Simultaneous optimization of flame spraying process parameters for high quality molybdenum coatings using Taguchi methods

Flame-sprayed molybdenum coatings are extensively used in industrial applications to enhance the performance of engineering components such as pistons, piston rings and shafts. Improved resistance to thermal degradation, corrosion and wear can be achieved. In all these applications, the performance of the coating is dependent upon its cohesive and adhesive strengths, which are affected by the spraying process parameters employed during the coating deposition process. In the present study, an attempt is made to produce high quality coatings by optimizing the spraying process parameters using Taguchi techniques. Experiments are conducted using ASTM specimens to produce coatings which have high cohesive strengths. A new test specimen is proposed by modifying the ASTM specimen to give a fracture mechanics specimen which can quantify the adhesive strength of the coating. Microstructural studies are conducted on the sprayed coatings and the changes in the microstructure with different spraying conditions are correlated with the strength variations of the coating.