Wear 270 (2011) 247–251 Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear Interference measurements of deposits on cylinder liner surfaces Zlate Dimkovski a,∗ , Lars Bååth a , Stefan Rosén b , Robert Ohlsson c , Bengt-Göran Rosén a a Functional Surfaces Research Group, School of Business and Engineering, Halmstad University, P.O. Box 823, SE-301 18 Halmstad, Sweden b Toponova AB, Halmstad, Sweden c Volvo Power Train Corp., Volvo Group, Göteborg, Sweden article info Article history: Received 21 April 2010 Received in revised form 26 October 2010 Accepted 28 October 2010 Available online 4 November 2010 Keywords: Cylinder liner deposits Surface characterisation Run-in Engine tests abstract The accumulation of deposits in the honing grooves of the cylinder liner surfaces of internal combus- tion engines is undesirable as they seal the grooves (reducing their oil retention capability) and increase engine’s oil consumption. As part of a long-term programme of truck engine development, after different running times and under similar conditions of load, engine speed and lubrication, a number of grey iron cylinder liners were axially sectioned, measured, inspected and a presence of deposits was discovered. These deposits were characterised in order to gain knowledge about their origin and quantities. The X-ray energy dispersive analysis revealed elements stemming from the oil/fuel (C, O and S), from the detergent (Ca and Mg), from the anti-wear additive (Zn and P), and from some contaminants (K and Si). Higher concentration of S and Ca were mostly found in the honing grooves covered with deposits suggesting a domination of the detergent additive. Deposit thickness measurements obtained by a white light interfer- ometer revealed patchy deposit topographies concentrated at the top region reducing towards the bottom of the liner which was also confirmed by scanning electron microscope measurements. Despite the lim- itations of the interferometer, it has been shown that the interference measurements are sufficiently reliable for a quick and objective quantification of the overall deposit accumulation. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In order to comply with increasingly stringent emission reg- ulations, the developers of internal combustion engines strive to reduce the oil consumption, which is not only of environmental interest but also of saving of resources. One of the factors adversely affecting the oil consumption is the accumulation of deposits in the piston–cylinder assembly. Cylinder liners are machined by plateau honing process leaving a surface topography with smoother plateaus and deep valleys for oil and debris retention. Coverage of the deep valleys by deposits would smooth the running surface, reducing the oil storing capability and impairing the lubrication. As a consequence, the oil consumption increases and extra overhauls are required. This problem is frequently reported in marine engines and has been well documented [1,2]. Deposits have been studied in the natural gas engines, where a glazing deposit of Fe 3 O 4 and car- bon was found on the liner surfaces after run-in experiments [3] and in biogas engines, where silicon-containing compounds from landfill gas and ash-forming lubricant additives contributed to hard deposits to be formed on the liners [4]. Regarding the heavy duty diesel (HDD) engines, relevant studies on piston’s oil and deposits ∗ Corresponding author. Tel.: +46 35167752; fax: +46 35167564. E-mail address: Zlate.Dimkovski@hh.se (Z. Dimkovski). have been conducted. The top land piston deposits are composed of organic and inorganic materials: organic soot and oxidised oil as resin and inorganic metals and salts (ash) [5]. The inorganic salts are derived from the ZDDP and metallic detergents. Cal- cium sulphate (CaSO 4 or in form of CaSO 4 ·1/2H 2 O-plaster of Paris) and/or MgSO 4 ·6H 2 O are the main inorganic materials depending on whether Ca and/or Mg based detergent has been used. These minerals are distinctive crystalline compounds formed during the neutralisation of the combustion acid (H 2 SO 4 ) by the detergent (CaCO 3 ) to form a neutral salt (CaSO 4 ). The oil samples taken in situ from the piston’s top ring groove of a HDD engine revealed com- pounds of anti-wear ZDDP (Zn and P) additive and detergent (Ca and Mg) with higher concentrations of the latter [6]. A little is known about the cylinder liner deposits of HDD engines and there is no scientific work published to the best knowledge of the authors. The accumulation (i.e. formation and removal) of deposits on the cylinder liners is a complex process. In the marine sector it is generally agreed that it is dependent on interactions among the fuel composition, lubricant formulation and engine design and loading. To this, Buhaug [1] has added that the problem originate when the balance between the oil film load (temperature and con- tamination) and renewal (global/local oil film renewal, lubricant resilience and dispersing power) is upset. Because of the inac- cessibility and large number of variables involved in this process, it is difficult to determine the exact cause. Other difficulties are 0043-1648/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2010.10.066