The source and generated mechanisms of DS-size inclusions in bearing steel were studied by sampling systematically and using ASPEX, SEM and EDS to analyse the morphology, composition and amount of non-metallic inclusions larger than 13 µm. Two kinds of typical DS-size inclusions were found in the refining process: type I is CaO-MgO-Al2O3-SiO2 distributed evenly and wrapped by CaS; type II is composite inclusion with MgO-Al2O3 as the core, CaO-Al2O3 and CaO-SiO2 as the inner layer, covered by CaS. Based on the FactSage and thermodynamic calculations, the DS inclusions formation mechanisms were drawn. There are two formation mechanisms of the type II inclusions: one is the solid phases will precipitate from the matrix of type I inclusions as the temperature drops; another is that when the reaction time is not sufficient, the MgO∙Al2O3 spinel core will not be transformed completely, and the evolution can be summarized as: Al2O3 → MgO-Al2O3 → CaO-MgO-Al2O3 → surrounded by CaO-Al2O3(SiO2) → covered by CaS.

High‐carbon and high‐chromium alloy steels are prone to pitting and intergranular corrosion, which reduces corrosion resistance. The precipitation behavior of the carbides of high‐carbon and high‐chromium alloy steels is one of the main factors affecting pitting and intergranular corrosion of stainless steel. In this study, 5Cr15MoV stainless steel was heated to 1,200℃ and then cooled by cooling rates varying from 25 to 150°C/min. The precipitation behavior of grain boundary carbides of 5Cr15MoV steel at different cooling rates, and its effect on the corrosion resistance of materials was studied. The results show that the carbides of 5Cr15MoV steel mainly precipitate along the grain boundaries, which leads to the formation of chromium‐depleted zones near the grain boundaries and reduces resistance to intergranular corrosion. It has been found that a higher cooling rate shortens the width of the Cr‐depleted zone near the boundary from 0.871 to 0.569 μm, reduces the Cr‐concentration gradient near the grain boundary from 36.422% to 12.667%, and suppresses the nucleus growth rate of grain boundary carbides. As the cooling rate increases, the corrosion current density decreases from 13.29 to 2.42 μA/cm2. The corrosion rate is the lowest, while the cooling rate is 150°C/min. The corrosion rate decreases from 218.339 to 158.488 mm/a. The phenomenon of intergranular corrosion and pitting corrosion was found to be weakened; and thereby, it is shown that an intensive cooling rate can improve the corrosion resistance of 5Cr15MoV steel.

This study evaluated the effect of an increase in carbon content and the presence of the elements Mo and V on the microstructure and properties of the surfacing layer of stainless steel powder for knives and scissors production. Various types of high-quality stainless steel powder (5Cr 13 , 8Cr 13 , and 8Cr 13 MoV) were deposited on the surface of low-grade stainless steel used to produce knives and scissors (2Cr 13 ). The microstructure, comprehensive hardness, wear resistance, impact toughness, and corrosion resistance of the stainless steel powder surfacing layers were tested and analyzed. Results indicate that the increase in carbon content and the presence of Mo and V improve the comprehensive hardness and wear resistance of the stainless steel powder surfacing layer, and both exert the superposition effect. However, the increase in carbon content and the presence of Mo and V slightly influence the impact toughness of the surfacing layer. In addition, the increase in carbon content significantly reduces the corrosion resistance of the surfacing layer. This adverse effect is reduced when Mo and V exist. Other advantages of the presence of Mo and V in the stainless steel powder surfacing layer include the refinement of grain size, reduction of carbide particle size, and improvement of the metallurgical bonding of the surfacing layer and the matrix.Coatings 2020, 10, 371 2 of 16 barber tools, which are seldom used in daily life. Therefore, to manufacture high-quality knives and scissors that can be used by the general public, this study explores a method to produce such instruments by plasma surfacing. The surfacing layer obtained by plasma surfacing can achieve large thickness [20,21]. This characteristic is used for surfacing powders of high-grade materials for knife and scissors production on the surface of massive low-grade materials for knife and scissors production. The composite material is then longitudinally cut. The thicker surfacing layer is directly used to produce the edge of knives and scissors, while the matrix (low-grade materials) is used to produce the body of knives and scissors. The method belongs to local strengthening of knives and scissors. The advantage of this method is that only the edge of a knife or scissors is mainly forced and abraded during use [22][23][24]; most high-grade materials are in an idle state of inaction. Limiting the use of high-grade materials to the production of the edge of a knife or scissors can not only meet the requirements for knife and scissors production but also reduce waste (of high-quality materials) and limit costs. However, no studies have been reported on surfacing high-quality stainless steel powder for knife and scissors production, and no methods have been developed to evaluate the microstructure and properties of the surfacing layer of high-quality stainless steel powder for such production.This study mainly aims to explore the microstructure and properties of the surfacing layer of high-quality stainless steel powder for knife and scissors product...

The excellent mechanical properties of Inconel 718 are due to the γ′ and specifically the γ′′ precipitates. Solution heat treatment was performed at 1095 ºC for 1 h followed by air cooling. A δ-phase precipitation heat treatment was made at 955 ºC, 1 h/AC. Finally a double-aging at 720 ºC, 8 h/FC at 57 ºC/h down to 620 ºC, 8 h/AC to precipitate both γ′ and γ′′ phases. The precipitation of both γ′ and γ′′ phases were studied in details after aging treatment by the use of transmission electron microscopy. The spherical precipitates were identified as γ′ phase and the ellipsoidal precipitates were γ′′ phase. At 720 ºC for 8 h both γ′ and γ′′ are growing; the mean long-axis of γ′′ particle is 40 nm and the mean short-axis is 14 nm whereas the average diameter of the spherical γ′ particle is 17 nm. However, at 620 ºC, γ′′ stops growing but γ′ continue to grow and the diameter increases to 21 nm.