Method of providing a metal component with a thermally black surface

DETAILED DESCRIPTION I claim: 1.
A method of providing a thermally black surface on a substrate comprising the steps of: forming a layer of a metal compound on said substrate, said metal compound comprising aluminum and at least one of molybdenum, nickel, iron, tungsten and copper; and oxidizing part of the aluminum from said metal compound.
2.
A method as claimed in claim 1, characterized in that the step of oxidizing comprises oxidizing substantially all of the aluminum from the metal compound.
3.
A method as claimed in claim 2, characterized in that the step of forming the layer of metal compound comprises: coating the substrate surface with a layer comprising aluminum and at least one of molybdenum, nickel, iron, tungsten and copper; and heating the coated substrate in a nonreactive atmosphere to produce a compound of aluminum with at least one of molybdenum, nickel, iron, tungsten, and copper.
4.
A method as claimed in claim 3, characterized in that the coating consists essentially of aluminum and at least one of molybdenum, nickel, iron, tungsten, and copper.
5.
A method as claimed in claim 2, characterized in that the step of forming the layer of metal compound comprises: providing a substrate having a surface comprising at least one of molybdenum, nickel, iron, tungsten, and copper; coating the substrate surface with a layer of aluminum; and heating the coated substrate in a nonreactive atmosphere to produce a compound of aluminum with at least one of molybdenum, nickel, iron, tungsten, and copper.
6.
A method as claimed in claim 5, characterized in that the substrate surface consists essentially of at least one of molybdenum, nickel, iron, tungsten, and copper.
7.
A method as claimed in claim 4 or 6, characterized in that the step of oxidizing is performed by firing the coated substrate at 950.
degree.
C.
to 1200.
degree.
C.
in a wet hydrogen atmosphere, and the layer is from one to a few microns thick.
8.
A method of making a deep-drawn cathode shaft having an inside surface which is thermally black, said method comprising the steps of: providing a planar substrate; and providing a thermally black surface on the substrate by the method of claim 7; characterized in that prior to the step of oxidizing, the substrate is deep-drawn