What is Carbide?

Description

Carbides are hard crystalline compounds formed when carbon bonds with metals like chromium, vanadium, or tungsten during steel heat treatment. They provide wear resistance and edge retention in scissor blades but must be properly distributed to avoid micro-chipping.

What is Carbide?

Carbides are hard crystalline compounds formed when carbon bonds with metals like chromium, vanadium, or tungsten during steel heat treatment. In scissor steels, these particles are embedded throughout the steel matrix and act as hard points that resist abrasion and maintain the cutting edge over time.

Why It Matters for Scissors

Carbide volume and distribution directly determine how long a scissor blade holds its edge between sharpenings. VG-10 contains approximately 12-16% carbide volume according to Knife Steel Nerds research, primarily chromium-rich M23C6 type carbides. These carbides are harder than the surrounding martensite matrix — typically 1,200-1,800 HV compared to the matrix at around 700-800 HV.

However, carbides are a double-edged factor. Large, blocky carbides (common in conventionally melted high-carbon steels) can fracture out of the edge during cutting, leaving micro-chips that feel rough and reduce cutting precision. This is why powder metallurgy steels like SG2 and Cowry-X are prized — they produce extremely fine, uniformly distributed carbides that support the edge without creating weak points. For scissors specifically, where two blades contact each other with every cut, carbide size and distribution are even more critical than in single-blade knives.

Technical Detail
Carbide formation in scissor steels is governed by the alloying elements present and the heat treatment parameters used. The major carbide types found in common scissor steels include: - **M23C6 (Chromium-rich):** The dominant carbide in VG-10 and GIN-series steels. Forms during solidification and tempering. Chromium content of 12-15% in these steels promotes abundant M23C6 formation. - **MC (Vanadium-rich):** Found in steels with vanadium additions like VG-10W. These are among the hardest carbides (~2,800 HV) and are extremely effective for wear resistance. - **M7C3 (Mixed chromium):** Can form in higher-carbon steels like ZDP-189 (3% carbon). These are harder than M23C6 but less thermally stable. The austenitizing temperature during heat treatment controls how many carbides dissolve back into the matrix versus how many remain as undissolved particles. A higher austenitizing temperature dissolves more carbides, putting more carbon and chromium into solution — this increases hardness after quenching but reduces the number of hard particles available for wear resistance. Conversely, lower austenitizing temperatures leave more undissolved carbides, which aid wear resistance but reduce the carbon available in the martensite matrix, lowering achievable HRC. Steel manufacturers publish optimal austenitizing temperatures that balance these competing factors. In powder metallurgy steels, the rapid solidification of atomized powder particles produces much finer carbides (often under 3 microns) compared to conventionally cast steels where carbides can reach 10-30 microns. This is the fundamental advantage of PM steels for precision cutting tools.

Sources

Frequently Asked Questions

The most common are chromium-rich carbides (M23C6) in steels like VG-10, and vanadium-rich carbides (MC type) in higher-alloy steels like VG-10W. The type depends on which alloying elements are present.

Both. Carbides increase edge retention and wear resistance, but large or clustered carbides can cause micro-chipping at the cutting edge. The goal is many small, evenly distributed carbides rather than fewer large ones.

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