A rotary anode of an X-ray tube delivers X-rays from at least the surface struck by electrons and consisting mostly of molybdenum. According to the present invention this surface consists to at least 90 percent of molybdenum and up to 10 percent hafnium.

Rotary anodes for X-ray tubes are provided having improved thermal stability. The rotary anodes are comprised of a basic body made of molybdenum alloy comprising about 0.1 to 15% by weight hafnium, about 0.1 to 15% by weight zirconium, about 0.01 to 1.0% by weight carbon and the balance molybdenum. The alloy according to the invention has a low tendency of cracking distortion, and/or surface roughening, even with focal track zones made of tungsten and tungsten alloys and even at operating temperatures exceeding the currently normal values by up to about 200.degree. C.

An X-ray tube includes a rotary anode structure having a rotary target. The target includes an electron receiving layer made of a tungsten based alloy and a substrate made of a molybdenum based alloy containing titanium and/or zirconium in an amount of 0.5 to 2.0% by weight.

An X-ray tube anode which is composed of a refractory metal having a focal track thereon with the refractory metal including tantalum, hafnium, zirconium and carbon in a minor amount and molybdenum in a major amount. The anode has improved high temperature properties and fabricability. It can be utilized alone or in combination with the usual graphite portion.

Rotary targets for X-ray tubes are provided comprising a molybdenum base body alloyed with a stabilizing proportion of iron, silicon, cobalt, tantalum, niobium, hafnium, stable metal oxide, or a mixture of the preceding.