Effect of Chromium on Microstructure and Oxidation Wear Behavior of High-Boron High-Speed Steel at Elevated Temperatures

Abstract

In order to investigate the effect of Cr content on the microstructures and oxidation wear properties of high-boron high-speed steel (HBHSS), so as to explore oxidation wear resistant materials (e.g., hot rollers), a scanning electron microscope, an X-ray diffractometer, an electron probe X-ray microanalysis and an oxidation wear test at elevated temperatures were employed to investigate worn surfaces and worn layers. The results showed that the addition of Cr resulted in the transformation of martensite into ferrite and pearlite, while the size of the grid morphology of borides in HBHSSs was refined. After oxidation wear, oxide scales were formed and the high-temperature oxidation wear resistance of HBHSSs was gradually improved with increased additions of Cr. Meanwhile, an interaction between temperature and load in HBHSSs during oxidation wear occurred, and the temperature had more influence on the oxidation wear properties of HBHSSs. SEM observations indicated that a uniform and compact oxide film of HBHSSs in the worn surface at elevated temperatures was generated on the worn surface, and the addition of Cr also reduced the thickness of oxides and inhibited the spallation of worn layers, which was attributed to improvements in microhardness and oxidation resistance of the matrix in HBHSSs. A synergistic effect of temperature and load in HBHSSs with various Cr additions may dominate the oxidation wear process and the formation and spallation of oxide films.

Effect of Silicon Content on Microstructures and Properties of Directionally Solidified Fe-B Alloy

“…Obviously, on one hand, Si may promote the solid solution of Cr atoms in the matrix, resulting in more (Fe-Cr) substitutional solid solutions, and on the other hand, Si is likely in favour of forming the depletion or segregation at the ferrite/boride boundaries to refine the columnar structure of the DS Fe-B alloy, which may be attribute to the constitutional supercooling effect and the outcome of Cr substitutional solid solution caused by the role of Si [ 27 , 28 , 29 ]. Actually, phase boundary segregation and matrix solution of Si may also adjust the Cr in the microstructures of Fe 2 B and α-Fe to promote the replacement of Fe atoms by Cr atoms in borides, likely forming some Cr-rich borides, as the changes of the boride peaks in XRD [ 37 ]. Obviously, the detected peaks of the transverse section in the DS Fe-B alloy comprise the only (002) crystal plane of the Fe 2 B and very strong (110) crystal plane of the α-Fe and both of these peaks are relatively strong ( Figure 4 c), whereas more peaks of Fe 2 B in the longitudial section appear ( Figure 4 a).…”

Effects of Boride Orientation and Si Content on High-Temperature Oxidation Resistance of Directionally Solidified Fe–B Alloys

“…With an increase in Si content, the inside of the oxide film became denser, preventing the outward diffusion of the internal matrix elements, and the surface became flatter. From Figure 8 , the surface oxides of sample A1 were composed of Fe 2 O 3 , M 3 O 4 (M = Fe, Cr) [ 41 ]. It is interesting to note that a small amount of SiO 2 was obtained on the surface of the oxide film, which indicates that part of the Si may segregate at the substrate–scale interface and react with oxygen ions to form the inner SiO 2 layer.…”

Effects of sintering temperatures on the microstructure and mechanical properties of S390 powder metallurgy high-speed steel

“…The high-vanadium HSSs were prepared, and the highest wear coefficient of specimens sintered at 1,250 °C was 4.31 × 10 −15 m 2 /N (Wan et al, 2019). The 10.8 wt.% Cr addition could enhance the wear coefficient of a highboron HSS to around 4.82 × 10 −14 m 2 /N (Guo et al, 2022).…”