Evaluation of crane wheels restored by hardfacing two distinct 13Cr-4Ni martensitic stainless steels

Abstract

Depositing two martensitic stainless steel filler metals with chemically different composition, crane wheels were restored to study the development of mechanical properties and wear resistance. For this purpose, a two-layer clad was deposited using each filler metal through submerged arc welding process. Microstructural evolution shows that solidification modes are different in the hardfaced clads due to the discrepancy in the ratio of chromium equivalent to nickel equivalent (Creq/Nieq). A reduction in Creq/Nieq leads to the enrichment of liquid metal in austenite-promoter elements, resulting in the presence of austenite phase in the matrix, as identified by XRD pattern. Following a post-weld heat treatment in the constant temperature of 500 °C for an hour, apart from the tempered martensite, fresh martensite as a consequence of transforming austenite phase is formed in the matrix. This transformation significantly increases the mean value of microhardness from 360 to 462 HV0.3. Also, uniaxial tensile test shows that the formation of fresh martensite approximately limits the elongation of the clad. The fractography studies show that the fracture mode in both clad is the same and ductile, with embedded carbides in dimples. Tribological behavior of the clads shows that the formation of fresh martensite in the clad results in higher wear resistance, with specific wear rate of 1.8 × 10−5 mm3/Nm at the maximum load. In addition, oxidative wear mechanism is dominant at lower load of 10 N, while the wear mechanism changes at higher load of 60 N to severe plastic deformation.

Keywords

• Fresh martensite
• Delta-ferrite
• PWHT
• Tensile strength
• Wear mechanism