Microstructural studies of QPQ complex salt bath heat-treated steels

Effect of Salt Bath Nitrocarburizing and Post-Oxidation on Static and Fatigue Behaviours of a Construction Steel

“…The liquid nitrocarburizing in salt bath has been widely employed in industry since the 1940s; however, this method had a major issue related to toxicity of the cyanide-cyanate salt, which was solved in 1970 [11] by adopting a nontoxic cyanate-bearing bath. Later on, in the 1980s, an advanced salt bath heat treatment, given by the combination of nitrocarburizing and post-oxidation, known also as quench-polish-quench (QPQ) treatment, has been proposed and, then, widely employed in industrial applications, since it was demonstrated that the additional process of post-oxidation after nitrocarburizing further enhances the mechanical properties of the treated materials [12][13][14][15][16][17][18].…”

“…In previous contributions, several authors have analysed the effect of nitrocarburizing on the fatigue limit of the plain material [26][27][28][29][30][31], while only few contributions [10,24] have been devoted to investigating the effect of nitrocarburizing on the medium-high cycle fatigue regime, considering both plain and notched specimens. Moreover, the effects of the combination of salt bath nitrocarburization and post-oxidation, i.e., QPQ treatment, have been mainly analysed from the point of view of microstructure, hardness, wear and corrosion resistance [14][15][16][17][18]32], while the effects of QPQ treatment on the fatigue behaviour have been investigated in detail only for some steel categories, such as carbon steels [33][34][35], alloyed steels [36,37], tool steel [38]; and also for ductile cast iron [39].…”

The Influence of Salt Bath Nitriding Variables on Hardness Layer of Aisi 1045 Steel

“…The most important and oldest method of thermo chemical surface hardening operation is nitriding operation of steel which changing the chemical properties of the surface layer [12]. Salt bath nitriding is developed as an industrial process, especially for surface modification of iron-based steels; this process technology has solved environmental problems and can be applied DOI 10.12776 to AISI 1045 steel and high alloy steels with high reaction efficiency [13][14]. Salt bath nitriding is done to obtain high surface hardness, to increase wear resistance, to improve fatigue life, and to improve corrosion resistance, high dimensional stability [15][16].…”

Effects of nitrocarburizing on fatigue property of medium carbon steel in very high cycle regime

“…Lu). bination of salt bath and post-oxidization is performed to further enhance the properties [5][6][7][8][9]. It is well known that the improvement of fatigue strength is mainly due to the diffusion layer formed beneath the compound layer and the surface compress residual stress [2].…”