Comprehensive Study on Thermal Fatigue and Microstructural Degradation of Clutch Pressure Plates in Commercial Vehicles

This paper presents a detailed failure analysis of an automotive clutch pressure plate subjected to severe thermal loading conditions during operation. The study investigates the material’s chemical composition, microstructural evolution, and mechanical property changes resulting from thermal exposure. The base metal was identified as grey cast iron conforming to FG 260 standards, ensuring a baseline for understanding its expected behavior. The investigation reveals significant microstructural transformations, including the formation of martensite, tempered martensite, and bainite, which arise due to the cyclic heating and cooling typical of clutch service. These phase changes adversely affect the mechanical integrity of the pressure plate, contributing to crack initiation and propagation. The failure was isolated to the pressure plate, with related clutch components remaining unaffected, highlighting the localized impact of thermal stresses. The findings emphasize the critical interaction between material composition, thermal history, and microstructure in determining component longevity. The study provides valuable insights to guide future improvements in material selection, heat treatment processes, and operational practices to enhance the durability of friction materials in automotive applications. Keywords: Thermal Fatigue, Microstructural, Clutch Pressure Plates, Commercial vehicles, failure analysis, mechanical property, FG 260 standards, powertrain, Diaphragm Spring, Clutch Cover, IS 6331 standards, Clutch, Pressure plates, Microstructure, Martensite, Grey cast iron, Thermal load, Thermal cracks, Heat discolouration