1.4028

Definition and basic properties of martensitic steels

Martensitic steels are a group of stainless steels that can be hardened by a crystalline transformation — the transformation of austenite to martensite — achieved by rapid cooling (quenching). Their characteristic features:

• Higher carbon content compared with austenitic steels (typically 0.1–0.6% C), which enables high hardness.
• Chromium 11–18% provides basic corrosion resistance; the more chromium, the better the passive protection, but at the cost of more difficult machining and possible changes in mechanical properties.
• Quenching and tempering determine final hardness and strength; by varying heat‑treatment parameters the properties can be tailored to the application.
• Applications where hardness and wear resistance are required together with moderate corrosion resistance — knives, blades, machine parts, bearing components.

Metaphor: a martensitic steel is like a steel sword — you can harden it to make it harder, but without proper tempering it will become more brittle.

Characteristics of precipitation hardening

Precipitation hardening (PH) is a different mechanism for improving mechanical properties, operating by forming fine, dispersed precipitates of a secondary phase in the alloy matrix during controlled ageing after prior solution treatment at high temperature.

Features of PH:

• Ability to achieve high strength while retaining good ductility — an advantage over simple martensitic hardening, which often increases brittleness.
• Use of low‑temperature ageing allows gradual growth of precipitates, control of mechanical parameters and better repeatability.
• Examples of PH stainless steels: 17‑4PH (UNS S17400), 15‑5PH — widely used in aerospace, power and medical industries.
• Limitations: often require precise control of heat‑treatment and can show worse corrosion resistance in aggressive environments than the best austenitic stainless steels.

Comparison of approaches: martensitic hardening gives a rapid and significant increase in hardness via a phase change, while precipitation hardening allows a compromise between strength and ductility through controlled precipitate formation.

Comparison of mechanical properties and corrosion resistance

• Hardness and strength: martensitic steels (e.g. X30Cr13) reach higher hardness in the range 40–55 HRC after quenching; PH steels can reach comparable strengths with better ductility.
• Corrosion resistance: usually better in austenitic and some PH steels than in martensitic steels with similar chromium content; the presence of sulfur (e.g. in 420F) locally reduces corrosion resistance.
• Machinability and weldability: martensitic steels have more difficult weldability (high risk of cracking) and require careful heat treatment; PH variants may be more “friendly” in some production processes.

When selecting material one must weigh hardness and wear resistance against corrosion resistance and manufacturability. X30Cr13 (1.4028) is a good choice where priority is given to hardness and resistance to rolling/abrasive wear with moderate corrosion, whereas PH steels are chosen when a combination of strength and ductility is required.

Chemical composition and standards corresponding to the steel

The steel designated 1.4028 in the European system is X30Cr13 in alphanumeric notation. Equivalent designations encountered in comparison systems include: AISI 420 (general) and the AISI 420F variant, and the designation 3H13 (3Х13) appears in national reference systems (e.g. GOST/Russian) as a similar composition. Typical chemical composition of X30Cr13:

• C: 0.28–0.40% — the key element enabling hardening.
• Cr: 12.0–14.0% — forms a passive layer and increases corrosion resistance.
• Mn: ≤1.0%
• Si: ≤1.0%
• P: ≤0.04%
• S: ≤0.03 (in AISI 420F the S content is intentionally increased to about 0.15% for better machinability)
• Fe: balance

The difference between AISI 420 and 420F is the purposeful addition of sulfur or selenium in 420F, which improves machinability at the expense of a slight reduction in corrosion resistance and mechanical properties in areas affected by the sulfur.

Standards and reference documents:

• EN 10088 (series for stainless steels) — 1.4028 is the designation according to the EN system.
• ASTM/AISI — AISI 420/420F as commercial designations widely used in Anglo‑Saxon countries.
• GOST — equivalents such as 3Х13/3H13 in the documentation of former USSR countries.

Exact percentage ranges in normative documents may vary slightly depending on the manufacturer and intended purpose, so a certificate of conformity should be requested on purchase.

