The physical state of each individual droplet prior to collision is the most critical condition of 
the process. Experiences show, that semi — liquid droplets have the highest sticking 
probability. 
Small droplets are usually completely solidified forming porous layers due to a less dense 
packing factor. Moreover, if no liquid is left, droplets just bounce off the surface and do not 
contribute to the deposition rate at all. 
In contrast, large droplets may still be fully liquid. If they strike the surface of the billet, the 
high centrifugal forces cause a loss due to splashing. 
As a consequence to the outlined boundary conditions, the distance between the origin and 
deposition must be kept constant. 
— Spr hkompakticren gg 
wieland-Werke AG fr 
Continuous cast Spray formed 
A Wieland 
Figure 4: Macrostructures of billet cross - sections, alloy Cu Cr Zr, left — continuous cast, right — spray formed 
The small volume of each droplet is quenched rapidly during the deposition. The resulting 
microstructure is homogeneous and virtually free of segregations ( Fig.4 ). The grain size of 
the primary structure is in the order of the average droplet size ( about 60 pum ). These 
characteristics of the microstructure and the fine distribution of the elements and the phases in 
the microstructure are responsible for the optimal mechanical and tribological properties and 
the almost homogeneous distribution of the properties in the semifinished product. 
The billet can be further processed due to the customer specifications ( e.g. hot working, heat 
treatment, ). 
3. Characteristics of the base material and experimental procedures 
Chemical composition of the investigated alloy ( in mass - % ): 
14.3 % Al, 4.6% Fe, 2.2% Mn, 2.3% Co, balance Cu. 
Hardness of the spray formed alloy: 
HB 2.5/187.5=395 
5 che SDraV 
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