Acta Materialia 50 (2002) 4913–4924 www.actamat-journals.com Ti–6Al–4V strengthened by laser melt injection of WC p particles J.A. Vreeling, V. Ocelı ´k, J.T.M. De Hosson * Department of Applied Physics, Materials Science Center and the Netherlands Institute for Metals Research, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands Received 11 August 2002; received in revised form 19 August 2002; accepted 19 August 2002 Abstract The laser melt injection (LMI) process has been explored to create a metal–matrix composite consisting of 80 μm sized WC particles embedded in a Ti–6Al–4V alloy. In particular the influences of the processing parameters, e.g. power density, scanning speed and powder flow rate, on the dimensions and microstructure of the laser track have been examined. The microstructure was investigated by advanced transmission electron microscopy including energy filtering techniques and scanning electron microscopy with an integrated electron back-scatter diffraction/orientation imaging microscopy. Typical dimensions of a single laser track are a width of 1.8 mm and a depth of 0.7 mm. The volume fraction of the WC particles is about 0.25–0.30. An important finding is that the particle distribution is homo- geneous and that the particles are injected over the whole depth and whole width of the melt pool. Only occasionally a crystal orientation relation between WC, W 2 C and TiC is observed. A substantial increase in wear resistance was observed, i.e. 0.5 × 10 -6 mm 3 /Nm for the WC p laser embedded and 269 × 10 -6 mm 3 / Nm for the untreated Ti–6Al–4V alloy at the same contact stress (20 MPa).  2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. Keywords: Laser treatment; Scanning electron microscopy; Transmission electron microscopy; Electron back-scatter diffraction; Titanium; Carbides; Microstructure; Wear 1. Introduction Although titanium alloys exhibit excellent material properties like a high strength to weight ratio, good corrosion resistance, good creep, fatigue and toughness properties [1], the high fric- tion and poor wear resistance hamper many poten- * Corresponding author. Tel.: +31-503634898; fax: +31- 503634881. E-mail address: hossonj@phys.rug.nl (J.T.M. De Hosson). 1359-6454/02/$22.00.  2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved. PII:S1359-6454(02)00366-X tial applications. Protecting Ti with a coating is an adequate solution to improve these properties, while keeping the advantageous bulk properties unaffected. In this work a high power laser is used to protect Ti–6Al–4V by means of the so-called laser melt injection (LMI) process [2–5]. In this process the laser beam is used to locally melt the top layer of a metal (Ti–6Al–4V) substrate, while simultaneously a ceramic powder (80 μm sized WC particles) is injected into the melt pool. During rapid solidification of the substrate the particles are trapped and a metal–matrix composite (MMC) layer is formed, while the bulk is unimpaired.