Key physical and mechanical properties

Mechanical properties depend on heat treatment; below are typical indicative values for the quenched and tempered condition:

• Hardness: after quenching and tempering 44–52 HRC (depending on carbon content and heat‑treatment parameters).
• Tensile strength: typically 700–1100 MPa in the hardened condition.
• Yield strength: 500–900 MPa (dependent on tempering temperature).
• Elongation at fracture: 8–20% (lower values at higher hardness).
• Density: approx. 7.8 g/cm3.
• Modulus of elasticity: approx. 200 GPa.

In practice these parameters translate into good wear properties and the ability to hold an edge in cutting tools, but at the cost of greater susceptibility to cracking under impact overloads or improper heat treatment.

Stages of martensitic steel production

Production of martensitic stainless steel takes place in several main stages:

1. Melting: steel is melted in electric arc furnaces (EAF) or converters, with precise control of chemical composition. Appropriate amounts of chromium, carbon and optionally sulfur (for the 420F version) are added.
2. Refining and removal of impurities: control of gas contents and impurities, neutralisation of phosphorus, sulfur and other elements.
3. Casting and rolling: pouring into ingots or continuous casting, followed by hot rolling into plates, bars or strips.
4. Homogenising anneal: removal of stresses and refinement of the structure after plastic working.
5. Finishing: cutting, grinding, and any additional surface processes.

During production control of the microstructure must be ensured to avoid excessive formation of chromium carbides at grain boundaries, which leads to reduced corrosion resistance.

Significance of precipitation‑hardening processes

Although 1.4028 is a martensitic steel, it is worth comparing the significance of PH processes:

• In PH steels, after solution treatment at high temperature, rapid cooling (quench) is followed by controlled ageing, which causes precipitation of fine particles (e.g. Cu, Ni, Al, Ti) that increase hardness and strength without a radical loss of ductility.
• Precipitation hardening requires strictly controlled times and temperatures (e.g. ageing in the range 480–620°C depending on the alloy), which allows obtaining specific mechanical properties.

For the user this means: the choice between martensite and PH depends on whether the priority is very high hardness (martensite) or a more balanced combination of hardness and ductility (PH).

Optimal annealing and hardening procedures

For X30Cr13 (1.4028) typical heat‑treatment schedules:

• Austenitising (hardening): heating to about 980–1040°C (typically around 1000°C) — holding for a short time to dissolve carbides.
• Cooling (quenching): rapid cooling, usually in oil or air (depending on the desired microstructure and requirements), to transform austenite into martensite.
• Tempering: at temperatures typically 150–200°C to retain high hardness, or higher (200–400°C) if greater ductility is required; tempering relieves excessive stresses and adjusts brittleness.
• Low‑temperature vs high‑temperature tempering: low tempering gives higher hardness at the expense of brittleness; the designer must choose a compromise.

Practical notes:

• Exact parameters depend on the specific composition and final requirements.
• Microstructure control and hardness measurements after the process are obligatory to ensure repeatability.

Wear and corrosion resistance

• Wear resistance: thanks to carbon content and the ability to achieve martensitic hardening, X30Cr13 shows good abrasive wear resistance; this makes it popular in cutting tools and components that work in contact with abrasive materials.
• Corrosion resistance: moderate — chromium (~13%) forms a passive layer, but in chloride‑containing environments the steel is more susceptible to pitting and crevice corrosion than austenitic steels (e.g. 304/316). The 420F variant with increased sulfur has somewhat reduced corrosion resistance.

Practical example: a kitchen knife made from X30Cr13 will remain relatively resistant to normal moisture, but prolonged contact with sea salt or exposure to aggressive environments will quickly degrade the surface.

Mechanical strength and ductility

• Strength: high after appropriate hardening; these materials hold an edge and cutting geometry well.
• Ductility: limited at maximum hardness; tempering is used to improve toughness and resistance to cracking.

For structures exposed to impact loads it is better to use somewhat lower hardness while retaining sufficient strength.

