Machining performance of TiN coatings incorporating indium as a solid lubricant Canan G. Guleryuz a , James E. Krzanowski a, ⁎, Stephen C. Veldhuis b , German S. Fox-Rabinovich b a University of New Hampshire, Mechanical Engineering Dept., Durham, NH 03824, USA b Department of Mechanical Engineering and Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada L8S 4L7 abstract article info Article history: Received 26 September 2008 Accepted in revised form 21 April 2009 Available online 24 April 2009 Keywords: Sputtering Machining Indium Titanium Nitride Photoelectron Spectroscopy The machining and wear performance of TiN-coated and patterned carbide inserts incorporating indium as a solid lubricant are reported in this study. Cutting tests were conducted by turning hardened 4340 steel in both lubricated and dry conditions. During turning, periodic flank wear measurements were made. The chips formed during cutting were examined by scanning electron microscopy, as the condition of the chip reflects the conditions obtained during machining. Inserts subject to dry machining were also examined using optical microscopy and X-ray photoelectron spectroscopy to determine the extent of damage on the rake surface as well as the degree of material transfer. The results showed indium to be effective in reducing flank wear during lubricated machining, but little additional benefit of patterning was observed. For dry machining, some degree of improvement was noted in the patterned sample, but the degree of lubricity brought about by the indium coating was not sufficient and the overall flank wear was higher than the lubricated tests. However, the wear and damage on the rake surface along the path of the chip was reduced by the presence of the In-containing microreservoirs. An additional test was conducted using an instrument that simulates temperature effects during machining, and it was found that the lubricity achieved by In coatings is lost above 450 °C. These results suggest that the use of indium is limited to below this temperature, and above this temperature transforms to a less lubricious indium oxide. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Metal cutting processes have traditionally made extensive use of lubricating fluids. Recently, the economical and environmental disadvan- tages of using these fluids have become more pronounced. Their share in machining costs is high and management of the waste has become complex due to the environmental regulations. Elimination of the cutting fluids (dry machining) has been investigated as a potential solution and numerous research studies have been conducted, focusing on improving tool materials, tool coatings and/or finding tool geometries appropriate to conditions for dry machining [1–3]. In particular, improved tool coatings are sought that would help to negate the loss of some of the facilities provided by cutting fluids, namely cooling, lubricating and flushing the chips [1,2]. Coatings for cutting tools and other applications that require good wear resistance and low friction have observed steady advances for the last several decades, evolving from single layer/single phase coatings to multilayer/multiphase, gradient, superlattice, and composite coatings [4–7]. Composite coatings are multiphase/multiconstituent coatings that are tailored to combine the beneficial properties of several phases, such as combining a hard phase with a soft and lubricious phase. Examples of composite coatings based on natural phase separation during deposition include WC/Ag and TiC/Ag [4], CrN/Ag [5], DLC/Ag [6] and yttria-stabilized zirconia with gold [7]. While natural phase separation can occur in highly immiscible systems, the formation of amorphous or alloyed films instead can be a limitation to achieving the desired composite microstructures [8]. Recent efforts have been made to artificially create three dimensionally structured composite coatings for tribological applications. For example, Voevodin et al. [9] used a laser to cut a circular groove matching the center of the wear track in a functional gradient Ti–TiC–DLC coating, and then deposited MoS 2 in this groove. The purpose of this process was to provide a means for storage and replenishment of the solid lubricant. Pin-on-disk tests showed that this coating had a longer wear life than either the constituents alone or a MoS 2 /Ti–TiC–DLC bilayer coating. In their more recent work, Voevodin and Zabinski [10] studied the effect of laser drilled 10 or 20 μm-sized-holes on the wear life of a TiCN coating. MoS 2 was applied to the surface of the hard coating after laser processing by either burnishing or magnetron sputtering. Several different geometries (area coverage and reservoir size) were examined in order to determine the optimum structure. The results showed that the reservoirs helped to improve the wear life by as much as one order of magnitude compared to the coatings without reservoirs. It was also found an optimum area coverage near 10% for their tribological system. Recently, we have explored a new approach for creating composite coatings in which microscopic beads are placed on the substrate and act as placeholders for microreservoir formation [11,12]. This approach is reviewed in detail in the following section. Results obtained with TiN/graphite composite Surface & Coatings Technology 203 (2009) 3370–3376 ⁎ Corresponding author. E-mail address: jamesk@cisunix.unh.edu (J.E. Krzanowski). 0257-8972/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2009.04.024 Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat