[en] This relates to an anode assembly for rotating X-ray anode tubes, in particular to an anode disc comprising a graphite substrate. The substrate has two opposed major surfaces each with a central portion and an integral outer portion when related to the axis of the anode assembly. The anode target fixed to the substrate is tungsten or a tungsten-rhenium alloy. A single layer of metal joins the anode to the substrate; the metal is one in which carbon has almost zero solubility in the region 1000-1300⁰C but 1-4% solubility at the temperature of joining the anode target to the substrate. The metal layer has some solubility in the material of the anode target. It can be either rhodium, osmium, ruthenium, platinum, palladium or a Pt/1%Cr alloy, and is at least 0.5 mm thick. (U.K.)