Performance of plasma-sprayed MoSi2-based coating as a heating element

Rollers covered with a thermally sprayed heater coating are an alternative to conventional stream heated and electromagnetic induction heated rollers. In this study, a heater coating was developed using a combination of a thermally sprayed NiAl bonding layer, an MgAl2O4 insulating layer, and an MoSi2-based conductive layer; for comparison, an optional thin MgAl2O4 top layer was applied to provide corrosion and wear protection. The microstructures and characteristics, particularly the electrical-thermal performance, were systematically investigated. The MgAl2O4 layer was found to provide excellent high-temperature insulation performance. Thermo-cycling tests indicate the MoSi2-based coating can be heated to 320 degrees C with a relatively uniform temperature distribution at the roller surface. The addition of the top layer as a protective mask is beneficial to the heating stability, and NiCr added as a bonding phase in the conductive layer significantly improves the electrical-thermal performance.