Very Hard Corrosion-Resistant Roll-Bonded Cr Coating on Mild Steel in Presence of Graphite
- PDF / 3,372,018 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 71 Downloads / 187 Views
JMEPEG (2017) 26:5885–5896 https://doi.org/10.1007/s11665-017-3050-7
Very Hard Corrosion-Resistant Roll-Bonded Cr Coating on Mild Steel in Presence of Graphite Pankaj Kumar, S. Khara, S. Shekhar, and K. Mondal (Submitted June 12, 2017; in revised form September 9, 2017; published online November 3, 2017) The present work discusses the development of very hard Cr and Cr-carbide coating by roll bonding of Cr powder on a mild steel followed by annealing at 800, 1000, 1100 and 1200 °C with and without the presence of graphite powder packing in argon environment. In addition, the effect of a roll skin pass of 5% prior to the application of coating was studied. The presence of graphite allows diffusion of both carbon and Cr in the mild steel substrate, leading to the formation of Cr-carbide on the outer surface, making the surface very hard (VHN 1800). Depending on the annealing temperature and processing condition, diffusion layer thickness of Cr is found to be in the range of 10-250 lm with Cr content of 12.5-15 wt.% across the diffusion layer. Excellent stable passivity of the coated surface is observed in 0.2 N H2SO4, which is comparable to a highly passivating 304 stainless steel, and very low corrosion rate of the coating is observed as compared to the substrate mild steel. Keywords
corrosion, Cr coating, passivation, roll bonding
1. Introduction Mild steel finds large number of applications in the field of automobiles, household needs, pipelines, etc., because of its unique combination of properties, such as high ductility, formability, good weldability and economically highly viable. However, it possesses poor corrosion and wear resistance and low hardness. Therefore, coating seems to be a promising way to enhance these properties without affecting the bulk properties. Paints and organic coatings are mostly used for protecting structural steels, but they often fail due to their poor mechanical and chemical bonding with the substrate. In general, organic coatings have poor wear and high-temperature properties. Metallic coating seems to be a better option because of its good bonding ability with the base metal (Ref 1-4), good corrosion and oxidation resistance (Ref 5-9) along with excellent wear and abrasion resistance (Ref 10, 11). The major techniques for applying metallic coating on steel are chemical vapor deposition (Ref 12-14), electroplating (Ref 15, 16), thermal spray coating (Ref 17), hot dip galvanizing (Ref 18), cladding (Ref 19) and electroless plating (Ref 20). Generally, diffusion process across the interface between the substrate and the coating allows the coating to get bonded strongly, enabling the coating to possess excellent surface properties such as high oxidation resistance, corrosion and wear resistance. Hence, diffusion coating has become popular for protection against corrosion and wear. Diffusion of Cr has come to the limelight because of its inherent passivating tendency, leading to very high corrosion resistance. If Cr-rich surface coating is formed, it would give corrosion resistance
Data Loading...
