Filament Sprayed (F-HVOF) NiCr Resistant Heater Coatings

The worldwide breakover from fossil fuels to renewable energy demands energy efficient technological solutions. In many fields, especially the transportation industry, batteries are the alternative to combustion engines. However, batteries do not produce waste heat and are temperature sensitive exhibiting a significantly reduced performance at low temperatures. Resistant heater coatings pose an attractive solution as they allow fast and precise electrical heating. Within this study resistant heater coatings are developed via filament high velocity oxy fuel spraying (F HVOF) using a Ni-Cr filled Polypropylene filament as feedstock material. This novel technology allows spraying of fine powders similar to suspension spraying, but a polymer is used as solid transport medium instead of a liquid phase. Dense coatings with a homogenous microstructure and a thickness of 20 to 30 µm are fabricated. Thus, allowing a fast and uniform heating with a low energy consumption and long product life cycle. The coatings are sprayed as meander pattern onto steel substrates and characterized regarding their microstructure, oxide content and electrical conductivity. The heating profile is evaluated using a thermal camera. Further, the heating rate and cycle stability are determined.