|Hard metal coating|
Fiehl+Cremer the hard metal coating specialist based in Lüdenscheid. Two coating systems are used in hard metal coating for thermal spraying / flame spraying.
1. For hard metal coatings with powder flame spraying and self-fluxing according to DIN EN ISO 14920 mostly powder raw materials based on NiCrBSi alloys with addition of Wolfram carbide or chrome carbide are used.
The particles have a hardness of ca. 75HRc/2300HV and keep their hardness during the welding process too. Furthermore, with WSC-mix ( Wolfram welding carbide ) and a grain size distribution of 20µm -100µm a hard metal coating can be applied.
Those additives are mixed into the self-fluxing NiCrBSi alloy between 20% - 50% and build - with the later sintered at ca. 1000°C - the most gas tight and also least knock sensitive hard metal coating of the thermal spraying. The hard metal coating can be applied up to ca. 550°C and then the self-fluxing NiCrBSi alloy slowly loses its basic hardness of ca. 60HRc.
2. Hard metal coating with HVOF has a larger material selection then powder flame spraying. During this wrapped Wolfram carbide cobalt or chrome carbide nickel chrome alloys are mostly used. This hard metal coating can also be applied up to ca. 550°C.
At higher temperatures the alloy loses solidity due to phase transformations, but also due to possible underlying corrosion in various media and failing sealing. This hard metal coating is applied with the WC/Co/Cr alloy as hard chrome replacement in electro plating, whereby the coating material in HVOF should be considered in many areas of electro plating.
High speed flame spraying With the addition WC/Ni the hard metal coating becomes clearly more corrosion resistant, whereby WC/Co shows a higher temperature resistance.
PTFE or graphite can also be mixed in the alloy. This HVOF hard metal coating thus achieves improved anti adherent and sliding features.