skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Improved the microstructures and properties of M3:2 high-speed steel by spray forming and niobium alloying

Abstract

The microstructures and properties of spray formed (SF) high-speed steels (HSSs) with or without niobium (Nb) addition were studied. Particular emphasis was placed on the effect of Nb on the solidification microstructures, decomposition of M{sub 2}C carbides, thermal stability and mechanical properties. The results show that spray forming can refine the cell size of eutectic carbides due to the rapid cooling effect during atomization. With Nb addition, further refinement of the eutectic carbides and primary austenite grains are obtained. Moreover, the Nb addition can accelerate the decomposition of M{sub 2}C carbides and increase the thermal stability of high-speed steel, and also can improve the hardness and bending strength with slightly decrease the impact toughness. The high-speed steel made by spray forming and Nb alloying can give a better tool performance compared with powder metallurgy M3:2 and commercial AISI M2 high-speed steels. - Highlights: • Spray forming can effectively refine the microstructure of M3:2 steel. • Niobium accelerates the decomposition of M{sub 2}C carbides. • Niobium increases the hardness and bending strength of spray formed M3:2 steel. • Spray-formed niobium-containing M3:2 steel has the best tool performance.

Authors:
 [1];  [1]; ; ; ;  [1];  [2];  [1]
  1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Xueyuan Road 30, Haidian District, Beijing 100083 (China)
  2. State Key Laboratory of Non-Ferrous Metals and Process, General Research Institute for Non-Ferrous Metals, Beijing 100088 (China)
Publication Date:
OSTI Identifier:
22587160
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 117; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMIZATION; AUSTENITE; BENDING; CARBIDES; COOLING; DECOMPOSITION; EUTECTICS; FLEXURAL STRENGTH; HARDNESS; MICROSTRUCTURE; NIOBIUM; PERFORMANCE; POWDER METALLURGY; POWDERS; SOLIDIFICATION; SPRAYS; STEELS

