Influence of crystallographic orientation on the mechanical properties of single crystals of Ni3Al-based alloys

An alloy based on Ni3Al with additions of chromium, molybdenum, tungsten, titanium, hafnium, iron and carbon has a density of 7.91 g/cm(3) and is highly resistant to oxidation at 1200 degrees C: the increase in its mass after 100 hr of oxidation is 16 g.m(-2). Single crystals of orientation [001], [011], [111] containing up to 10% gamma phase are obtained by high-gradient directional crystallization. The temperature dependence of the short-term and long-term (up to 500 hr) strength of single crystals of different orientation is investigated at 900-1200 degrees C. At room temperature, single crystals of orientation [111] have a short-term strength of 1320 MPa, 14% elongation, and an impact ductility of 38 J.m(-2). Single crystals of orientation [111] have the maximum 100-hr strength: sigma(100) = 380, 220, 110, and 50 MPa in air at 900, 1000, 1100, and 1200 degrees C, respectively. The high stability of the structure formed on crystallization in long-term tests under load is shown.