Influence of grain size on the corrosion/wear behaviour of HVAF sprayed Fe-based coatings

In large area applications, cylinders for paper machines or piston rods are often loaded by corrosion/wear and therefore, they need an adequate surface protection. The goal of this study is to develop a cost efficient coating system which protects the surface in these applications as effectively as the industrially established hard chrome or high velocity oxygen-fuel (HVOF) sprayed cemented carbide coatings. Cost efficiency is to be achieved through the use of an economically priced Fe-based feedstock material and the high velocity air-fuel (HVAF) process with high powder feed rates up to p > 200 g/min. A further aspect is the reduction of the post-production time and costs, which can be achieved by the production of thin and near-net shape coatings.

In this study the Fe-based feedstock material, with two grain size fractions of
-45 +11 µm and -20 +3 µm were used to investigate the influence of grain size on corrosion/wear properties of coatings applied by means of HVAF spraying. The corrosion and wear properties were investigated using polarization and pin-on-disc tests. XRD- and REM-measurements were used to investigate the phase composition and microstructure of the coatings. The results indicate a significant correlation between grain size fraction and corrosion/wear properties.