Tungsten Alloy Fiber Reinforced Nickel Base Alloy Composites for High-Temperature Turbojet Engine Applications

Abstract

The potential of tungsten-2 percent thoria, 218 tungsten, and tungsten-1 percent thoria wire reinforced nickel-base superalloy composites for turbine bucket applications was evaluated based on stress-rupture strength, oxidation, and impact resistance. The results indicate that refractory metal alloy fiber-superalloy composites have potential for turbine bucket use based on the properties measured. Composites were produced having stress-rupture properties superior to conventional cast superalloys at use temperatures of 2000 and 2200 F. The 100 and 1000-h stress-rupture strength of the composite at 2000 F was 49,000 and 37,000 psi, respectively. A few thousands of an inch of matrix or cladding material was found to be sufficient to protect the fibers from oxidation at 2000 F for times up to 300 h. At 300 F and above the impact resistance of the composite compares favorably with that of superalloys.

Latest Developments to Manufacture Metal Matrix Composites and Functionally Graded Materials through AM: A State-of-the-Art Review

“…In MMC material systems, the metallic phase serves as a binder to the composite, while the ceramic phase acts as the reinforcement. MMCs emerged in the 1960s to further improve the mechanical properties of structural superalloys for applications related to defence and aerospace [ 104 , 105 ]. Later, in 1991, the suitability of these materials for the surface modification of components exposed to critical erosion and wear conditions was established [ 106 ].…”

Design Concepts for Fiber-Metal Matrix Composites for Advanced Gas Turbine Blades

“…At the high-temperature level of 2000 F, relatively little has been done with fibers or with composites. In work conducted at the Lewis Research Center, experience with high-temperature composites has been encouraging (16,17). For example, one composite composition with M42Th0 2 fibers has been made with a strength-to-density ratio of 60,000 in, for 1000 hr at 2000 F (17).…”

Stress-rupture strength and microstructural stability of W-Hf-C wire-reinforced superalloy composites

“…Previous work at the Lewis Research Center demonstrated that 70 volume percent fiber composites could be produced to have 100-and 1000-hour rupture strengths at 10900 C (20000 F) of 338 and 255 MN/m 2 (49 000 and 37 000 psi) (Ref. 5). Figure 1 is a plot of the 1000-hour stress-rupture strength divided by the material density as a function of temperature for superalloys and for a tungsten-2 percent Th02/superalloy composite having a fiber content of 70 percent by volume.…”