Prepare the matrix
Use the grade-specific hardening range and soak to place the intended carbon and alloying elements into austenite
Kizlyar Supreme metallurgy guide
Cryogenic treatment
What controlled cooling below room temperature can change in hardened knife steel—and why the answer depends on the alloy and the complete cycle
Evidence reviewed 10 September 2026 · Sources and limits stated below
The short version
Not magic and not a substitute for hardening
Cryogenic treatment is a supplemental step inside a steel-specific heat-treatment route. After quenching, some steels retain austenite that has not transformed to martensite. Controlled cooling below room temperature can transform more of it; the following temper then treats the newly formed martensite and develops the final structure.
SupplementalIt supports a correct hardening route rather than rescuing an unsuitable one
Alloy-dependentThe response changes with chemistry, prior heat treatment and target properties
Temper followsThe cycle must end with tempering so new martensite is not left untempered
MeasuredRetained austenite, hardness, wear and toughness matter more than the word “Cryo”
Why cold can matter
Room temperature is not always the end of the quench
When austenitized steel is cooled rapidly, much of its high-temperature austenite transforms to hard martensite. The transformation begins at a steel-specific Ms temperature and progresses as temperature falls. In high-carbon and high-alloy steels, the finish temperature may lie below room temperature, so part of the austenite remains.[1]
That retained austenite is not automatically a defect. A controlled amount can contribute toughness, while too much can lower hardness or reduce dimensional stability. The desired amount depends on the alloy, edge geometry, tempering route and use. The objective is a controlled balance—not simply “zero austenite.”
Cooling below room temperature extends the transformation opportunity. Research also reports changes in martensitic defect structure and fine-carbide precipitation during subsequent tempering, but these effects vary by material and cycle and are not equally visible in every steel.[4][5]
Kizlyar Supreme expanded cryogenic processing beyond powder steels to selected conventionally produced tool and stainless grades
The process position
Quench, controlled cold, then temper
Terminology varies across industry. “Sub-zero,” “cold treatment,” “deep freezing” and “deep cryogenic treatment” may describe different temperature bands. The meaningful specification is the full time-temperature route and the measured result.
Form martensite
Cool fast and uniformly enough to obtain the intended structure while managing distortion and crack risk
Reduce retained austenite
Where the validated route calls for it, continue cooling to a controlled sub-zero or cryogenic level
Stabilise the result
Temper according to the steel-specific route; additional tempers may be required for high-alloy steels
Why the final temper is essential
Martensite formed during the cold step is newly formed and untempered. Uddeholm therefore states that the final operation must be tempering when sub-zero treatment is used for high dimensional stability.[1] A blade should never be treated as finished simply because it has returned from the cryogenic stage.
Benefits and limits
Useful when the metallurgy gives it something to change
A credible claim starts with “can,” not “always.” Published results depend on austenitizing, quench, cold temperature, cooling rate, hold time, sequence, tempering and the measurement used.
Dimensional stability
Reducing retained austenite can reduce later transformation in service. This is why steelmakers emphasise sub-zero treatment for parts with demanding stability requirements.[1]
Hardness and wear
Suitable routes can increase hardness or wear resistance through additional martensite and changes developed during tempering. Uddeholm reports up to 1–2 HRC in some low-temperature-temper routes, but little or no increase in some high-temperature-temper routes
Toughness and corrosion
These responses are not universally positive. Alleima notes a slight toughness reduction for its deep-freezing guidance, while modern reviews report steel- and sequence-dependent corrosion behaviour.[3][5]
One experiment is not every knife
A 2022 M390/M398 study compared samples with and without a −78 °C step and found that the size of the hardness and wear response changed with steel and tempering temperature.[7] Its ball-on-disc test is valuable metallurgy evidence, but it is not a direct percentage promise for knife-edge life.
Kizlyar Supreme development
Expanding cryogenic treatment step by step
The programme began with powder steels and expanded as Kizlyar Supreme developed and validated steel-specific routes for a broader range of tool and stainless grades. The chronology below records that production development; the marking guide explains how to identify a treated knife.
Powder steels
The programme began with highly alloyed powder-metallurgy steels, where retained-austenite control and demanding property targets justified the additional operation
PGK, Sleipner and N690
Experience and process control then supported steel-specific cryogenic routes for selected production in these tool and stainless grades
AUS-10Co, VG-10 and selected AUS-8 batches
Cryogenic treatment has now expanded to more AUS-10Co and VG-10 production and, where the defined batch route calls for it, selected AUS-8 batches
How to identify it
Look for the Cryo designation on the knife
Knives that have received cryogenic treatment are normally identified by the word Cryo, a snowflake symbol or another model- or batch-specific designation confirming the process.
