THE EFFECT OF BORONIZING ON HARDNESS, WEAR AND CORROSION PROPERTIES OF AISI 1018 AND AISI 316L STEELS

Steels are widely used in potash processing, but they show unsatisfactory performance under severe corrosion and wear conditions. Boronizing heat treatment is a good method to improve surface properties of steels used in potash processing. However, there is dearth of information on research works in the open literature focusing on the effect of boronizing on corrosion of steels used in potash processing plants. In the present study, AISI 1018 and AISI 316L steels were case-boronized at temperatures of 850 °C, 900 °C and 950 °C for 4 h, 6 h and 8 h. The effect of boronizing conditions on boride layer thickness, hardness and boride phase evolution were investigated using hardness, surface roughness and thickness measurements, X-ray diffraction, optical microscopy and scanning electron microscopy. The wear, general corrosion and erosion-corrosion resistance of the boronized steels were evaluated using a pin-on-disc wear test apparatus, electrochemical corrosion measurements, and a flow loop apparatus, respectively. It was found that boronizing provided significant improvement in surface hardness and wear resistance for both AISI 1018 and AISI 316L steels. It was also found that the boride layer formed on the surface of AISI 1018 steel worked as a protective layer to reduce its corrosion rate in both saturated KCl and saturated raw potash solutions. However, boronizing did reduce the corrosion resistance of AISI 316L steel in both solutions, probably due to increase in porosity observed in the boride layer formed on it. The results of erosion-corrosion experiments showed that boronizing was effective in improving the erosion-corrosion resistance of AISI 1018 steel in saturated potash-silica sand slurry