What does this research mean for the field?

In AISI-D3 tool steel, adding refining elements above 0.06 wt.%, applying solutionizing heat treatment, and increasing the cooling rate refines primary M₇C₃ carbides and improves the balance between hardness and toughness. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

The research aims to analyze how rare earth additives and heat treatment affect primary M₇C₃ carbides in AISI-D3 tool steel.

May 20, 2026Open Access

Refining of Primary M₇C₃ Eutectic Carbides in AISI-D3 Tool Steel

Key Points

The research aims to analyze how rare earth additives and heat treatment affect primary M₇C₃ carbides in AISI-D3 tool steel.
Examined carbide morphology, size, and distribution using optical microscopy and scanning electron microscopy.
Conducted evaluations on samples with varying rare earth content and different cooling rates.
Measured mechanical properties to determine the effects of cooling rate on hardness and toughness.
Higher rare earth additions resulted in refined carbide morphology and better distribution.
Increased cooling rates decreased carbide volume fraction and eutectic cell size.
A high cooling rate produced better mechanical properties, balancing hardness and toughness.

Abstract

In the present study, the morphology, size and distribution of primary M₇C₃ carbide in AISI-D3 tool steel has been considered as a function of rare earth’s addition, solutionizing heat treatment and solidification rate. The optical microscopy images were quantitatively evaluated by Image tool software and scanning electron microscopy equipped with X-ray energy dispersive spectrum was implemented to scrutinize the carbide morphologies and their chemical compositions. The obtained results showed that addition of refining elements under 0.06 wt.% had no pronounced influence on carbide refining while the higher content additions induced the different dominating morphology of carbides in microstructure and refined the coarse carbides. More homogeneous distribution of primary carbides found in heat treated samples. The carbide volume fraction, eutectic cell size and secondary dendrite arm spacing of austenite are also decreased as the cooling rate increased. Mechanical properties surveys released that in comparison with other practices, a high cooling rate could produce a steel with better balance between hardness and toughness properties.

Refining of Primary M₇C₃ Eutectic Carbides in AISI-D3 Tool Steel

Key Points

Abstract

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