Tribological behaviour of an electrochemical jet machined textured Al-Si automotive cylinder liner material

• Published in: Wear Vol. 376-377; no. PB; pp. 1611 - 1621
• Main Authors: Walker, J.C., Kamps, T.J., Lam, J.W., Mitchell-Smith, J., Clare, A.T.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-04-2017; Elsevier Science Ltd
• Subjects: Abrasion; Al-Si; Aluminum; Automotive; Automotive parts; Coefficient of friction; Cylinder liners; Dimpling; Electrochemical jet machining; Friction; Friction reduction; Lubrication; Machining; Nozzles; Silicon; Sliding; Sodium chloride; Sodium hydroxide; Submerging; Surface layers; Surface texturing; Texturing; Tribology; Wear; Weight reduction; Surface texturing; Electrochemical jet machining; Friction; Al-Si; Wear; Automotive
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2017.01.085

This paper investigates the use of Electrochemical Jet Machining to surface texture a hyper-eutectic Al-Si cylinder liner material. Samples were lapped to a 6μm finish followed by immersion in 1mol NaOH to expose the primary silicon colonies above the aluminium surface. Texturing was carried out using a NC system comprising of a fine gauge nozzle (cathode) jetting a solution of 2.3mol NaCl on the surface (anode) whilst applying a current density of 220A/cm2. An array of hemispherical dimples at 1.5mm spacing was created, with an average diameter of 420μm and depth of 40μm, corresponding to an ε ratio of 0.095. Lubricated reciprocating sliding was carried out at stroke length of 25mm in a bath of PAO (4cSt) against a 52100 cylinder of 6mm diameter and 16mm length. Sliding frequencies were incremented at 1Hz intervals between 1–15Hz at 50N load increments from 50-200N. Stribeck curves indicated a reduction of the friction coefficient due to texturing of up to 0.05 in the mixed lubrication regime, representing a decrease of 38.5%. Optical profilometry and SEM indicated that abrasion and formation of a surface tribo-layer was mitigated in regions of the Al-Si surface where textured features were present parallel to the sliding direction.
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•Electrochemical Jet Machining was used to texture a hyper-eutectic Al-Si alloy.•Textured features exhibited no evidence of edge burs or lips.•Friction coefficients were reduced by up to 38.5% as a result of the texturing.•Texturing enhanced debris removal, preventing formation of a surface tribo-layer.