External Ballistics of Powder Under Detonation Spraying

The effect of spraying distance and orientation of the substrate on formation of metal coatings by detonation spraying is studied. A significant influence of the processes outside the barrel on characteristics of the spraying process and properties of the resulting coatings is found.
General regularities of non-monotone dependence of deposition efficiency on spraying distance are observed for metals with strongly different characteristics such as aluminium, copper, titanium and steel. In particular, the highest deposition efficiency is achieved at distances more than ten barrel calibres, which shows that, in spite of the pulsed character of the detonation spraying process, influence of detonation products on sprayed particles is maintained even outside the barrel.
Numerical calculations of acceleration and heating inside the barrel of particles of the materials studied are performed. Based on the results obtained, an estimate of the process outside the barrel is proposed.
Optimal spraying process parameters allowing 65-80% deposition efficiency are defined and experimentally validated for all the materials studied.