Wear 270 (2011) 850–856 Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear Application of hard coatings for blanking and piercing tools B. Podgornik a,∗ , B. Zajec b , N. Bay c , J. Viˇ zintin a a University of Ljubljana, Centre for Tribology and Technical Diagnostics, Bogiˇ siˇ ceva 8, SI-1000 Ljubljana, Slovenia b HIDRIA Rotomatika d.o.o., Spodnja Kanomlja 23, SI-5281 Spodnja Idrija, Slovenia c Technical University of Denmark, Department of Mechanical Engineering, Produktionstorvet 425, 2800 Kgs. Lyngby, Denmark article info Article history: Received 23 September 2010 Received in revised form 15 February 2011 Accepted 16 February 2011 Available online 23 February 2011 Keywords: Blanking Piercing PVD coatings Friction Wear abstract The aim of the present investigation was to examine the possibility of reducing lubrication and replacing expensive tungsten carbide material in blanking/piercing through introduction of hard tool coatings. Results show that hard PVD coatings can be successfully used in blanking/piercing applications, even on softer tool steels, thus leading to reduced friction and wear as well as to lower costs of the tool. However, preparation of the substrate material and good coating to substrate adhesion are crucial. On the other hand, even with the use of low friction coating (DLC) stamping force exceeds critical value under dry friction conditions and leads to tool failure. Therefore, at present oxidation and temperature resistant hard coatings can give improved wear resistance of stamping tools, but elimination of lubricants in blanking and piercing processes is still not feasible. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Blanking and piercing operations are widely used for mass pro- duction of precision engineering components. The quantity and quality of the stamped components, assessed by the profile of the formed surface and the deviation from the nominal dimensions of the blank and stock, depends on many factors such as tool design, tool material properties, stamping conditions and especially tool wear [1]. In punching and blanking operations, especially the punch is exposed to high dynamic loads, to sliding motion against work material and high contact temperatures [2], which lead to high fric- tion and wear of the tool [3]. The severe tribological conditions between the punch stem and the exposed, virgin work-piece mate- rial causes pick-up of work-piece material on the tool and increase in stamping force as well as extraction force [4–6], while tool wear directly affects the part formability and surface quality, and causes production loss, cost increase and delays [7]. In order to reduce friction and wear of the punch different lubricants such as environ- mentally hazardous chlorinated paraffin oils and/or tool materials made from tungsten carbide are used. Use of tungsten carbide implies high tool costs, while lubricants are not preferred due to environmental issues and subsequent cleaning requirements. Reduction of lubricating oil in machining and forming becomes a critical issue to improve the environmental friendliness in practical operations [8–10]. In particular, once lubricants are used in stamp- ∗ Corresponding author. Tel.: +386 1 4771 463; fax: +386 1 4771 469. E-mail address: bojan.podgornik@ctd.uni-lj.si (B. Podgornik). ing complete removal of oils is difficult or nearly impossible even by using cleansing agents. Recycling of cleansing agents as well as disposal of waste also becomes an issue for safety and protection against pollution [11]. In order to reduce/eliminate the need for lubrication and to introduce less expensive tool materials surface engineering tech- niques providing low friction and wear resistant surface are required. One way of modifying the surface, already effectively used in the forming industry, is thermo-chemical surface treat- ment of the tool [12,13]. In the last decades hard PVD and CVD coatings have started to successfully compete with the traditional thermo-chemical treatments, especially in terms of abrasive wear resistance [14]. However, although hard and corrosion-resistant coatings show high hardness and are frequently used to protect and enhance the lifetime of cutting tools, the majority of form- ing tools is still uncoated [15]. Beside a complex shape that often makes the forming tool difficult to coat, the traditional hard coat- ings such as TiN, TiC and CrN cannot meet blanking or piercing tool requirements, including good adhesion to the base material to withstand high loads and shearing forces without chipping or peeling, high toughness and low friction against stamped material [1,16,17]. However, in the last couple of years, tremendous progress has been seen in the field of coating deposition and design, lead- ing to greatly improved tribological properties of contact surfaces [18,19]. Especially carbon-based and multicomponent and multi- layered coatings are the promising candidates to put the concept of “cheap” and reliable coated tools for dry or near-dry stamping into practice [20]. Therefore, the aim of this investigation was to examine the pos- sibility of eliminating/reducing lubrication and replacing expensive 0043-1648/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2011.02.013