“Cryo” on the bladeA direct written designation may appear beside the steel or model marking.
Snowflake symbolA snowflake is another clear visual confirmation used on treated production.
Other confirmed designationSome model or batch documentation can identify the treatment in another explicit way.
Before
2025
2025
Earlier markings were not applied uniformlyNot every pre-2025 Kizlyar Supreme knife that received cryogenic treatment was marked. The designation appeared mainly on powder-steel knives, although the process had also been implemented for other qualifying production. When identification matters, confirm the exact model and batch with Kizlyar Supreme.
Cryogenic treatment is one part of the steel-specific route; geometry, grinding control, finishing and final inspection still determine the complete blade
What “Cryo” does not mean
Four myths worth leaving behind
It does not align molecules. The evidence concerns phase transformation, martensitic structure, defects and carbide precipitation—not a mystical rearrangement.
It is not automatically liquid nitrogen. Sub-zero treatments use different target temperatures and equipment. The stated cycle matters more than the label.
It does not always improve every property. A gain in hardness or wear resistance may coincide with little change—or a trade-off—in toughness or corrosion response.
It cannot rescue an incorrect preceding cycle. Austenitizing, quenching, timing and tempering remain fundamental. Cryogenic treatment works only as part of the whole route.
Cryogenic-treatment FAQ
Clear answers about cold-treated knife steel
What does cryogenic treatment do to knife steel?
It can transform part of the retained austenite left after quenching and alter the subsequent development of martensite and fine carbides during tempering. The magnitude depends on steel and cycle.
Does every knife steel benefit from cryogenic treatment?
No. It is most relevant when the chosen hardening route leaves retained austenite or when testing shows a useful improvement. Some steels and tempering routes show little benefit.
Does cryogenic treatment always make a blade harder?
No. Uddeholm reports up to 1–2 HRC in some low-temperature-temper routes, but little or no increase in some high-temperature-temper routes. Other properties may change independently of HRC.
Does cryogenic treatment improve toughness?
Not automatically. The response varies; transforming soft retained austenite can reduce one source of toughness even while stability or wear resistance improves. The complete balance must be tested.
Must a cryogenically treated blade be tempered?
Yes. Newly formed martensite must not be left untempered. The steel-specific route should finish with the prescribed tempering cycle.
Which Kizlyar Supreme knives receive cryogenic treatment, and how can I identify them?
Kizlyar Supreme began with powder steels, expanded to PGK, Sleipner and N690, and now uses cryogenic treatment more broadly with AUS-10Co and VG-10 and in selected AUS-8 batches. A treated knife is normally identified by “Cryo,” a snowflake or another confirming designation. Not every pre-2025 treated knife was marked; if identification matters, confirm the exact model and batch with Kizlyar Supreme.
Sources and further reading
Evidence behind this guide
- Uddeholm, Heat Treatment of Tool Steel — retained austenite, common sub-zero temperatures, hardness limits and the requirement to finish with tempering
- Uddeholm, Sleipner data sheet — a grade-specific example of sub-zero treatment and retained-austenite response
- Alleima, Deep-freezing of knife steel — knife-specific purpose, temperature ranges and hardness/toughness trade-off
- Chowwanonthapunya, Peeratatsuwan and Rithinyo, Cryogenic treatment of tool steels: a brief review and a case report, Maritime Technology and Research 4(1), 2022
- Jurči et al., Cryogenic Treatment of Martensitic Steels, Materials 17(3), 548, 2024 — comprehensive review of mechanisms, sequences and property variability
- Das, Dutta and Ray, Optimization of the duration of cryogenic processing to maximize wear resistance of AISI D2 steel, Cryogenics 49(5), 2009
- Studený et al., Analysis of Tribological Properties of Powdered Tool Steels M390 and M398 in Contact with Al2O3, Materials 15(21), 7562, 2022
- Kizlyar Supreme, Knife Manufacturing in Russia — official factory description of steel-specific heat treatment and selected cryogenic processing
- Kizlyar Supreme, refining steel-specific heat treatment with Sergey Burov — official factory discussion
Specialist contribution: We thank Dmitry Schneider, Technical Consultant at High Performance Metals Company Limited (ООО «ВЭМ»)—one of Kizlyar Supreme’s suppliers of high-performance steels—for his contribution and specialist expertise. This guide draws on technical articles supplied by ООО «ВЭМ» and adapted with permission; public metallurgical claims were independently checked against the sources listed above. The Kizlyar Supreme adoption sequence and pre-2025 marking history are company-confirmed manufacturing statements.
Look beyond the word “Cryo”
Choose a knife by its complete design and intended use, then use the exact model specification to understand the steel and processing behind it.