Mechanical and fatigue response of high-alloyed carbon spring steels: Impact of different heat treatments

60MnSiCr4 and 52SiCrNi5 are two high-strength steels whose applications involve many different industrial sectors. They can be used for bolts and springs and have wide applications in the field of automatic machines and machine tools for gripping devices and collet fabrication, as they take advantage of their strength, toughness and machinability. Nevertheless, literature scientific data are currently lacking, which was the main motivation for this thorough study aimed at a detailed characterisation of the mechanical response of these materials. Both static and fatigue properties have been experimentally investigated, complying with the recommendations of the related International Standards, with the aim of comparing the performance for different hardness values for each material. Moreover, the impact of heat treatment on geometry deformation was also studied, to compare the repeatability of the process and related outcomes between the two observed steels. The following statistical processing of the experimental campaign data led to determining the main material mechanical properties: yield point, ultimate tensile strength, elongation and Young’s modulus regarding static parameters. A careful fatigue experimental campaign led to the determination of S-N curves and fatigue limits, thus enabling lifespan prediction and comparisons among the expected strengths. In addition, fractography analyses were conducted to assess the behaviour of crack propagations for the studied materials and conditions. Finally, Vickers tests by a microdurometer were performed to validate the uniform distribution of hardness values along the thickness.