Abstract
The microstructure and carbides evolution of high-speed steel after electroslag remelting and solution treatment were studied. The thermodynamic precipitation mechanism of carbides in solid phase was discussed and the characteristic parameters of carbides in different processes were also investigated. The results show that there were large lamellar and fibrous Mo2C and a small amount of VC in the ESR ingot. Mo2C are metastable carbides, which can be decomposed into VC and Fe2Mo4C during the solution treatment. The average diameter of the carbides is reduced to 1.28 μm and the space distance is reduced to 3.23 μm after forging and hot rolling, which means carbides are completely spheroidal and dispersed in matrix.
Highlights
High-speed steels (HSS) are widely used in making high-speed cutting tools, which always require high hardness, good wear resistance, and good thermal fatigue resistance at elevated temperatures [1,2]
It is well known that the type, morphology, size, and distribution of carbides have great influence on the mechanical properties of high-speed steel, which are closely related to the as-cast structure of ingots, especially eutectic carbides
It has been reported that the presence in carbide distribution of significant fraction of ultrafine particles can improve wear resistance of high-speed steel by 2.13 times compared with the conventional treatment while hardness increases by 7.76% and wear rate decreases [9,10,11]
Summary
High-speed steels (HSS) are widely used in making high-speed cutting tools, which always require high hardness, good wear resistance, and good thermal fatigue resistance at elevated temperatures [1,2] This kind of wear-resistant and heat-resistant tool steel with secondary hardening characteristics contains a large amount of tungsten, molybdenum, vanadium, chromium, and other alloy elements [3,4,5]. The alloying elements are easy to segregate seriously and form large eutectic carbides in the manufacturing process, which is difficult to eliminate in the subsequent forging and other heat treatment processes [16]. The present work aims to study the effect of heat treatment and hot deformation on morphology, size, and distribution of carbides in high speed steel after ESR-CDS process. Thick eutectic carbide can be eliminated, and carbide shape and product performance can be eventually improved
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