Synthesis and cladding of Al2O3 ceramic coatings on steel substrates by a laser controlled thermite reaction

After being adequately diluted through the addition of Ni and SiO2, the thermite reaction can be used to clad an Al2O3 based ceramic coating on a steel substrate by laser controlled reactive synthesis with a lower energy input. The dilution rate is the key factor influencing the cladding process. Only when the dilution rate is adequate, the reaction becomes less explosive and a continuous and smooth clad can be obtained. Reasonable addition of diluents and additives should guarantee the adiabatic temperature of the reaction to be lower than 1800 K. The laser energy input is another factor influencing the cladding process. With the rise of the average laser energy input, the width of the final clad and mixing rate of substrate to the clad increase. The addition of additives, especially SiO2 make a great contribution to the improvement of the clad quality. In this case, the clad is continuous, homogeneous, with few defects and metallurgical bonding to the substrate.