Investigation of the effects of microstructural changes on the mechanical properties, corrosion, and wear resistance of CD4MCuN and 1.4468 grade duplex stainless steel

Duplex stainless steels offer high mechanical strength and corrosion resistance due to the simultaneous presence of austenite and ferrite phases. Thanks to these characteristics, they are preferred in industries such as marine, mining, and petroleum. For optimal properties, it is desirable to maintain a balanced ratio between the austenite and ferrite phases. However, secondary phases like sigma (σ), chi (χ), Cr2N, and CrN, which form alongside the primary phases, generally reduce mechanical properties and represent a major challenge in the production of duplex stainless steels. This study investigates the production of CD4MCuN and 1.4468 grade duplex stainless steels via casting and examines how the microstructural changes occurring during the process impact mechanical properties, corrosion resistance, and wear resistance. After solution heat treatment of the cast parts at 1050-1150°C, microstructural analyses were performed using optical microscopy (OM), XRD and scanning electron microscopy (SEM) to determine phase ratios and the presence of secondary phases. Hardness, tensile strength, impact toughness, and wear resistance were tested, and the effect of varying heat treatment temperatures on the microstructure and corresponding mechanical properties was analyzed. Additionally, the influence of phase ratios on the corrosion resistance of duplex stainless steels was assessed through potantiodynamic tests in chlorinated environments (%3,5 NaCl). In conclusion, it has been observed that microstructure is directly related to mechanical properties, with samples having a ferrite-to-austenite ratio close to 1:1 generally achieving optimal values. However, properties such as corrosion resistance have shown a decline due to the presence of secondary phases.