Abstract
Stainless steel-based WC composite layers fabricated by a laser cladding technique, have strong mechanical strength. However, the wear resistance of WC composite layers is not sufficient for use in severe friction and wear environments, and the corrosion resistance is significantly reduced by the formation of secondary carbides. Low-temperature plasma nitriding and carburizing of austenitic stainless steels, treated at temperatures of less than 450 °C, can produce a supersaturated solid solution of nitrogen or carbon, known as the S-phase. The combined treatment of nitriding and carburizing can form a nitrocarburizing S-phase, which is characterized by a thick layer and superior cross-sectional hardness distribution. During the laser cladding process, free carbon was produced by the decomposition of WC particles. To achieve excellent wear and corrosion resistance, we attempted to use this free carbon to form a nitrocarburizing S-phase on AISI 316 L stainless steel-based WC composite layers by plasma nitriding alone. As a result, the thick nitrocarburizing S-phase was formed. The Vickers hardness of the S-phase ranged from 1200 to 1400 HV, and the hardness depth distribution became smoother. The corrosion resistance was also improved through increasing the pitting resistance equivalent numbers due to the nitrogen that dissolved in the AISI 316 L steel matrix.
Highlights
Laser cladding is an effective method for surface modification, such as improving the wear and corrosion resistance of metal substrates, and has many advantages, such as high deposition speed with rapid cooling, dense metallography, strong bonding strength between the cladding layer and substrate, low heat input, and distortion of the substrate [1].In recent years, the fabrication of three-dimensional objects by additive manufacturing (AM) using laser as a heat source has attracted much attention
Thehas ni-the trocarburizing S-phase was formed by the composite of the wt.% of tungsten carbide (WC) particles, that has the advantage of smoothing the hardness depth distribution, which is expected to restrict the delamination of the S-phase layer from the substrate when an external force is applied
The 9niof 13 trocarburizing S-phase was formed by the composite of the WC particles, that has the advantage of smoothing the hardness depth distribution, which is expected to restrict the delamination of the S-phase layer from the substrate when an external force is applied advantage of smoothing the hardness depth distribution, which is expected to restrict the delamination of the S-phase layer from the substrate when an external force is applied [50]
Summary
Laser cladding is an effective method for surface modification, such as improving the wear and corrosion resistance of metal substrates, and has many advantages, such as high deposition speed with rapid cooling, dense metallography, strong bonding strength between the cladding layer and substrate, low heat input, and distortion of the substrate [1]. As a matter the WC particles composite for AISI 316 L stainless steel layers obtained by the laser cladding process leads to improved mechanical properties, in particular, surface hardness and wear resistance [21,22,23]. A combined treatment of nitriding and carburizing has advantages of thickening and improving the toughness of the S-phase compared with the individually nitriding and carburizing [36,37,38,39] These plasma treatments have been applied to steel plates and to thermal spray coatings and laser cladding of AISI 316 L stainless steel, and their effectiveness has been recognized by the authors [27,28,29,30]. The formation mechanism of the nitrocarburizing S-phase by low-temperature plasma nitriding were investigated, and the properties of the hardness and corrosion resistance with the WC content were discussed
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