Abstract
In this paper, the precipitation of carbide and wear loss of high-carbon 8 mass% Cr tool steel at two tempering conditions (i.e., 773–803 K and 823–853 K) were studied by INCA Steel, EPMA-1720H, XRD, and ML-10 tester. The results show that the particles of test steels include the carbides (Cr7C3 and Cr23C6) and carbides nucleated on Al2O3. When carbides are of the same size, the number of carbides in test steel at a tempering temperature of 773–803 K is greater than that at a tempering temperature of 823–853 K, especially when the size of carbides is less than 5 μm. Compared with the test steel tempered at 823–853 K, the distance between adjacent actual particles reduced by 80.6 μm and the maximum amount of reduction was 9.4% for single wear loss at the tempering temperature of 773–803 K. It can be concluded from thermodynamics results that Al2O3 inclusions began to precipitate in liquid, and the precipitation of carbides was at the solid–liquid region. Al2O3 can be used as the nucleation interface of carbide, thus promoting the formation of carbides. During the cooling of molten steel, a lower temperature can increase the difference of actual solubility product bigger than equilibrium solubility product, thus promoting the carbide formation.
Highlights
In recent years, cutting dies, forming dies, gauges, and other tool steel have attracted attention in the critical applications of cold-worked tool steels [1]
For the steel material matrix, studies showed that the distribution of carbides played an important role in improving wear resistance [4,5,6]
In the electroslag remelting–continuous rapid solidification (ESR-CRS) process, increasing water-cooling pressure is beneficial to reducing the formation of primary carbides
Summary
In recent years, cutting dies, forming dies, gauges, and other tool steel have attracted attention in the critical applications of cold-worked tool steels [1]. The methods for improving wear resistance include producing a metal matrix composite (MMC) by spraying carbide on a metal surface, and inlaying a hard alloy outside the steel matrix [2,3]. These costs are much higher than ordinary steel materials. In the electroslag remelting–continuous rapid solidification (ESR-CRS) process, increasing water-cooling pressure is beneficial to reducing the formation of primary carbides. The precipitation of primary carbide and grain boundary cementite can be effectively inhibited by controlling the water cooling pressure above 0.06 MPa. Due to the nonequilibrium segregation behavior, temperature affects the total boron concentration of Materials 2018, 11, 2491; doi:10.3390/ma11122491 www.mdpi.com/journal/materials
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