EFFECT OF PRE-HEAT TREATMENT ON FATIGUE BEHAVIOR OF SEVERE SHOT PEENED AND PLASMA NITRIDED AISI 4140 STEEL

Abstract

In this study, the pre-heat treatment applications (annealing, normalizing, oil quenching, tempering) influence is to be determined on the fatigue behavior of mechanically and thermally surface treated AISI 4140 low alloy steel. The plastically deformed, ultra fined and oriented grain layer has been created by means of severe shot peening and improved by pulsed plasma nitriding. The specimens were characterized by optical, scanning electron microscopy, X-ray diffraction and full width at half maximum (FWHM) analysis. The surface is investigated by surface roughness measurements before the understanding fatigue behavior of the specimens under different pre-heat treatments. The results demonstrate severe shot peening and plasma nitriding improves the fatigue limit of the material effectively. Also the combination of the treatments provides comparable fatigue limit of the annealed and normalized specimens compared to tempered one.

Keywords

• Severe Shot Peening
• Plasma Nitriding
• Fatigue
• FWHM
• Ultrafine Grain Layer