Effect of different Mechanical Processes for Surface Treatment on Properties of the Titanium Alloy Ti6246Friday (10.11.2017) 11:15 - 11:35 Part of:
Titanium alloys are used in aircraft engines mostly in compressors at lower temperatures up to 500 °C. The main reason for its use is the opportune ratio between weight and strength. The titanium alloy Ti6Al-2Sn-4Zr-6Mo has a specific strength which is approximately 8.5 % higher compared to the commonly used titanium alloys Ti6Al-4V and Ti6Al-2Sn-4Zr-2Mo at a temperature of 450 °C. This property leads to a lower part weight due to a possible reduction of wall thickness in the lay out design. The alloy Ti6246, which has been investigated in the present work, was formed in the ß-area, high temperature annealed in the (@+ß)-area and succeedingly treated with a standard hardening process. The microstructure consists of lengthy formed ß-grains with precipitations of primary, coarse @-plates and secondary, fine @-plates. The present work investigates the influence of deep rolling, ultrasonic shot peening, rotary flapper peening and a new pneumatic needle peening process in comparison to conventional shot peening with steel shot on the mechanical properties of Ti6246. For the shot peening processes different intensities were being used. With the deep rolling procedure the parameters rolling ball diameter, hydro-static pressure, rolling speed as well as the overlap of adjacent rolled lines were varied. For residual stress, micro hardness measurements and for characterising the surface topography flat specimens were used. The determination of the fatigue life was carried out using rotating bending tests at 450 °C in a regular atmosphere. For the rotary flap peening process, the pneumatic needle peening process in comparision with the conventional shot peening process the determination of the fatigue life was carried out using cyclic bending tests in a regular atmosphere.