Scuffing mechanisms of EN-GJS 400-15 spheroidal graphite cast iron against a 52100 bearing steel in a PAO lubricated reciprocating contact

Abstract

Scuffing of the automotive piston ring on liner contact is likely to increase due to engine downsizing and the use of low viscosity engine oils to achieve greater fuel efficiency. This work investigated the scuffing mechanism of EN-GJS 400-15 spheroidal graphite cast iron caused by reciprocating sliding of a 52100 roller bearing element lubricated with PAO base oil.The contact was conditioned at 100N and 15 Hz over a stroke of 25 mm at 180 o C. Subsequently the load was incremented in 100 N/min steps at 5 minute intervals until severe scuffing occurred, indicated by a rapid rise in the average friction coefficient. High speed friction was used to determine the onset of mild and severe scuffing. Stylus and 3D optical profilometery revealed that mild scuffing produced a smooth surface with small cracks compared to the severe scuffed surface which contained adhesive wear craters of 40 µm in depth. Focused ion beam cross-sections of the mild scuffed surface and EDS analysis of the microstructure indicated that cracks were initiated by dross inclusions with a similar morphology to flake graphite. The transition to severe scuffing occurred at 700N when crack networks facilitated adhesive transfer of cast iron material to the counter-surface.

Early wear detection and its significance for condition monitoring

“…One of the main influences of surface wear is surface roughness: The mass loss of mild wear can be associated with global asperity height [12][13][14]. However, the evolution of surface roughness is the result of a combination of various wear mechanisms, including micro-pitting formed from surface material removal and plastic deformation [9,15]; surface oxidation due to high load [16], sliding speed [17] and relative humidity [18][19][20][21]; adhesive wear due to absence of oxidation film [22] and higher energy asperity contact [23]; abrasive wear caused by large [24] and a high concentration of particles [25].…”

Experimental Analysis of the Influence of the Application of TiN, TiAlN, CrN and DLC1 Coatings on the Friction Losses in an Aviation Internal Combustion Engine Intended for the Propulsion of Ultralight Aircraft

“…Currently, in order to limit the effects of these undesirable phenomena, many manufacturers are working on the development of synthetic engine oils and oil additives that reduce the friction and vibration of piston rings [10][11][12][13]. Reducing the dynamic viscosity of the oil reduces the internal friction resistance in the oil film, as does the use of many different oil additives reducing the friction in direct contact with micro-inequalities [14][15][16][17]. There are many different techniques that are used to reduce engine drag torque, especially when texturing the cylinder-bearing surface [18][19][20].…”

Effects of Cast-Iron Surface Texturing on the Anti-Scuffing Performance under Starved Lubrication

“…Cylinder scuffing is generally considered to be an abrupt rise in the friction coefficient, accompanied by apparent damage on the cylinder liner surface [3,4,5,6]. Many efforts were made to investigate the scuffing phenomenon to prevent such failure [7,8,9,10,11,12]. Coating on the piston ring proved to be an effective method, which may provide advantages such as friction reduction and improved wear and scuffing resistance.…”