Drawbacks and usage challenges

• Weldability: difficult. Welding requires strict procedure and usually subsequent tempering to reduce the risk of cracking.
• Susceptibility to cracking: especially under sudden loads or improper heat treatment.
• Brittleness of the surface after machining: contaminants, excess material and local overloads can lead to crack initiation.
• Limited corrosion resistance in chloride environments.

Engineers should therefore select X30Cr13 where its strengths — hardness and wear resistance — are crucial and where corrosive conditions are moderate or can be controlled.

Tool and cutlery industry

• Knives and blades: X30Cr13 and related 420/420F are commonly used in the manufacture of kitchen knives, scissors and industrial blades due to ease of hardening and edge retention.
• Cutting dies and abrasive parts: where high surface hardness is required.

420F, thanks to sulfur, is often chosen for precision components machined in large volumes, where machinability affects production cost.

Machine parts and precision equipment

• Shafts, pins, guides: components requiring wear resistance and at the same time moderate corrosion resistance.
• Valve parts and brushes: in less aggressive environments.

Other specialised applications

• Medical equipment: in certain surgical applications, although steels with higher purity and better corrosion resistance are often preferred.
• Decorative items and metalware: where a satin finish and polishability are desired.
• Automotive parts: in places not exposed to severe corrosion but requiring hardness and strength.

Practical example: a knife manufacturer can use 420F for mass‑produced blades, taking advantage of improved machinability for lower production costs while planning finishing and user maintenance.

Corrosion mechanisms in martensitic steels

• General corrosion: occurs in acidic or oxidising conditions; chromium forms a passive layer but its continuity depends on cleanliness and microstructure.
• Localised corrosion (pitting): chlorides and other aggressors can locally disturb the passive layer, causing pitting — particularly dangerous for thin‑walled components.
• Crevice corrosion: in areas with limited access to air (welds, crevices) deactivation of the passive layer occurs faster.
• Intergranular corrosion: with improper heat treatment or precipitation of chromium carbides at grain boundaries — zones of chromium depletion can form.
• Stress corrosion cracking (SCC): although more typical for austenitic alloys in the presence of chlorides and stresses, martensitic steels with improper tempering can also suffer cracking.

Surface protection techniques

• Surface finishing: polishing and electropolishing improve the uniformity of passivation and reduce propensity for pitting.
• Chemical passivation: nitric or chromic acid baths (in accordance with standards) remove contaminants and increase the durability of the passive layer.
• Coatings: ceramic, PTFE, nickel or other protective coatings where passivation is insufficient.
• Low‑temperature nitriding/plasma nitriding: increases surface hardness with minimal impact on corrosion resistance if the process is well controlled.
• Control of the working environment: limiting exposure to chlorides, active drying, appropriate cleaning chemistry.

Importance of the working environment for material durability

The environment often defines material durability more than nominal properties. In practice:

• In a marine climate or in the presence of salt chemicals, 1.4028 will require maintenance and protection more quickly.
• In dry, moderately corrosive environments, appropriate passivation and surface maintenance are sufficient.
• In industrial processes with aggressive chemicals, consider steels with higher chromium or molybdenum content, or switch to austenitic grades (316 etc.) or PH steels depending on mechanical requirements.

For designers this means: analyse the operating environment — humidity, presence of salts, temperature and mechanical factors — before choosing 1.4028.

Cutting, grinding and polishing

• Plasma/laser cutting: possible, but parameter optimisation is required to avoid inducing excessive thermal stresses; laser cutting gives clean edges but the heat‑affected zones (HAZ) must be controlled.
• Grinding: the material grinds well, but high hardness of abrasive tools is necessary; in knife production grinding techniques determine final edge geometry.
• Polishing and surface finishing: improves corrosion resistance and aesthetics; electropolishing is particularly beneficial for removing microdefects.

Machining and finishing

• 420F: the sulfur‑containing variant is designed specifically for easy machining — lower cutting forces, longer tool life, lower production cost.
• Cutting tools: use high‑quality cemented carbides, coated tools, optimise speed and feed, and use coolant to remove heat.
• Finishing machining: use low cutting speeds and gentle parameters to avoid overheating and local stress relief.

