Análise metalográfica e mecânica de válvulas convencionais e bimetálicas para aplicação em motocicletas

Abstract

Brazil is among the world's largest motorcycle markets, with a fleet exceeding 35 million units, intensifying competitiveness in the motorcycle parts sector and demanding components with high performance, durability, and competitive cost. In this scenario, intake and exhaust valves play a critical role in the internal combustion engine, as they operate under severe conditions of temperature, mechanical load, wear, and an aggressive chemical environment. Recently, a national company in the sector identified, in competing products, the adoption of a relevant technological innovation: the use of different materials for intake and exhaust valves and, specifically, the application of exhaust valves with bimetallic construction, combining different metal alloys in the stem and head. Given this innovation, this work aimed at the technical characterization of these competing valves, evaluating the materials, manufacturing processes, and metallurgical and surface quality of the components. To this end, metallographic tests, Vickers microhardness tests, and surface roughness tests were performed on intake valves, monolithic exhaust valves, and bimetallic exhaust valves. Microstructural analysis identified tempered martensitic microstructures in the stems, austenitic microstructures in the exhaust valve heads, and characteristic transition zones in the bimetallic construction. Hardness tests revealed the influence of surface treatments and coatings, as well as significant variations between different regions of the valves, while roughness tests allowed for the evaluation of surface finish in relation to functional requirements for wear resistance. The results indicate consistency between the adopted construction solutions and the operating conditions of the valves, demonstrating that the use of different materials and bimetallic construction constitutes a technically viable strategy for performance optimization. The study provides relevant support for both academic analysis and strategic decision-making in the industrial context of the motorcycle parts sector.