Combustion properties of titanium alloy powder in ALM processes: Ti6Al4V

The Ti6Al4V powder alloy combustion is studied in order to define dust explosion parameters for industrial safety and combustion mechanism for scientific analysis. No results exist in literature of dust explosion concerning titanium alloy like Ti6Al4V. Three different powders with different average particles size (around 13 mu m, 26 mu m and 55 mu m) were studied. The interest comes from its wide use in metallurgy, especially for aeronautical, dental and defense applications. This paper reports the minimum ignition energy (MIE) of the alloy powders as a function of the concentrations. Hartmann tube apparatus was used in this way. Results can be synthetized as: 3.5 mJ for 13 mu m, 4 mJ for 26 mu m and 357 mJ for 55 mu m particle size. When comparing the values of MIE for pure titanium (Ti) and pure aluminum (Al) powders, the alloy sensibility is near pure Ti. Severity parameters and temperature measured by IR pyrometry were investigated during 20 L spherical explosion vessel tests. Results shown 6 bar overpressure and rate of pressure rise at 546 and 474 bar/s for 13 and 26 mu m respectively. In case of the powders average diameter around 55 mu m, ignition occurred in only one condition: 1500 g/m(3). Temperatures were measured during explosion following two different scales: versus time and versus concentration.