Abstract
The effects of the nitrided case produced by gas nitriding processes on the mechanical and corrosion resistance properties of the JIS SACM 645 steel were studied in this paper. JIS SACM 645 steel specimens with different substrate hardness were gas nitrided at 530?C for various nitriding durations. Nitrided specimens were characterized by means of optical and scanning electron microscopy, X-ray diffraction, glow discharge optical spectrometry, microhardness profiling, wear test, torsion mode fatigue test as well as electrochemical corrosion test in an aerated 3.5% NaCl solution. The surface hardness values of the nitrided specimens with Fe3N and Fe4N phases precipitated in the case layer were observed higher than 1000 HV0.1. Mass loss measurement of the wear test showed increases of wear resistance of the nitrided specimens, and the mass losses of the specimens were strongly influenced by nitriding durations. Electrochemical measurements showed that corrosion current density of the specimens was significantly decreased after nitriding and the corrosion potential was shifted to the noble direction as the increase of the nitriding durations. The fatigue limit of the specimen nitrided for 96 h rose 44% to 600 MPa in exceeding the untreated specimen in this study.
Highlights
The positive effects of surface treatments like nitriding on the fatigue and wear properties of structural steel have been known for several decades
Wear test data indicated that the mass loss of JIS SACM 645 steel was greatly improved by nitriding processes and the wear resistance of the nitrided specimens was significantly improved by extending nitriding duration
The fatigue limit of the SACM450 steel was greatly improved by nitriding process
Summary
The positive effects of surface treatments like nitriding on the fatigue and wear properties of structural steel have been known for several decades. The structural steel of those components should be always surface modified to provide these needed properties The surfaces of these components are required to attain high hardness values to resist wear, and the inner cores still need to have high toughness strength [1,2]. Various methods, such as nitriding, carburizing, ceramic coating and thermal chemical treatments, have been devised to improve the surface mechanical properties of the components [3,4,5]. The aim of present study is to investigate the effects of different gas nitriding parameters on the mechanical and corrosion properties of the SACM 645 steel, as well as the effect of the substrate hardness on the wear, fatigue and corrosion properties of nitrided SACM 645 steel specimens
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