Ring Rolling of IN 718 for Critical Engine Applications

Critical engine disks are typically die forged products due to the high demand on quality and reproducibility. Therefore, it is state of the art that the die forging process is well controlled by a closed loop controlled hydraulic press combined with a tight monitoring of process parameters, e.g. deformation velocity, press load, transfer time etc. Based on the geometry of the disk, for example, in the case of low pressure turbine disks that have a large inner diameter, die forging is not always the most cost efficient process. In these circumstances, ring rolling of a pre-shape for final die forging or direct ring rolling of the disk by using contoured rolls can result in a much higher material yield and reduced production cost and time. For critical components, that require a fine and homogeneous microstructure to fulfill the required mechanical properties, ring rolling has not been used due to the lack of process control and the difficulties to simulate the process. By using an improved process control of the ring rolling mill, in combination of an enhanced process monitoring, a suitable microstructure can be achieved during ring rolling. Results of rolled rings with rectangular and shaped contours made from IN 718 will be presented and the necessary process control and process monitoring will be described. In addition, microstructure results of rolled rings will be compared with simulation results.