Problems associated with the use of cast iron components in automotive friction braking/clutch systems, namely corrosion, uneven wear, distortion and in the worst cases structural failure have been overcome using thermally conducting coatings. The thermally sprayed coatings are composites of ceramic particles dispersed in a metal matrix. The coatings have good thermal conductivity, excellent corrosion and wear resistance with high energy absorption and heat dissipation. Careful selection of the friction material allows adequate friction levels to be generated over a wide range of operating temperature with the minimum levels of friction couple wear and disc cracking.

SEM, RBS, EDX and EDX mapping were used to characterise rubber and silicon surface modified by means of self-ion assisted deposition (SIAD). It was found that SIAD of Cr, Zr and W are accompanied by incorporating of C, O, Al and Si into a coating, what can promote a creation of observed grainless layers. Modified rubber surfaces have quasi-periodical topography which may be due to build in stress as a result of self-ion bombardment. Evolution of RBS signals from metal and incorporated elements are associated with an intermixing effects in the layer/substrate region.

The chemical nature of the transfer film (TF) or third body layer (TBL) formed at the friction interface during automotive friction braking has been studied in detail using energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopic (XPS) analytical techniques. Optical and scanning electron optical methods have been used to examine the friction surfaces of the two elements of the friction couple, grey cast iron and asbestos free friction materials. Evidence is presented which relates the friction characteristics of the couple to transfer film chemistry and friction material composition. The role of lubricants and abrasive additions to the friction material and their effectiveness at a range of contact pressures/temperatures, is examined in detail. Information obtained from imaging X-ray photo-electron spectroscopy studies will be used to show that transfer film chemistry is dependent upon asperity temperature/contact pressure and the composition of the friction couple components. These data are used to explain changes in friction coefficient which may occur during automotive braking. The influence of transfer film chemistry upon wear rate of the friction couple components is also discussed. Friction performance was found to be independent of transfer film thickness or topography but sensitive to transfer film composition. The chemistry of the transferred layer was influenced by the morphology and mechanical properties of the friction material abrasive. Friction material wear rates and friction coefficient were not interrelated.

X-ray photo electron spectroscopy (XPS) has been used to determine the nature of the ''TRANSFER FILM'' (TF) or ''THIRD BODY LAYER'' (TBL) formed at the friction interface of some simple friction couples using materials commonly employed in automotive braking systems. Imaging X-ray photo electron spectroscopy (IXPS) has been used with good effect to illustrate both the interaction and relative distribution of the various chemical species present on the grey cast iron surface after rubbing against a number of different asbestos free friction materials.Evidence is presented which highlights the rela. tionship between transfer film chemistry, friction material composition and work done during braking. The role of lubricant additions to the friction material, in particular their effectiveness at a range of asperity temperatures, is examined in detail. The influence of chemical changes at the interface is also discussed.The results obtained in this study allows conclusions to be drawn about the dependence of transfer film chemistry on the asperity temperature and the composition of the friction material. This information is used to explain some or the differences in friction performance which may occur during automotive braking.

During automotive braking a friction heat affected layer is introduced onto the surface of the two components of the friction couple together with the transfer of material between rubbing faces to form a transfer film (TF) or third body layer (TBL).In this investigation energy dispersive X-ray analysis (EDX) and X-ray photo electron spectroscopy (XPS) have been used to study the chemistry of transfer films formed on the grey cast iron The results show a clear connection between transfer film chemistry, asperity temperature and the composition of the friction material, especially lubricant additions. Evidence is presented which relates the friction characteristics of the couple to transfer film chemistry.