Dry Sliding Friction and Wear Behaviour of an Electron Beam Melted Hypereutectic Al–Si Alloy

Abstract

The economic and environmental benefits of using light-weighting technology in automotive applications continue to attract attention for feasible commercial solutions. This study investigates the use of pulsed electron beam melting of a hypereutectic Al-Si alloy as a possible modification procedure for cylinder crankcase bore facing surfaces. Machined surfaces of an A390 alloy were subjected to five pulsed electron doses with an applied cathode potential between 16.5 and 36 kV. It was found that increasing beam accelerating voltages led to an initial decrease (1.4 lm R a ) but subsequent increase (4.0 lm R a ) in average surface roughness values associated with surface crater formation due to sub-surface melting and eruption. Surfaces were tested under dry sliding tribological conditions against 52100 bearing steel in a reciprocating geometry. Average dynamic friction coefficients were higher (0.9) compared to the untreated alloy surface (0.6) as a result of a greater degree of adhesion to the counterface. However, FIB cross sections of worn surfaces indicated that this activated an oxidative type wear process which ultimately led to the formation of a beneficial surface tribo-film on the EBM-treated surfaces, improving the specific wear rates by up to 66%.

Repair of EDM induced surface cracks by pulsed electron beam irradiation

“…For example, Gao et al (2007) reported improved unlubricated wear behaviour of magnesium alloy after electron beam treatment due to improved surface hardness, as well as the formation of a homogenous passivating layer at the surface, resulting in improved corrosion behaviour. Walker et al (2011) also demonstrated improved wear behaviour of hypereutectic Al-Si alloy under dry conditions. Zou et al (2010) have also shown similarly improved properties in electron beam treated 316L steel, whereby after 20 shots a homogenous protective film was formed, improving its corrosion resistance, and increased surface hardness explained improved dry wear behaviour.…”

“…The phenomenon of crater formation associated with pulsed electron beam irradiation has been reported in a variety of alloys. For example by Gao et al (2007) in magnesium alloy, as well as in aluminium-silicon alloys by Walker et al (2011) and tool steel by Zou et al (2007). Craters are thought to form due to melting which starts just below the surface.…”

“…In particular for steels, craters have been shown by Zou et al to form at the location of Cr 7 C 3 carbides in tool steel (Zou et al, 2009) and at MnS inclusions in 316L stainless steel (Zou et al, 2010). For Al-Si based alloys they have been shown to occur at sites of primary silicon particles (Walker et al, 2011). The occurrence of craters is important to understand since work by Zhang et al has shown that they are sensitive to corrosion pitting, particularly if they contain holes or cracks at the surface (Zhang et al, 2006).…”

A review of hypereutectic aluminum piston materials

“…Another modification of hypereutectic AlSi alloys is possible by electron beam melting of their surface. In [35] EBM is applied on A390 hypereutectic (16-18%Si) AlSi alloy. More about this process can be found in the mentioned literature.…”

Amorphous layer formation in Al86.0Co7.6Ce6.4 glass-forming alloy by large-area electron beam irradiation

“…Over the past decade, LAEB has been applied to polish and improve the corrosion behaviour of mould surfaces [17][18][19], improve surface hardness in steels and magnesium alloys [20], as well as the wear resistance of Al-Si alloys [21,22]. More relevant to the current work, Guan et al [23] have observed localised amorphisation in a simple low-carbon steel by this process, giving evidence that the high-cooling rates associated with this technique can be applied for amorphous layer preparation.…”