Carbides in high-speed steels containing silicon

Abstract

The effects of silicon additions up to 3.5 wt pct on the as-cast carbides, as-quenched carbides, and as-tempered carbides of high-speed steels W3Mo2Cr4V, W6Mo5Cr4V2, and W9Mo3Cr4V were investigated. In order to further understand these effects, a Fe-16Mo-0.9C alloy was also studied. The results show that a critical content of silicon exists for the effects of silicon on the types and amount of eutectic carbides in the high-speed steels, which is about 3, 2, and 1 wt pct for W3Mo2Cr4V, W6Mo5Cr4V2, and W9Mo3Cr4V, respectively. When the silicon content exceeds the critical value, the M 2 C eutectic carbide almost disappears in the tested high-speed steels. Silicon additions were found to raise the precipitate temperature of primary MC carbide in the melt of high-speed steels that contained d-ferrite, and hence increased the size of primary MC carbide. The precipitate temperature of primary MC carbide in the high-speed steels without d-ferrite, however, was almost not affected by the addition of silicon. It is found that silicon additions increase the amount of undissolved M 6 C carbide very obviously. The higher the tungsten content in the high-speed steels, the more apparent is the effect of silicon additions on the undissolved M 6 C carbides. The amount of MC and M 2 C temper precipitates is decreased in the W6Mo5Cr4V and W9Mo3Cr4V steels by the addition of silicon, but in the W3Mo2Cr4V steel, it rises to about 2.3 wt pct.

Study of the Origin of the Unexpected Pearlite during the Cooling Stage of Two Cast High-Speed Steels

“…6b) gives an overview of the elements distribution within the studied phases on HSS grade B. Both morphology and average chemical compositions of carbides found in HSS grades A and B seem to be in good agreement with the results given in previous studies [1][2][3][4][5][6][7][8][9][11][12][13][14][15]. …”

Effects of Silicon on the Microstructure and Mechanical Properties of 15–15Ti Stainless Steel

“…Bartlett et al [16] once performed first-principles calculations and claimed that the Si-C interaction was repulsive. Pan et al [17] reported that silicon additions could increase the carbon activity in melt and elevate the primary precipitation temperature of MC carbide, thereby raising the size of primary MC carbides. Moreover, Ubhi and Baker [18] stated that the effect of silicon was merely accelerating the formation of MC carbides, and it had little influence on the volume fraction of precipitates.…”

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

“…At present, the role of Si in high-speed steel has attracted more attention. Pan et al, found that with the increase of Si, the content of M 2 C carbides in the microstructures of the steels decreased sharply, and the amount of M 6 C carbides increased rapidly [ 26 ]. The addition of only small quantities of Si can alter the microstructure and carbide types in steels, leading to significant enhancement in the mechanical properties of the material [ 27 ].…”