Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser L.A. Dobrzan ´ski a , M. Bonek a, * , E. Hajduczek a , A. Klimpel b a Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A, Poland b Welding Department, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A, Poland Available online 2 March 2005 Abstract The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented. # 2005 Elsevier B.V. All rights reserved. Keywords: Hot-work tool steel; Surface layer; Alloying; Laser HPDL 1. Introduction Improvement of the surface properties of materials used to date constitutes one of the goals set to the research institutions active in the materials engineering area. Possibilities of increasing the functional proper- ties of the hot-work alloy tool steels by modification of their chemical composition in a conventional way are very limited already. Laser technique represents the especially promising tool for solving the contemporary surface engineering problems thanks to the physical properties of the laser beam, making it possible to focus precisely the delivered energy in the form of heat on the surface layer. Moreover, methods, which are not based on partial melting of the surface alone, but on partial melting with the simultaneous introduction of the alloying elements with high hardness, like carbides, are being employed more and more widely for modification of the surface layer. High-cooling rates are obtained in this process and its end result is the fine-grained material with the super-cooled phases. Material transport in the liquid metal, caused by the surface tension forces, features the main factor deciding the development of the alloyed layers. The non-uniform material heating resulting from the laser beam impact causes development of a big surface tension gradient on the surface of the liquid. The force is directed outside from the beam centre, where is the highest temperature value to its edge and causes movement of the molten material [1–5]. www.elsevier.com/locate/apsusc Applied Surface Science 247 (2005) 328–332 * Corresponding author. Tel.: +48 32 2372910; fax: +48 32 2372281. E-mail address: mb@zmn.mt.polsl.gliwice.pl (M. Bonek). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.01.126