This paper investigates a universal law of the relationship between the particle diameter and material density, to provide almost identical particle velocity distribution for two or more spray particles with different material density, by using onedimensional calculation. The spray materials selected in this investigation were Ti, Cu and WC-12Co. The universal law was constructed through the calculation of cold-sprayed particle velocities. Then, the validity of the universal law was verified by the calculations of particle velocity of warm spray and HVOF thermal spray. Special attention was paid to the particle velocity outside the thermal spray guns. The calculated results reveal that 1) when the particle diameter d_p is selected for an arbitrary material density ρ_p against a set of reference diameter and material density based on the proposed universal law, the particle velocity outside the thermal spray gun becomes almost identical to the velocity of the reference particle within the accuracy of around ±6% in the range of 1,700 < d_pρ_p^0.72 < 30,000 μm(kg/m₃)_0.72, 2) the proposed universal law can be applicable to thecold spray, warm spray and HVOF thermal spray.

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The authors investigated the microstructure and phase about the self-fluxed alloy sprayed coating re-melted by fusing treatment, and compared the microstructure, precipitates and mechanical properties of self-fluxed alloy sprayed coating re-melted by high-frequency induction heating with those by gas-torch flame used. The results obtained are as follows.(1)The particle in the self-fluxed alloy sprayed coating re-melted was Ni solid solution. The matrix in the self-fluxed alloy sprayed coating re-melted was the eutectic structure consisted of Ni phase and Ni₃B phase, and the matrix became hard because of the precipitation of Ni₃B phase.(2)It was clear that the microstructure and mechanical properties of self-fluxed alloy sprayed coating re-melted by highfrequency induction heating were the same as those by gas-torch flame. So it was judged that the fusing treatment by high frequency induction heating was valid.

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