Research On Hot Deformation Behavior And Crack Propagation Of Turbine Blade Steel

During the steam turbine generation equipment, blades are the core components, which work under severe operating conditions, such as elevated temperature, high load, complicated stress, etc. Coupled with the effects of poor process parameters, these parameters can easily lead to the emergence of forming defects. The defects would hinder the smooth running of blades, and even the safety of steam turbine and power plant. With the increasing capacity of steam turbine, the load on the blade is even higher, which requires for higher processing quality of blades. 2Cr11Mo1 VNbN martensitic stainless steel is the main material for the production of steam turbine blade. However, studies about this steel are mainly concentrated on the process of smelting and heat treatment, seldom studies are about the forging process parameters. The actual production process of blades is based on production experience, and the cost is high. Thus, it is necessary to determine the forming process parameters of the material. The main work of this research is as follows:In this study, 2Cr11Mo1 VNbN steel was tested by hot compression to obtain the rheological data of the steel and the influence of temperature and strain rate on the steel was investigated. Based on Johnson Cook model and Arrhenius equation, corrected models that consider the compensation of deformation temperature and strain were established. By comparing the predicted values with experimental results, it is found that the modified models can describe the flow behaviour with high accuracy.Based on the rheology and the obtained data of the steel, the thermal processing characteristics maps of the steel were established. The processing power dissipation rate and flow instability region were analysed, and the best technological parameter range was determined, combined with the optical microscopy. The maps can act as a reference for the actual process of the steel.The analysis of I type crack and the calculation of stress intensity factor of the steel were studied by extended finite element and fracture mechanics with ABAQUS software.Rheological behaviour, hot working characteristics and crack propagation were studied through experiment and numerical simulation method. This study can provide a practices basis for optimization of process parameters to attain high quality products.Material testing and theoretical analysis method were launched to study elevated temperature forming and crack propagation of 2Cr11Mo1 VNbN blade steel. Research results can provide a reference to improve the product quality and prevent the appearance of fracture.