Diffusion Behavior at the Interface of Cladding Steels

Abstract

Various cladding materials consisting of plain carbon steels with lower carbon concentrations and alloy steels with higher car bon concentrations have been considered to analyze the behavior of interdiffusion across the interface theoretically. The combina tion of the plain carbon steel and the alloy steel for the cladding was selected to make the chemical potential of carbon greater in the plain carbon steel than in the alloy steel. For the selection, the phase diagrams were computed with Thermo_ Calc. The theo retical analysis was carried out using DICTRA that is the software developed at the Royal Institute of Technology in Sweden. The analysis indicates that the up_ hill diffusion of carbon spontaneously occurs from the plain carbon steel to the alloy steel dur ing annealing at elevated temperatures. For example, the cladding material composed of a plain carbon steel with a concentration of 0.046 mass÷C and a 18Cr_ 8Ni stainless steel with a concentration of 0.06 mass÷C exhibits such an up_ hill diffusion at 1200 K, resulting in precipitation of Cr 23 C 6 at the cladding interface.

Interfacial microstructure observation and nanoindentation measurements in mild steel/HT780 clad plate

“…7,8 When a thin stainless steel plate is clad with mild steel, for example, the precipitate carbides that form near the interface improve the resistance to corrosion and abrasion. 9 In contrast, carburising reportedly causes stress corrosion cracking at a clad steel interface. 6 Studies of clad materials found in the literature often focus on mild steel and stainless steel, and as of yet, there are no reports regarding the cladding of mild steel and high strength steel.…”

“…The characteristics of the clad steel depend on the type of intermediate layer formed at the interface of the two metals through elemental diffusion, which is primarily determined by the preheating process 7,8. When a thin stainless steel plate is clad with mild steel, for example, the precipitate carbides that form near the interface improve the resistance to corrosion and abrasion 9. In contrast, carburising reportedly causes stress corrosion cracking at a clad steel interface 6.…”