Wear Behavior of AlSi10Mg Alloy Produced by Laser‐Based Powder Bed Fusion and Gravity Casting

Abstract

Herein, the sliding wear behavior of AlSi10Mg samples realized using laser‐based powder bed fusion (LPBF) is investigated via pin‐on‐disc (PoD) tests, before and after T6 heat treatment. The changes in the microstructure, density, and hardness induced by heat treatment are correlated with the tribological behavior of the alloy. Furthermore, short wear tests are conducted and the resulting wear tracks are investigated through scanning electron microscopy (SEM), equipped with an energy‐dispersive spectroscopy (EDS) microprobe to elucidate how the wear mechanisms evolve with sliding distance. For comparison, gravity cast (GC) AlSi10Mg samples are also characterized and tested. The as‐built additive manufacturing (AM) sample exhibits the lowest wear rate and coefficient of friction because of its high hardness and relative density, whereas the heat‐treated sample shows the worst behavior in comparison with the GC samples. The results suggest a significant influence of porosity on the wear behavior of AM alloys.

A critical review on the effects of process-induced porosity on the mechanical properties of alloys fabricated by laser powder bed fusion

“…material, though pore closure could be beneficial for corrosion resistance. If heat treatments are necessary for LPBF AlSi10Mg, then HIP might have the added benefit of restricting pore growth during heat treatment, a phenomenon commonly reported for this alloy [20][21][22].…”

“…Argued that even if all pores could be removed, the elongated grain morphology would still promote cavitation-induced crack propagation [244] 316L Particle Erosion LPBF 316L performed worse than wrought 316L regardless of impingement angle Poor performance generally attributed to porosity [79] AlSi10Mg Sliding Sub-surface LoF pore orientation can affect crack propagation leading to delamination Surface LoF pore orientation can alter the actual contact area and thus, the contact stresses The influence of porosity is also affected by sliding test conditions and microstructure [21] AlSi10Mg Sliding T6 treatment can cause an increase in porosity, resulting in LPBF AlSi10Mg performing worse than cast AlSI10Mg despite similar hardness [245] AlSi10Mg Fretting Fatigue…”

“…Even though porosity formation can be greatly minimized by choosing optimal LPBF parameters, it must be emphasized that there is no guarantee that using the same set of processing parameters would always result in the same type(s) and amount of pores since LPBF production is known to suffer from poor repeatability [15] and porosity distribution can also be affected by other factors such as part geometry [16,17], feedstock powder particle size [18], powder bed temperature [19], heat treatment (which can cause gas pore to enlarge) [20][21][22], and gas flow behavior [23]. In fact, pores may not necessarily be uniformly distributed within a single part [24] and LPBF parameters optimized for part density often involve an undesirable trade-off with production speed [25].…”

Nanoprecipitates enhanced wear resistance of laser powder bed fusion-processed high-strength Al−Cu−Mg−Si−Ti alloy

“…Figures 10 (a) and (b) display the wear mechanism of the sample at a slight applied load of 2.1 N. It is well known that Al is extremely active to oxygen and often undergoes continuous oxidation due to the limited solubility of oxygen in Al and low equilibrium partial pressure of oxygen in the oxidation reaction of Al [1]. Therefore, coupled with the large amount of heat generation during the wear process, a surface oxidation reaction is inevitable [42,43]. Therefore, at the beginning stage of the wear process, the Al oxide layer forms and adheres to the worn surface.…”

“…Moreover, the dominant wear mechanism transforms from abrasive wear for an applied load of 2.1 N to slight delamination and abrasive wear for an applied load of 10 N. When the applied load reaches 24 N, the wear mechanism is controlled by severe delamination and abrasive wear, which accelerates the wear process and leads to a great increase in the wear rate. For the heattreated Al-Cu-Mg-Si-Ti part, a high number density of nanosized S' and Q' with larger sizes compared to the as-built part precipitates during the aging process, as shown in the magnified images in figure 10, which hinders the movement of dislocations and thus significantly increases the microhardness [42,48]. The high microhardness of the aging heat-treated sample offers great resistance to the penetration behavior of the counterpart ball and to the scratching of oxide abrasives on the worn surface [49].…”