Magnetic disk comprising a substrate with a cermet layer on a porcelain

A method for making a magnetic recording disk, comprising the steps of:

• (a) providing a disk-shaped substrate made of a porcelain comprising one or more crystalline oxide phases dispersed in a glassy matrix, the glassy matrix containing 0.25 to 45.0 weight % of a reducible metal oxide having a reduction potential of between -1.0 and +3.5 E.degree./V, the weight % of the reducible metal oxide being based on the weight of the porcelain;
• (b) heating the substrate in a reducing atmosphere to form on a planar surface thereof a layer of cermet comprising elemental metal which is a reduction product of the reducible metal oxide;
• and
• (c) superposing a layer of a magnetic recording medium over of the layer of cermet.