Hot Extruded High-Temperature Alloy Tubes and Some Mechanical Properties

Seamless hot extruded tubes serve as structural materials of high-temperature gas-cooled reactors and coal conversion systems with exposure temperatures up to 1000°C. The tube dimensions (∼130- × 15-mm diam) were produced according to the proposed requirements for methane reformer heat exchangers of nuclear process gas production systems. The most sensitive extrusion parameter is the temperature of the expanded billet at the press, where it should reach 1140 to 1180°C depending on the materials investigated: Incoloy-800H, Incoloy-802, Hastelloy-X, Inconel-617, and Nimonic-86. To qualify the extrusion products, the mechanical properties obtained from tensile tests at room temperature and temperatures up to 1000°C are compared for tube products. Strengthening effects at 800°C are explained by carbide precipitation during the test, especially of alloys 800H and 802.