Citation Formats

Lu, L., Hou, L.G., E-mail: lghou@skl.ustb.edu.cn, Zhang, J.X., Wang, H.B., Cui, H., Huang, J.F., Zhang, Y.A., and Zhang, J.S.. Improved the microstructures and properties of M3:2 high-speed steel by spray forming and niobium alloying. United States: N. p., 2016. Web. doi:10.1016/J.MATCHAR.2016.04.010.
Lu, L., Hou, L.G., E-mail: lghou@skl.ustb.edu.cn, Zhang, J.X., Wang, H.B., Cui, H., Huang, J.F., Zhang, Y.A., & Zhang, J.S.. Improved the microstructures and properties of M3:2 high-speed steel by spray forming and niobium alloying. United States. doi:10.1016/J.MATCHAR.2016.04.010.
Lu, L., Hou, L.G., E-mail: lghou@skl.ustb.edu.cn, Zhang, J.X., Wang, H.B., Cui, H., Huang, J.F., Zhang, Y.A., and Zhang, J.S.. 2016. "Improved the microstructures and properties of M3:2 high-speed steel by spray forming and niobium alloying". United States. doi:10.1016/J.MATCHAR.2016.04.010.
@article{osti_22587160,
title = {Improved the microstructures and properties of M3:2 high-speed steel by spray forming and niobium alloying},
author = {Lu, L. and Hou, L.G., E-mail: lghou@skl.ustb.edu.cn and Zhang, J.X. and Wang, H.B. and Cui, H. and Huang, J.F. and Zhang, Y.A. and Zhang, J.S.},
abstractNote = {The microstructures and properties of spray formed (SF) high-speed steels (HSSs) with or without niobium (Nb) addition were studied. Particular emphasis was placed on the effect of Nb on the solidification microstructures, decomposition of M{sub 2}C carbides, thermal stability and mechanical properties. The results show that spray forming can refine the cell size of eutectic carbides due to the rapid cooling effect during atomization. With Nb addition, further refinement of the eutectic carbides and primary austenite grains are obtained. Moreover, the Nb addition can accelerate the decomposition of M{sub 2}C carbides and increase the thermal stability of high-speed steel, and also can improve the hardness and bending strength with slightly decrease the impact toughness. The high-speed steel made by spray forming and Nb alloying can give a better tool performance compared with powder metallurgy M3:2 and commercial AISI M2 high-speed steels. - Highlights: • Spray forming can effectively refine the microstructure of M3:2 steel. • Niobium accelerates the decomposition of M{sub 2}C carbides. • Niobium increases the hardness and bending strength of spray formed M3:2 steel. • Spray-formed niobium-containing M3:2 steel has the best tool performance.},
doi = {10.1016/J.MATCHAR.2016.04.010},
journal = {Materials Characterization},
number = ,
volume = 117,
place = {United States},
year = 2016,
month = 7
}
  • This paper examines the kinetics of electrode erosion and the formation and properties of the alloyed layer in a wide range of parameters of electric-spark alloying of R9K5 steel--a 1% C-9% W-4% Cr-5% Co high-speed steel--and to examine the character of vibrationless mechanized alloying with electrode materials of different classes. Alloy VK6M, a 94% WC-6% Co hard metal, and steel NTsKh45, a W-free hard steel whose exact composition is not known, were also examined for comparative and reference purposes.
  • Barium chloride salt baths are primarily used for the high-temperature quench heating of a tool formed from high-speed steels. If the barium chloride melt should have a decarbonizing effect on the surface components that are heated in it, the authors maintain that it may also affect the content of alloying elements in the surface layers of high-speed-steel components that are heated in it. Commercial salt baths with a rectifier -- chemically pure magnesium fluoride -was used for the investigation. Cooling was accomplished in a caustic melt. Analysis of the results of investigation of the molybdenum, tungsten, and cobalt distributions inmore » steel R9M4K8 as well as the tungsten and cobalt distributions in steel R9K5 indicated that the cobalt content does not diminish on heating to 1230/sup 0/C. A decrease in molybdenum content occurs in the surface layers during the quench heating of a tool formed from high-speed tungsten-molybdenum steel in a barium chloride salt bath after the required heating time, while a decrease in the tungsten content takes place with more prolonged hold times. It is shown to be possible to reduce or completely eliminate loss of alloying elements in the surface layers of a high-speedsteel tool during heat treatment when magnesium fluoride in combination with silicon carbide additives is used as a rectifier.« less
  • The solidified carbide morphology, the decomposition behavior of the M{sub 2}C carbide, and the carbide distribution after forging of an Fe-1.28C-6.4W-5.0Mo-3.1V-4.1Cr-7.9Co (wt pct) high-speed steel prepared by spray forming have been investigated. The spray-formed microstructure has been characterized as a discontinuous network of plate-shaped M{sub 2}C carbides and a uniform distribution of fine, spherical MC carbides. The metastable M{sub 2}C carbides formed during solidification have been fully decomposed into MC and M{sub 6}C carbides after sufficient annealing at high temperatures. Initially, the M{sub 6}C carbides nucleate at M{sub 2}C/austenite interfaces and proceed to grow. In the second stage, the MCmore » carbides form either inside the M{sub 6}C carbides or at the interfaces between M{sub 6}C carbides. With this increasing degree of decomposition of the M{sub 2}C carbide, the carbides become more uniformly distributed through hot forging, which produces a significant increase in ultimate bend strength. The decomposition treatment of M{sub 2}C carbide has been found to be most important for obtaining a fine homogeneous carbide distribution after hot forging.« less
  • A philosophy for the use of strong carbide formers like niobium in high speed steels is described. It follows the concept of independently optimizing the compositions of the matrix (for maximum secondary hardening potential) and the volume fraction of the blocky carbides (for protection against abrasive wear). Normally, the two are interdependent through the action of the solidification equilibria, but separate control becomes possible when the blocky carbides are formed by a strong carbide former such as niobium. During normal ingot solidification, such strong carbide formers would produce very large primary carbides. This can be avoided by atomization and powdermore » metallurgical processing. In this way, a steel has been produced whose matrix composition is similar to that of AISI M2, and whose primary carbides are all of NbC type. Its composition is 1.3C, 2W, 3Mo, 1.6V, 3.2Nb (wt pct). Because of its high stability, NbC is a much more effective obstacle to grain growth than the normal high speed steel carbides, and this allows substantially higher austenitization temperatures to be used. Despite its leaner composition, the Nb-alloyed steel matches the cutting performance of AISI M2, and its secondary hardening seems to be more persistent at high temperatures.« less
  • The authors investigated the mechanical and corrosion properties of high-chromium steel (25 wt.% Cr) particularly free of deleterious impurities (C + N < 0.02 wt.%), the so-called superferrites, additionally alloyed with 1-4% Ti or 1-2% Mo. The article shows that in principle it is possible and advantageous to alloy superferrites with titanium (1-2%). It was established that Ti and Mo reduce the corrosion rate of steel in solutions of H/sub 2/SO/sub 4/ and HCl in a broad temperature range. Steel alloyed with Mo (1-2%) or Ti (1-2%) is less prone to pitting in solution of FeCl/sub 3/ than steel 01Kh25TBmore » (the initial unalloyed one) and a number of other industrial steels. An addition of 1% Ti greatly improves the technological properties of steel 01Kh25.« less