Materials Science and Engineering A 418 (2006) 357–363 Tribological wear behavior of diamond reinforced composite coating K. Venkateswarlu a,∗ , Ajoy Kumar Ray a , Manoj Kumar Gunjan a , D.P. Mondal b , L.C. Pathak a a National Metallurgical Laboratory, Jamshedpur 831007, India b Regional Research Laboratory, Bhopal 462026, MP, India Received in revised form 7 December 2005; accepted 7 December 2005 Abstract In the present study, diamond reinforced composite (DRC) coating has been applied on mild steel substrate using thermal spray coating technique. The composite powder consists of diamond, tungsten carbide, and bronze, which was mixed in a ball mill prior deposition by thermal spray. The microstructure and the distribution of diamond and tungsten carbide particle in the bronze matrix were studied. The DRC-coated mild steel substrates were assessed in terms of their high stress abrasive wear and compared with that of uncoated mild steel substrates. It was observed that when sliding against steel, the DRC-coated sample initially gains weight, but then loses the transferred counter surface material. In case of abrasive wear, the wear rate was greatly reduced due to the coating; wherein the wear rate decreased with increase in diamond content. © 2005 Elsevier B.V. All rights reserved. Keywords: Diamond reinforced composite; Coatings; Wear rates; Abrasion; Sliding 1. Introduction Over the past few decades, the need for efficient machining and polishing of industrial components had led to the devel- opment of superhard materials. Diamond being the hardest amongst all the superhard materials was extensively used. In many applications, large numbers of diamond-based compo- nents are required and diamond powders are used in diamond- reinforced composites (DRC). It may be noted that DRC coating is different from the diamond film or diamond-like carbon coat- ing, which are produced by vacuum deposition techniques. The optimal substrate temperature for pure diamond coating is about 900 ◦ C, which severely limits the range of substrates for prac- tical uses. Furthermore, it is difficult to sinter diamond powder to make monolithic diamond. Therefore, to exploit the hardness of diamond for various industrial applications, diamonds must be bonded with other materials. In view of this, diamond based composites (bonded with metal and polymer) are developed and widely used in industries. In many of those engineering appli- cations, the diamond-based composites are used in the form of coatings [1–5]. Though a large number of techniques are available for the fabrication of composite coatings, thermal and plasma spray coatings are industrially popular. Thermal spray ∗ Corresponding author. Tel.: +91 657 2721709; fax: +91 657 2270527. E-mail address: karodi2002@yahoo.co.in (K. Venkateswarlu). technique being a low cost process can easily be adopted in industries [4]. The diamond-based composite coating on any substrate is expected to exhibit the following advantages: excel- lent wear and corrosion resistance (depending on the matrix). Several properties of the composites such as electrical resis- tivity, abradability or abrasive characteristics, surface textur- ing, catalytic and prosthetic applicability can be tailored. The diamond-reinforced composites are used in diamond polishing wheels, diamond wafer blades, metal scooping tools, etc. [1–4]. The application of this coating material is mainly dependent on the requirements. The diamond based coating in general is sub- jected to abrasion and sliding wear during various operations [5]. Though a significant amount of work has been done on the development of diamond-based composites [6–8], their tribo- logical behavior has not been studied adequately. In this paper, the tribological behavior of diamond reinforced composite coat- ing fabricated by a thermal spray technique is discussed in terms of sliding and high-stress abrasive wear. 2. Experimental 2.1. DRC coating Mixed metal powder comprising diamond (C), tungsten car- bide (WC) and bronze (B) powder were selected as starting materials and thoroughly mixed in a ball mill. The composi- 0921-5093/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2005.12.004