Effects of Tempering Temperature on Wear Resistance and Surface Roughness of a High Speed Steel Roll.

Abstract

The effects of tempering temperature on wear resistance and surface roughness of a high speed steel (HSS) roll manufactured by centrifugal casting method were investigated in this study. Hot-rolling simulation test was carried out using a high-temperature wear tester capable of controlling speed, load, and temperature. The test results revealed that the peak-tempered roll specimen showed the best wear resistance because of its hard matrix. However, its surface roughness deteriorated as the scratching wear proceeded, thereby leading to increase in friction coefficient. In the over-tempered specimens containing numerous fine spherical carbides in the matrix, the abrasive wear occurred predominantly as fine carbides were fallen off from the matrix, and thus the surface roughness was enhanced by the homogeneous wear of both matrix and carbides. These findings suggested that the tempering treatment at temperatures slightly past the peak hardness point would be more desirable in order to improve the wear resistance with consideration of the surface roughness of the HSS roll.

The Transformation of Carbides during Austenization and Its Effect on the Wear Resistance of High Speed Steel Rolls

“…These fine carbides can become detached from the matrix in the initial wear stage, and then act as wear debris at the interface between the loading material and the matrix, causing abrasive wear to occur, as previously reported. [16] This is verified by the observation of a large number of fine spherical carbide particles on the wear surface ( Figure 4) and may also be the reason for the very similar values of the friction coefficient (approximately 0.8) during wear testing of specimens A through C.…”

“…These include the hard carbides formed along cell boundaries or inside cells, the tempered martensite matrix, and the fine spherical carbides precipitated in the matrix. [16] Due to the high hardness of the coarse carbides, the overall bulk hardness, wear properties, and surface roughness can be directly affected by the type, shape, volume fraction, and distribution of these carbides. [6,7,8] The matrix, however, governs the overall bulk hardness and provides both strength and fracture toughness.…”

Effect of solidification rate on the morphology and distribution of eutectic carbides in centrifugal casting high-speed steel rolls

“…(3) The heat treatment method. This technique has been demonstrated by Lee et al (2001) and Wang (2003). Lee et al (2001) obtained fine carbides in the matrix via temper hardening.…”

The Effect of Long-Time Austenization on the Wear Resistance and Thermal Fatigue Properties of a High-Speed Steel Roll

“…These microhardness values are close to those reported elsewhere. [7] The compositions (wt pct) of the carbides were determined as C-70.6Fe-0.2W-3.69Mo-9.78Cr-3.06V (M 3 C), C-7.16Fe-16.45W-26.49Mo-23.35Cr-13.51V (M 2 C), and C-2.6Fe-10.84W-5.87Mo-4.69Cr-60.28V (MC). Figure 4 shows the average distance between neighboring carbides as a function of austenizing time.…”

“…These include the hard carbides formed along cell boundaries or inside cells, the tempered martensite matrix, and the fine spherical carbides precipitated in the matrix. [7] In order to improve wear resistance, it is desirable to form carbides of high hardness discontinuously and homogeneously inside cells or along cell boundaries and to raise the overall bulk hardness by increasing the matrix hardness. [8] If the carbides are bulky and are located mainly at cell boundaries, the average distance between neighboring carbides is large and the matrix, therefore, will be preferentially worn.…”