Abstract
Even though cold spraying is well established today, the handling of some materials, as for example nickel, is still challenging because of nozzle clogging at higher process gas temperatures. Due to these process limitations in the past, it was not possible to produce coatings of sufficiently high quality. These problems can be solved by nozzle modifications. By a more effective nozzle cooling system, nozzle clogging during cold spraying of nickel can be avoided. This enables the use of high-end spray conditions, attainable by a modified cold spray gun heating system. For the presented study, the coatings were produced by varying the spray parameters up to a process gas temperature of 1000 °C at a pressure of 5 MPa with a gas flow of about 160 m3/h - conditions that were not within reach in cold spraying so far. Coating microstructures are nearly fully dense, with negligible porosity below 0.1%. The coatings processed under these high-end parameters show high tensile strength of 570 MPa, similar to that of highly deformed bulk material and a low hardness of 200 HVIT similar to that of pure nickel. The results demonstrate that the quality of cold-sprayed nickel coatings significantly improves with higher process gas temperatures and pressures, pushing cold spraying to new limits. This may also apply to other high-strength metals and alloys, opening the opportunity to meet the quality requirements for many new applications.
