Continuous impact wear resistance of duplex surface-modified hot work tool steel H10

An alternative possibility to increase exposure time of hot work tools is the modification of the tool's surface. The most common method of surface modifying for this kind of tools is nitriding. Unfortunately, nitrided cases often suffer from severe impact wear. Therefore, the development of graded surface layers for backing of the nitrided cases by hard metal monocarbides like TiC, Cr3C2, WCCo and WCCoCr, alloyed in the tool's surface could be promising. To cut back expensive production trials, impact wear tests of the duplex-coatings were carried out by a special apparatus where a fixed tungsten carbide ball periodically stroke on the specimens' surface. In time, an indentation dome was developed which could be evaluated by its diameter. Results have shown that the best impact wear resistance is provided by duplex-layer WCCoCr-plasmanitrided. After the laboratory experiments some of the duplex-layers were tested on simple high speed forging tools for screw-production. With duplex-layer WCCoCr-plasma a 50% increase of tool life time was achieved, though the transferability of laboratory experiment and industrial application proved to be rather unsteady.