Solidification observations and sliding wear behavior of vacuum arc melting processed Ni–Al–TiC composites A.E. Karantzalis ⁎ , A. Lekatou, K. Tsirka Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece ARTICLE DATA ABSTRACT Article history: Received 14 January 2012 Received in revised form 18 April 2012 Accepted 24 April 2012 Monolithic Ni 3 Al and Ni–25 at.%Al intermetallic matrix TiC-reinforced composites were successfully produced by vacuum arc melting. TiC crystals were formed through a dissolution–reprecipitation mechanism and their final morphology is explained by means of a) Jackson's classical nucleation and growth phenomena and b) solidification rate considerations. The TiC presence altered the matrix microconstituents most likely due to specific melt–particle interactions and crystal plane epitaxial matching. TiC particles caused a significant decrease on the specific wear rate of the monolithic Ni 3 Al alloy and the possible wear mechanisms are approached by means of a) surface oxidation, b) crack/flaws formation, c) material detachment and d) debris–counter surfaces interactions. © 2012 Elsevier Inc. All rights reserved. Keywords: Ni–Al intermetallic matrix composites Vacuum arc melting Crystal growth Sliding wear performance 1. Introduction During the last two decades nickel–aluminum intermetallics, such as NiAl and Ni 3 Al, have attracted great research interest as potential candidate materials for structural and other applications, especially at high temperatures, due to their attractive properties such as high modulus of elasticity, relatively low density, high oxidation resistance and high melting point [1–4]. The systematic research efforts adopted during the last decades, revealed that problems such as ambient temperature, high brittleness and high temperature mechanical and wear performance instability can be effec- tively overcome by appropriate alloying and/or ceramic particle additions [1–7]. The Ni–Al system is, by metallurgical point of view, by far one of the most challenging systems and has attracted great scientific attention. Numerous phase transformations and microstructural features are involved depending on several parameters. Especially in the case of the two most important intermetallic phases – Ni 3 Al and NiAl – the prediction of the final microstructure can be proved to be a significantly difficult task. Crucial, nevertheless, research efforts such as those of Assadi et al. [8,9], Hunziker and Kurz [10], Li et al. [11] and Song et al. [12] have managed to enlighten the issue of microstructure constituents, taking into consideration key parameters such as, initial composition, solidification‐cooling rates, nucleation phenomena, growth kinetics considerations and alloying additions. TiC, due to its attractive properties such as low density, high temperature stability, high hardness, high modulus of elasticity etc., has been considered as one of the most promising reinforcing materials from intermetallic matrix composites [13–15]. Its beneficial contribution is most likely associated with the enhancement of the mechanical proper- ties and wear resistance at high temperatures. Chen and Wang [7,13,14,16–22] have extensively investi- gated the manufacture and properties of intermetallic–TiC composite materials for various different intermetallic matri- ces such as Fe–Al [13,14,16–18], Ti–Al [9–21] and Ni–Al [7,22], using laser cladding as the manufacturing technique. In their efforts, they observed that different intermetallic matrix systems, due to different elemental diffusion behaviors and MATERIALS CHARACTERIZATION 69 (2012) 97 – 107 ⁎ Corresponding author at: Department of Materials Science and Engineering, University of Ioannina, Greece. Tel.: + 30 2651009026. E-mail address: akarantz@cc.uoi.gr (AE. Karantzalis). 1044-5803/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.matchar.2012.04.013 Available online at www.sciencedirect.com www.elsevier.com/locate/matchar