R. Knight, R. A. Cairncross, Drexel University, Philadelphia, PA; M. Ivosevic, Resodyn Corporation, Butte, MT
Numerical predictions and experimental observations have been correlated to improve the qualitative understanding of the degree of thermal degradation occurring during the HVOF spray deposition of Nylon-11. Particle residence time (< 1 ms) in the HVOF jet was insufficient for significant decomposition and/or mass loss of Nylon-11 but was sufficient to produce noticeable discoloration (yellowing) of smaller powder particles with a mean particle size of 30 mm. Experimental observations showed this to be the case even though numerical predictions indicated that the temperature of a 30 mm diameter particle should be considerably higher than the upper degradation limit of Nylon-11. Initial thermal oxidation of Nylon-11 promotes the formation of carbon-carbon double bonds that strongly absorb in the visible spectrum even at concentrations of parts per million levels resulting in discoloration of the Nylon.
Numerical predictions and experimental observations have been correlated to improve the qualitative understanding of the degree of thermal degradation occurring during the HVOF spray deposition of Nylon-11. Particle residence time (< 1 ms) in the HVOF jet was insufficient for significant decomposition and/or mass loss of Nylon-11 but was sufficient to produce noticeable discoloration (yellowing) of smaller powder particles with a mean particle size of 30 mm. Experimental observations showed this to be the case even though numerical predictions indicated that the temperature of a 30 mm diameter particle should be considerably higher than the upper degradation limit of Nylon-11. Initial thermal oxidation of Nylon-11 promotes the formation of carbon-carbon double bonds that strongly absorb in the visible spectrum even at concentrations of parts per million levels resulting in discoloration of the Nylon.
