Fatigue behavior of rolled and forged tungsten at 25°, 280°and 480°C

Pure tungsten has been chosen as the target material at the European Spallation Source facility in Lund. Calculations show that the target temperature can reach 500°C momentarily during the spallation process, leading to thermal fatigue. Target life estimations require fatigue data at different temperatures and this work focuses on generating such data for pure, unirradiated, rolled and forged tungsten in the range 25°-480°C. For specimens oriented in the rolling direction, tensile tests at room temperature indicated Young's modulus values in the range 320-390 GPa, low levels of plasticity (<0.23%) and UTS values in the range 397 MPa (unpolished) and 705 MPa (Polished). UTS for forged specimens were around 500 MPa. Stress-controlled fatigue tests were conducted in the tensile regime, with a runout limit of 2 × 10⁶ cycles. At 25°C, unpolished specimens had fatigue limits of 150 MPa (rolling and transverse direction), and 175 MPa (forged). For polished specimens in the rolling direction, fatigue limits were higher at 237.5 MPa (25°C) and 252.5 MPa (280°C). The forged specimens showed slightly better fatigue properties and marginal cyclic hardening at 480°C.