Abstract
Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that facilitates the production of metal parts by selectively melting areas in layers of metal powder. The electron beam melting process is conducted in a vacuum chamber environment regulated with helium (He) at a pressure on the scale of 10−3 mbar. One of the disadvantages of vacuum environments is the effect of vapor pressure on volatile materials: indeed, elements in the pre-alloyed powder with high vapor pressure are at risk of evaporation. Increasing the He pressure in the process can improve the thermodynamic stability of the pre-alloyed components and decrease the composition volatility of the solid. However, increasing the pressure can also attenuate the electrons and consequently reduce the energy deposition efficiency. While it is generally assumed that the efficiency of the process is 90%, to date no studies have verified this. In this study, Monte Carlo simulations and detailed thermal experiments were conducted utilizing EGS5 and an Arcam Q20+ machine. The results reveal that increasing the gas pressure in the vacuum chamber by one order of magnitude (from 10−3 mbar to 10−2 mbar) did not significantly reduce the energy deposition efficiency (less than 1.5%). The increase in gas pressure will enable the melting of alloys with high vapor pressure elements in the future.
Highlights
Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology [1,2] that facilitates the fabrication of three-dimensional near-net-shaped parts by spreading successive layers of metal powder on a powder bed-chamber and selectively melting areas in them [3,4]
This study presents calculations of the electrons’ energy deposition efficiency to the metal alloy using EGS5 simulations, which were validated by thermal experiments performed using an Arcam Q20+ machine (Arcam, Mölndal, Sweden)
The EBM process is conducted in a vacuum chamber environment regulated with He at a pressure of 10−3 mbar
Summary
Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology [1,2] that facilitates the fabrication of three-dimensional near-net-shaped parts by spreading successive layers of metal powder on a powder bed-chamber and selectively melting areas in them [3,4]. The process efficiency in a powder bed EBM can be affected by many variables, and this has not yet been verified by studies It is well-known that EB possesses high penetration ability [19], previous studies have used CASINO [20] Monte Carlo (MC) to develop heat source models and determine the maximum penetration depth of the electron [21,22]. This study presents calculations of the electrons’ energy deposition efficiency to the metal alloy using EGS5 simulations, which were validated by thermal experiments performed using an Arcam Q20+ machine (Arcam, Mölndal, Sweden). It aimed to discover the optimal gas pressure point to decrease the composition volatility of the melt pool while not significantly attenuating the electrons and preserving the energy deposition efficiency
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