Wear resistant surface treatment of pulverizer blades

The pulverizer blade in food and animal feed production is subjected to abrasive wear from agricultural produce such as millet, corn, beans, rice husk and hull, resulting in the contamination of food by the wear debris from the blade material. This work compares different surface treatment and coating techniques used in improving the abrasive wear resistance of the blade, thus reducing the amount of contaminant. Four types of pulverizing blades were tested, namely flame hardened blade, hard Cr plated blade, plasma-sprayed Al2O3-TiO2 coated blade and HVOF-sprayed WC–Co coated blade. The dry abrasive wear test was carried out in a lab scale pulverizing test rig using rice husk as the abrasive media. The wear result, reported as the reduced area of the leading face, shows that the hard Cr plated-, Al2O3–TiO2 coated- and WC–Co coated blades display similar wear rates, which is lower than that of the flame hardened blade. When the weight loss of the blade was calculated from the wear volume and density of each blade, it was found that the Al2O3–TiO2 coated blade exhibits significantly lower weight loss due to its low density, rendering a lower mass of contaminant being released into the produce. The weight losses of the blades fitted in the inside position after 40 h of pulverizing test are 8.4, 3.7, 1.6 and 4.8 mg per one blade for flame hardened blade, hard Cr plated blade, Al2O3–TiO2 coated blade and WC–Co coated blade, respectively. These values were used to estimate the contaminant concentrations in rice husk.