Abstract
The effect of temperature and air pressure at the supersonic nozzle inlet, as well as the distance from the nozzle outlet to the surface of the substrate (stand-of-distance) on the powder usage rate of nickel-based powder in low pressure cold gas-dynamic spraying (inlet pressure up to 1.0 MPa) was analyzed. One of the most important parameters characterizing the deposition efficiency of the spraying process is the powder usage rate. This parameter is the ratio of the mass of the coating to the mass of the powder used to obtain this one. For the process of cold gas-dynamic spraying, implemented on the equipment using air pressure up to 1.0 MPa, the main disadvantage is the relatively low-powder usage rate. To increase it (but not limited to it), a ceramic component, such as alumina Al2O3, is added to pure metal powders. In this study a nickel-based powder mixture, in which the content of Al2O3 powder is about 10% mass., was used. Titanium alloy plates BT9 were used as the substrate material. Based on the multifactor planning of the experiment, the effect of the complex parameters of the low-pressure cold gas-dynamic spraying on the powder usage rate was studied. After the coating deposition according to the matrix of the experiment, the samples with coatings were weighed. According to the known mass of the samples before spraying and the increase in their mass, the powder usage rate was calculated. From the analysis of the obtained statistical data, the dependence of the effect of the complex parameters of the deposition process on the powder usage rate was developed. The maximum value of the powder usage rate were obtained up to 35 %. It was confirmed that the air temperature at the nozzle inlet has the greatest effect on the above-mentioned parameter. The explanation of this is the increase in gas flow temperature and velocity, and as a result, the increase in the velocity and temperature of the powder particles in this flow. Higher values of the velocity and temperature of the particles lead to more intense plastic deformation of particles during impact with the substrate and their adhesion to it.
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