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The solidified carbide morphology, the decomposition behavior of the M 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 2 C carbides and a uniform distribution of fine, spherical MC carbides. The metastable M 2 C carbides formed during solidification have been fully decomposed into MC and M 6 C carbides after sufficient annealing at high temperatures. Initially, the M 6 C carbides nucleate at M 2 C/austenite interfaces and proceed to grow. In the second stage, the MC carbides form either inside the M 6 C carbides or at the interfaces between M 6 C carbides. With this increasing degree of decomposition of the M 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 2 C carbide has been found to be most important for obtaining a fine homogeneous carbide distribution after hot forging.

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