Wear 266 (2009) 865–872 Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear Sliding wear behaviour of T6 treated A356–TiB 2 in-situ composites A. Mandal a,∗ , B.S. Murty b , M. Chakraborty a a Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, West Bengal, India b Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Madras, Chennai 600036, Tamil Nadu, India article info Article history: Received 12 July 2007 Received in revised form 17 November 2008 Accepted 2 December 2008 Available online 7 December 2008 Keywords: In-situ composites TiB2 Dry sliding wear Wear resistance Wear debris abstract Dry sliding wear behaviour of A356–TiB 2 composites in T6 condition was tested using a pin-on-disc wear testing machine. The composites were prepared by the reaction of a mixture of K 2 TiF 6 and KBF 4 salts with molten alloy. The wear tests were conducted at normal loads of 19.6–78.4 N and a sliding speed of 1 ms -1 . A detailed SEM study of wear surface and debris was carried out to substantiate the wear results. The results indicate that wear rate of the composites is a strong function of TiB 2 content rather than overall hardness of the composite. The role of Si and TiB 2 particles towards the overall mechanism has been discussed. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The aluminium alloys for wear resistance applications are based on Al–Si system. It is this silicon phase that contributes to very good wear resistance of these alloys. However, the role of silicon towards wear resistance needs further investigation [1]. The wear resistance of these alloys can be further increased by addition of reinforce- ments, either ex-situ or in-situ [2]. A good amount of work has been done on commercial A356 alloy dispersed with SiC particles [3–6]. But a few literatures are available on the wear behaviour of Al-based composites reinforced with in-situ particles, particularly TiB 2 [7–10]. All the investigators above have advocated the benefi- cial effect of in-situ TiB 2 particles. Nevertheless, they also reported that wear behaviour the composites deteriorated with the increase in the amount of in-situ particles such as Al 3 Ti [7–9]. Caracostas et al. [10] in their work involving two different sizes of TiB 2 particles, reported that for a fine particle size distribution of TiB 2 the third body wear was minimum. In spite of volumes of literature pertaining to the sliding wear behaviour of various MMCs, work on A356 alloy reinforced with in-situ TiB 2 particles (generated via the reaction of K 2 TiF 6 and KBF 4 salts) is scarce [11]. Deuis et al. [2] have reviewed the wear behaviour of Al–Si alloys and other Al-based composites and sug- gested that effect of in-situ TiB 2 , TiC and SiO 2 particles towards the wear behaviour needs further investigation. ∗ Corresponding author. Current address: Worcester Polytechnic Institute, MA 01609 USA. Tel.: +1 508 831 6503; fax: +1 508 831 5993. E-mail address: animesh.mandal@gmail.com (A. Mandal). The present paper reports the dry sliding wear behaviour of T6 treated A356–TiB 2 MMCs synthesised by an in-situ technique. A microstructure-based explanation was attempted to account for the variation in wear rates and coefficient of friction of the composites. The study of wear surfaces and debris provided an insight into the possible wear mechanism. 2. Experimental details The commercial A356 alloy was reinforced with different amounts of TiB 2 particles (2.5, 5, 7.5, 10wt.%) via an in-situ reac- tion of molten alloy with K 2 TiF 6 and KBF 4 salt mixture. The details of process parameters for the synthesis of composites and their peak aged conditions are mentioned elsewhere [12]. The synthesis technique of the composites was similar to that reported in earlier works [13]. The dry sliding wear tests were conducted on a pin- on-disc wear testing machine (Model: TR-20, DUCOM) according to the ASTM G99-04 Standard. The cylindrical pins (8 mm diameter and 25 mm height) of the alloy/composite were used as test mate- rial. The hardened chromium steel (R c 64) was used as the counter face material. The wear tests were carried out at different loads (19.6, 39.2, 58.8 and 78.4N), which correspond to nominal contact stress of 0.39, 0.78, 1.17 and 1.56 MPa, respectively. The sliding speed and sliding distance was maintained at 1 ms -1 (corresponding to disc speed of 240 rpm) and 1800 m, respectively for all the tests. The track radius was fixed at 40mm. The tests were carried out in ambient temperature without any lubrication. The wear testing machine was microprocessor controlled where height loss and fric- tional force were monitored simultaneously. The height loss data was converted to volumetric loss by multiplying it with area of cross 0043-1648/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2008.12.011