The High-Temperature Mechanical Properties of EN 1.4509 Stainless Steel Cast Using Investment Casting

The high-temperature (600-900 °C) mechanical properties of EN 1.4509 stainless steel made by investment casting were studied by changing the Nb content based on this stainless steel composition standard. The results indicate that with an increase in tensile temperature, the high-temperature strength shows a downward trend and the high-temperature plasticity increases. The results also indicate that with an increase in Nb content, the high-temperature strength rises continually and the high-temperature plasticity decreases; for example, the tensile strengths at 900 °C of Steel A, Steel B and Steel C are 21, 25 and 31 MPa, respectively, and the yield strengths are 15, 20 and 22 MPa, respectively, and the elongations are 97.7, 85.3 and 73.7%, respectively. The high-temperature tensile strength of the investment casting EN 1.4509 stainless steel sample is closely related to the bulk (Ti, Nb) (C, N) and the Laves phase (Fe2Nb) at the ferritic grain boundaries and in the ferritic grains. These are the main factors for improvement in the high-temperature strength of the tested steels; additionally, the coarse ferritic grains also play a certain role in improving the mechanical properties. The Nb content of the investment casting EN 1.4509 stainless steel can be reduced to 0.25 wt.%, and at this content, a combination of good high-temperature mechanical properties and higher room-temperature plasticity is obtained.