Effect of atmospheric plasma spraying parameters on porosity level of alumina coatings

Alumina coating was deposited on AZ31B magnesium alloy using atmospheric plasma spraying process by varying parameters such as power, stand-off distance and powder feedrate. The porosity level of alumina coatings were evaluated by the digital image analysis method. An attempt was also made to develop an empirical relationship to predict the porosity level of alumina coatings. Three factors five level central composite rotatable design matrix was used to minimise the number of experimental conditions. Response surface methodology was used to develop the relationship. The developed relationship can be effectively used to predict the porosity level of alumina coatings at 95% confidence level. The results indicate that the input power has the greatest influence on porosity level of the coatings, followed by stand-off distance and powder feedrate.