Hochtemperatur-Verschleißverhalten von thermisch gespritzten Hartmetallschichten für Ventilspindeln in Dampfturbinen (High-Temperature Wear Behavior of Thermally Sprayed Cemented Carbide Coatings for Valve Spindles in Steam Turbines)

Thermally sprayed hardmetal coatings are often used to protect valves in steam turbines against wear. Normally the valve spindles are made of CrMo steel and their bearings are made of Stellite, a cobalt-base alloy. In this investigation, a block-on-ring wear test is used with rings and blocks made of the same materials as the spindles and bearings. The rings were coated with Cr3C2-NiCr by HVOF spraying. Wear tests showed increasing weight loss up to 400°C and a sharp decline at 600°C due to a thin surface oxide layer that begins growing at 450°C. The coatings are characterized based on SEM, EDX, and hardness measurements. Paper text in German.