing both the powder feed rate and the workpiece traverse velocity could reduce the occurrence of cracks in the treated tracks. The former corresponded to decreasing the α-Al2O3 content in the treated tracks, and the latter to decreasing the cooling and solidifying rate of the melt pool.