Investigation of 17-4PH steel microstructure and conditions of elevated temperature forming of turbine engine strut

In this paper, the warm forming process of a turbine engine strut made of 17-4PH (precipitation hardening) stainless steel is investigated. The blank is heated to a desired temperature using an industrial induction heater. The temperature value of the blank was measured using thermocouples and a pyrometer. The forming process at elevated temperatures is realized for a wide range of heating temperatures of 20-800 °C. The effect of overheating of the blank due to transfer of the blank from the heater to the stamping die using an industrial robot on the dimensional deviation of the drawpiece is considered. The geometry of the drawpieces was measured using an Atos 3D optical scanner (GOM, Germany). The smallest shape deviation of the drawpiece is obtained in the case of forming at 680 °C. To study the change of temperature during the heating and forming process, thermocouples and an optical pyrometer were used. The analysis of the microstructure of the blank material at different temperatures indicates that plastic strain in the temperature range of 20-800 °C causes an increase of banding of phase components of the microstructure. No evident effect of strain rate on the change of the 17-4PH steel microstructure is observed.