The thermal crack characteristics of rolled tungsten in different orientations

Thermal shock resistance of rolled tungsten with elongated grains aligned parallel and perpendicular to the loading direction was examined. Parallel (type A) or perpendicular (type B) grain orientations influences crack characteristics including threshold, profile, pattern and parameter. Type B samples show a cracking threshold of 0.44-0.66 GW/m2, which is much higher than type A samples (<0.22 GW/m2). For type A samples, primary cracks appear with linear profiles and dense secondary cracks along grain boundaries. Type B samples exhibit circular primary crack profiles as the homogeneous bending strength on the loaded surface and no secondary cracks are observed. Type A samples exhibit deeper cracking (550-850 μm) than type B samples (350-550 μm). The maximum crack widths were 2-8 μm for type A, again larger than those of type B (0-8 μm). Thermal fatigue tests were performed on type B samples, and cracks were detected after 1000 cycles.