Energy absorption during pulsed electron beam spot melting of 304 stainless steel: Monte-Carlo simulations and in-situ temperature measurements

The absorption coefficient during pulsed, conduction-mode electron beam spot melting of 304 stainless steel was measured at different combinations of accelerating voltage [60,80] kV, beam current [10,15,20] mA, pulse length [0.6-12] mS and beam inclination angle [0, 15, 35, 55, 65]°. Ignoring evaporative and radiative heat loss, the absorption coefficient was determined directly by fitting in-situ thermocouple measurements to an analytical function, with an average adjusted R-square fit parameter of 0.9996 over the 103 measurements. The absorption coefficient was found to be insensitive to both beam current and accelerating voltage, but decreased with increasing inclination angle. Measurements are compared to estimates generated from Monte-Carlo electron trajectory simulations using the CASINO software, with good agreement for all process parameter combinations, experimentally demonstrating the capability of Monte-Carlo methods to estimate local electron beam heat transfer.