Ž . Wear 242 2000 18–27 www.elsevier.comrlocaterwear Friction and wear behavior of Ti following laser surface alloying with Si, Al and Si q Al J. Dutta Majumdar a , B.L. Mordike b , I. Manna a, ) a Metallurgical and Materials Engineering Department, Indian Institute of Technology, Kharagpur 721302, India b Institut fur Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6, D-38678 Clausthal–Zellerfeld, Germany ¨ ¨ Received 19 May 1999; received in revised form 29 February 2000; accepted 29 February 2000 Abstract Ž . This study concerns the friction and wear behavior of Ti following laser surface alloying LSA with Si, Al or Si qAl. The said tribological characteristics of the laser-alloyed samples, subjected to the earlier determined optimum conditions of LSA, were investigated in terms of the variation of wear depth as a function of load and time using a computer-controlled reciprocating ball-on-disc wear testing machine fitted with an oscillating hardened steel ball. A detailed post wear microstructural analysis was conducted to determine the mechanism of wear and role of alloying elements in improving the resistance to wear. It appears that LSA with Si is more effective in improving the wear resistance of Ti than that by Si qAl or Al alone. The enhanced wear resistance in Si surface alloyed samples has Ž . been attributed to the presence of uniformly distributed Ti Si in the alloyed zone AZ . q 2000 Elsevier Science S.A. All rights 5 3 reserved. Keywords: Laser surface alloying; Wear resistance; Friction; Titanium; Silicon; Aluminum 1. Introduction Ti and its alloys are extensively used in jet engine compressor components, high-pressure heat exchangers, sea water desalination plants, offshore structures and petro- chemical plants owing to their high specific mechanical wx strength and corrosion resistance 1 . However, the wear resistance of TirTi alloys is inadequate in many of these applications. It is known that the microstructural changes obtained by heat-treating Ti alloys may impart marginal wx improvement in the sliding wear resistance 2 . Miller and wx Holladay 3 have reported that wear resistance could be partially improved through surface modification provided the adhesion of the coating to the substrate is strong. In wx this regard, Beck and Danovich 4 have experimentally examined the usefulness of stronger coating–substrate bonding in the case of diffusion bonded electroless Ni coating on Ti alloys. Similar strong coating–substrate bonding is possible in the glow discharge ion-nitriding ) Corresponding author. Tel.: q 91-3222-83266; fax: q 91-3222-55303. Ž . E-mail address: imanna@metal.iitkgp.ernet.in I. Manna . w x process 5,6 . Though such nitrided layer is characterized by high hardness, the thickness of the said layer is usually Ž . very low 2–3 mm. In the recent past, several attempts have been made to improve the wear resistance of Ti alloys by laser surface Ž . w x alloying LSA 7–10 . LSA involves rapid melting, inter- mixing and solidification of the pre- or co-deposited alloy- ing elements with a part of the underlying substrate to Ž . form an alloyed zone AZ confined only to the near-surface w x region within a very short interaction time 11–13 . The process is characterized by an extremely high heatingr Ž 4 10 . Ž 5 cooling rate 10 to 10 Krs , thermal gradient 10 to 8 . Ž 10 Krm and solidification velocity maximum of up to . w x 30 mrs 12 . As a consequence, LSA may extend the solid solubility limit, and result in a metastable and novel w x microstructure. Mordike 14 has suggested that laser as- sisted gas nitriding could significantly enhance the hard- w x ness in pure Ti or Ti–6Al–4V. Ayers 15 has attempted a similar improvement by injecting carbide particles during laser surface melting of TirAl-alloys. Subsequently, w x Yarramarreddy and Bahadur 16 have studied the tribolog- ical behavior of Ti–6Al–4V subjected to laser surface melting and LSA. 0043-1648r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. Ž . PII: S0043-1648 00 00363-X