Effect of processing parameters of electron beam melting machine on properties of Ti-6Al-4V parts

Abstract

Purpose This paper aims to study the effect of processing parameters of an electron beam melting (EBM) machine on the surface roughness, critical pitting temperature and density of Ti-6Al-4V parts produced from the EBM machine. Design/methodology/approach In this study, statistically designed experiments were used to manufacture Ti-6Al-4V samples in the EBM machine under different process parameters of beam current, beam speed and offset focus. Surface roughness was measured for as-built samples using a 3D profilometer. Then, a potentiostatic test was conducted under 2.40 V vs saturated calomel electrode to determine the critical pitting temperature (CPT) in 3.5 per cent mass NaCl solution for the samples of different processing parameters. Next, density was measured for these samples. Finally, model equations were established to relate EBM’s process parameters to measured properties of surface roughness, CPT and density. Findings Results showed that offset focus had the main influence on surface roughness more than the beam current and the beam speed. Changing processing parameters did not affect corrosion behavior of EBM Ti-6Al-4V as CPT did not vary widely, although a slight effect on CPT values obtained from the beam current and the beam speed. Density was greatly affected by the offset focus more than the other parameters. It can be concluded that uniform and precise measurements of roughness and density are not achievable through this machine; only a range of these properties can be attained. Originality/value EBM machine produces 3D parts in a layer-based building process under high temperature and vacuum atmosphere. Due to the manufacturing technique and conditions, the resulting object has irregularities on the exterior surface and voids that are formed within the part, both of which affect samples’ properties like surface roughness, CPT and density. This study established model equations that can relate parts’ properties to processing parameters so that parts of specific properties are obtained to fit the application they are used for. For each property, ANOVA fits vs linear energy were also obtained.

Processing windows for Ti-6Al-4V fabricated by selective electron beam melting with improved beam focus and different scan line spacings

“…However, they also allow for significantly lower residual stresses compared to parts produced by laser based methods such as SLM (Shipley et al , 2018). Resulting material properties have been found to be highly influenced by interdepending processing parameters such as energy density, beam power and scan speed, which is valid for both laser and electron beam melting (Everhart et al , 2016; Shipley et al , 2018; Juechter et al , 2014; Abdeen and Palmer, 2016; Al-Bermani et al , 2010; Facchini et al , 2009; Morita et al , 2017; Puebla et al , 2012; Scharowsky et al , 2017). An independence of mechanical properties from density of the resulting part has also been reported, while scan length of individual melt lines, i.e.…”

“…Beam power P beam and scan speed v scan were varied between 20 and 3000 W and 0.2 and 52.5 m s −1 , respectively. In literature, the values reported for generation of good samples ranged from 300 to 1600 W at 0.8 to 20 m s −1 on Arcam S12 (Al-Bermani et al , 2010; Scharowsky et al , 2017; Morita et al , 2017), Arcam A2 (Abdeen and Palmer, 2016; Puebla et al , 2012) and Arcam A2x machines (Kirchner et al , 2015). The scan line spacing h s was set to 100, 50 and 20 µm.…”

Additive Manufacturing of Titanium Alloys for Orthopedic Applications: A Materials Science Viewpoint

“…It is important to note that the effects of these parameters are interrelated. The ratio between beam current (and intensity) and scanning velocity is important in considering the final properties of the part [83,99] . Ideally, a low scanning velocity should be paired with a moderately high beam current to produce a dense and flat part with pores at the outer layers [87] .…”

Defect formation in EBM parts built at different orientation

“…This has led to the widespread impression that the EBM machine often produces near-net-shape parts that require a subsequent processing treatment. Dimensional inaccuracy and high surface roughness also relate to properties, such as the wear rate and friction, which directly affect the lifetime of the product [4,5,6]. [7] indicate that it is very challenging to obtain high dimensional accuracy EBM and other AM built parts.…”