HVOF sprayed WC/Co(Cr) and Cr 3 C 2 /Ni20Cr composite coatings have gained high acceptance in many industrial applications for protection of components against wear. The achieved coatings have quite good corrosion resistance for use of chromium containing matrices. Present research in the field of PTA-Surfacing resulted in the development of high chromium and high vanadium containing iron based hard alloys with simultaneous improvement of abrasive wear and corrosion resistance. These properties of the PTA-Surfaced coatings were studied and it was found that the newly developed alloys have nearly same wear resistance and improved corrosion resistance compared to Co-based alloys reinforced with Fused Tungsten Carbides (FTC). One major advantage of high chromium and high vanadium containing iron based coatings is machinability by turning and milling processes. These features make it attractive to be used in thermal spraying. The absence of substrate melting in HVOF-spraying is advantageous, as the coatings preserve the properties of the alloy due to prevention of dilution with substrate material in contrast to PTA-Surfacing. High chromium and high vanadium containing iron based atomized powder was used for HVOF spraying and deposition efficiency was measured. The sprayed coatings were studied metallographically by optical microscopy, SEM, XRD and micro-hardness measurements. Later, abrasive wear and corrosion properties of the coatings are investigated.

Aluminium alloys are extensively used materials which can be found in all kinds of industrial applications. They have distinctive advantages such as a high strength/weight ratio, an excellent workability and a good corrosion behaviour. However, aluminium alloys have wear resistance properties which limitate further use of these alloys. Plasma transferred arc surfacing (PTA) using the DCCP-technology (Direct Current Combined Polarity) was used for enhancing wear properties of different aluminium alloys (AlMgSi0.5, AlSi12) by the formation of an alloyed layer with added ceramics. Hardness of the base material could be increased by more than two times while the wear resistance of the modified aluminium alloy was about ten times higher compared to the base material. Paper text in German.