Wear 260 (2006) 339–344 Effects and mechanisms in minimal quantity lubrication machining of an aluminum alloy F. Itoigawa a,∗ , T.H.C. Childs b , T. Nakamura a , W. Belluco c a Department of Mechanical Engineering, Nagoya Institute of Technology, Gokiso, Nagoya 466-8555, Japan b School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK c Renault, Powertrain Engineering Division, Advanced Process Engineering, 67, rue des bons raisins, 92508 Rueil Malmaison Cedex, France Received 8 November 2004; received in revised form 8 March 2005; accepted 28 March 2005 Available online 8 August 2005 Abstract Effects and mechanisms in minimal quantity lubrication are investigated by use of an intermittent turning process. Especially a difference between minimal quantity lubrication (MQL) and MQL with water is inspected in detail to elucidate boundary film behaviour on the rake face. In order to obtain a good cutting performance by MQL it is considered that two things are needed: (1) an appropriate lubricant, such as a synthetic ester, to form a strong boundary film and (2) a chilling effect to sustain strength of the boundary film. © 2005 Elsevier B.V. All rights reserved. Keywords: Minimal quantity lubrication; Oil film on water; PCD tool; Aluminum alloy; Intermittent cutting; Boundary lubrication 1. Introduction Enormous efforts to reduce the use of lubricant in metal cutting are being made from the viewpoint of cost, ecological and human health issues [1–4]. Minimal quantity lubrication (MQL) can be considered as one of the solutions to reduce the amount of lubricant and is being studied for practical appli- cations, especially aluminum alloy cutting. Its application scope is, however, uncertain because the MQL lubrication mechanism has not been sufficiently elucidated. Recently, by model experiments, Wakabayashi et al. suggested that ester supplied onto a rake face of a tool decomposes to carboxylic acid and alcohol and its carboxylic acid forms a chemisorbed film with lubricity [5]. In actual conditions with high machining load, however, existence of this kind of bound- ary film is uncertain. Therefore an investigation into the lubrication mechanism of MQL in actual conditions must be essential. Recently two of the authors proposed a new type of MQL in which a minimal amount of oil is supplied into a cutting ∗ Corresponding author. Tel.: +81 52 735 5356; fax: +81 52 735 5356. E-mail address: itoigawa@tribo.mech.nitech.ac.jp (F. Itoigawa). point, carried by and mixed with water droplets [6,7]. By this method the machining force in a milling process can be reduced, more than by the supply of the same amount of oil droplets alone, and thermal expansion is also suppressed. These facts are very interesting and seem to be important for elucidating the effect and lubrication mechanism by the only small amount of oil in MQL. On the other hand there are many reports, which indicate that MQL in an end-milling process is more effective than in a continuous turning process [8,9]. This is considered to be because lubricant can reach the tool face more easily in milling than turning. In order to elucidate the MQL lubri- cation mechanism, the details of the friction characteristic between chip and tool and its change with sliding length should be investigated. It is, however, difficult to estimate the friction characteristics in an actual end-milling process. In this study intermittent turning is employed instead of the end-milling process. In this situation cutting can be approx- imately modeled as orthogonal cutting. Experiments have been conducted in this way with various lubrication methods including MQL and MQL with water. The results obtained have been used to consider what are the MQL lubrication mechanisms. 0043-1648/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2005.03.035