The size and shape of individual particles are essential characteristics to control their behavior during spraying. Thanks to recently available technology in powder image analysis, this paper investigates the correlation between the geometric properties of several thousands of particles and their flowability (Hall flowmeter) and apparent density (Scott volumeter). Four different chromium carbide Cr 3 C 2 -NiCr 75/25 powders used for HVOF wear / oxidation resistant coatings are studied. The coating quality obtained for each powder by the HVOF spraying process is further investigated using metallographic image analysis.

Ni+Al, Ti+Al, NiCr+AI, and Cr+Al powders react exothermically in the heat zone of thermal spraying systems. Whether such reactions occur between aluminum and superalloy powders is the underlying question of this study. This paper describes composites of this nature and their sprayability to form adherent, metallurgically bonded deposits. Through parametric manipulation, coatings can be produced with a range of properties from dense to open (porous/abradable) structures. The paper also shows how seed particles can be clad with aluminum and sprayed to predictable property limits.

The demand for highly continuous thermal spray deposition processing to gain manufacturing efficiency and enhanced control of deposition microstructure has driven the search for powder feedstocks that exhibit uniform flow behavior in pneumatic feeding devices even at low carrier gas flow ratios. This paper compares the continuous powder feeding characteristics of one type of feeding device for two different powder alloys fabricated by a representative set of powder processing methods, including spray dried, fused (cast) and crushed, and inert gas atomized. Powders were fabricated by both commercial vendors and Ames Laboratory processing equipment. The powder mass flow rate was found to depend directly on the apparent density of a specific powder type instead of the dry powder flowability, as initially expected.