Abstract: A method for increasing the wear-resistance of a work piece involves connecting the work piece to a non-formable core material having a greater hardness than that of the work piece material. In order to improve the connection while simultaneously reducing the costs, the core material is connected in a form-fitting manner to the work piece by means of cold extrusion or hot extrusion of the work piece material.

Abstract: A valve disk of silicon-infiltrated silicon carbide material for control elements for regulating liquid flows is suitable in particular for service-water mixer valves. The silicon carbide material contains 70 to 90% by weight of silicon carbide and 8 to 30% by weight of silicon with a content of most 0.2%, by weight of free carbon and contains at most 0.1% by volume of closed pores. The valve disk has a functional surface having the optical appearance in the form of isolated islands of bearing surfaces surrounded by a level lying lever with respect to the isolated islands, the functional surface having the following microtopographical characteristics over its entire region: R.sub.a : 0.02 to 0.80 .mu.m, preferably 0.15 to 0.40 .mu.m; R.sub.t : 0.50 to 6.00 .mu.m,; R.sub.z : 0.20 to 100 .mu.m: flatness: 0.0002 to 0.01 mm; t.sub.pi : 40 to 80% (at 0.3 .mu.m cut depth); t.sub.pa : 10 to 60% (at 0.3 .mu.m cut depth). The invention also relates to a process for producing the valve disk.