Dry sliding wear system response of ferritic and tempered martensitic ductile iron

Abstract

Abstract. Spheroidal graphite cast iron (SG iron) is the most preferable member of cast iron family due to its strength and toughness along with good tribological properties. SG iron specimens with annealed and martensitic matrix were subjected to dry sliding wear condition and the system response was correlated to matrix microstructure. Respective microstructure was obtained by annealing and quench and tempering heat treatment process for an austenitizing temperature of 1000°C. Specimens were subjected to Ball on plate wear tester under 40N, 50N, 60N load for a sliding distance of 7.54m. Except for quench and tempered specimen at 50N, weight loss was observed in every condition. The wear surface under optical microscope reveals adhesive mechanism for as-cast and annealed specimen whereas delaminated wear track feature was observed for quench and tempered specimen. Keywords: SG cast iron, dry sliding wear, microstructure, wear morphology I. IntroductionSpheroidal graphite cast iron (SG iron) or ductile iron (DI) unlike every other cast iron has graphite in the form of spheroids which act as crack arrester, due to which it possesses higher strength and toughness along with better wear resistance. Furthermore it has been proved that the properties of SG iron can be improved by application of suitable heat treatment process leading to transformation of ascast ferritic or ferritic/pearlitic matrix into pearlitic, martensitic and bainitic. Austempered ductile iron is one of the most favorable materials among all other type because of its excellent strength, toughness, wear resistance, fatigue strength and fracture toughness [1][2][3][4][5][6][7][8]. Tribological investigation carried out on austempered SG iron with varying austempering time and temperature, reported increased wear resistance with increasing austempering temperature and time along with increased hardness during wear due to the bainitic ferrite which is less prone to thermal instability than martensite, might undergo strain hardening [9,10]. Tempering treatment on ductile iron with boron increased the wear resistance but with increasing boriding time wear rate of boro-tempered ductile iron decreased [11]. Apart from alloying element and heat treatment graphite nodule size and distribution affects the wear resistance of SG iron. According to a study by Sugishita and Fujiyoshi [12] and Zimba et.al [13] presence of large size graphite nodules reduces the wear rate by acting as lubricating agent.

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

“…Conversely the aspect ratio of graphite nodules result in less graphite at the surface, consequently an incomplete graphite film forms offering less protection [26]. However the nodules do not act as stress raisers during a contact overload [23], [27]. The present study is concerned with determining the influence that graphite morphology has on the scuffing behaviour of an EN-GJS 400-15 spheroidal cast iron, compared to a flake cast iron structure [17] in a simulated piston ring and cylinder liner contact.…”