IMPROVEMENT OF FATIGUE PROPERTIES OF 34CRNIMO6 STEEL BY CONTROLLED THERMOMECHANICAL TREATMENT

Providing materials with optimized properties for certain application is more and more demanded nowadays. In order to fulfil this requirement a wide range of materials in broad range of thermal or thermomechanical states have to be investigated. To keep costs for such a materials development at acceptable manner a physical thermomechanical simulators are efficiently applied. A thermomechanical simulator is applied for themomechanical process development providing improved fatigue life of the steel investigated in this paper. The investigated 34CrNiMo6 steel is traditionally used for highly loaded components with very high hardenability, fatigue strength and toughness. There is no demand for change of the material, but for utilization of the full material potential. In the current study several thermomechanical procedures and conventional heat treatment are applied to the material. The heating rate and temperature of deformation process is kept the same as well as proven deformation process providing required fine grained microstructure. The variables are cooling rate from the forming temperature and annealing temperatures. Properties of conventionally heat treated material and thermomechanically treated material in the simulator are compared here. Samples with various microstructures are tested and the materials mechanical properties are evaluated and the best candidates are chosen for closer investigation. In this way thermomechanical procedure providing material with extended service life of 34CrNiMo steel is established.