Effect of processing parameters on material structure

• Accumulation of stresses: intensive plastic surface working can introduce residual stresses, affecting resistance to cracking.
• Local overheating: during grinding or welding zones with altered microstructure can form, affecting corrosion resistance and hardness.
• Surface contamination: burrs and contaminants negatively affect passivation; cleaning is necessary before passivation or coating.

Well‑planned machining lets you exploit the advantages of X30Cr13 while minimising hazards arising from its martensitic nature.

Differences in chemical composition and properties

• Compared with AISI 420: 1.4028 is similar; AISI 420F has added sulfur for improved machinability.
• Compared with higher‑silicon or higher‑carbon martensitics: variations in C and Cr percentages significantly affect hardness and corrosion resistance; for example alloys with higher Cr (>13%) have better corrosion resistance.
• Compared with austenitics (304, 316): austenitics have much better corrosion resistance and ductility, but are less susceptible to hardening and have lower hardness in the untreated state.
• Compared with PH (17‑4PH): PH achieves high strength with better toughness and repeatability; however the parameters of high‑temperature ageing affect its corrosion resistance.

Production costs and availability

• X30Cr13 and variants 420/420F are relatively inexpensive and widely available, making them attractive for mass production of tools and components.
• PH steels and advanced austenitics are generally more expensive, both due to composition and process requirements.

Choosing a steel for specific applications

• The choice depends on priorities: hardness and wear resistance (X30Cr13), corrosion resistance and ductility (austenitic/PH), and production costs and requirements (420F for economical machining).
• In marine environments austenitic 316 or duplex grades are recommended; in cutlery and cutting tools X30Cr13 is a common choice.

When designing a component, an engineer should always balance functional requirements with operating conditions, manufacturability and cost.

European and American material standards

• EN 10088: the basis for stainless steels in Europe; 1.4028 is listed.
• ASTM / AISI: AISI 420/420F — widely used designations in technical documentation and orders.
• GOST: equivalents such as 3Х13/3H13 in the documentation of former USSR countries.
• ISO: international standards relating to testing and completeness of material documentation.

Purchase of steel should be based on certificates provided by the manufacturer (material quality certificate confirming chemical composition and mechanical test results).

Quality control processes and material testing

• Chemical composition analysis (spectrometry): confirming contents of C, Cr, Mn, Si, P, S.
• Mechanical tests: tensile tests, hardness (HRC/HV), impact tests (Charpy) where required.
• Microstructural examinations: metallography, determination of amount and distribution of carbides, thickness of HAZ.
• Corrosion tests: e.g. salt spray tests or pitting potential in electrochemical tests.
• Non‑destructive testing: ultrasonic, penetrant, radiography for critical elements.

For parts of infrastructure or medical importance, certificates conforming to industry standards and periodic testing are required.

Modern production and processing technologies

• Powder technologies and powder metallurgy (PM): allow uniform microstructure and unique properties, e.g. fine carbide dispersions.
• Additive manufacturing (3D printing): being developed for martensitic stainless alloys as well; specific post‑printing heat‑treatment strategies are required.
• Advanced coatings and hybrid surface treatments: combining plasma nitriding with thin ceramic coatings to maximise wear and corrosion resistance.

Environmental challenges and material durability

• Sustainability: steel recycling and reduction of critical element consumption are becoming priorities; steels with lower nickel and other expensive additions gain importance.
• Limitations of chemical processes: passivation and coatings must become more environmentally friendly, which influences selection of finishing processes.

Potential new application areas

• Advanced tools in renewable energy: small turbine blades, guides, fastening elements.
• Medical applications: where a combination of hardness and biocompatibility is required — this, however, needs further research and certification.
• Precision industry: machined parts with complex geometries in mass production benefiting from 420F.

Technological progress opens opportunities to adapt martensitic and PH steels to new requirements, especially when combined with modern processing techniques.

Selecting steel for specific working conditions

• Choose 1.4028 when priorities are: hardness, wear resistance, ease of hardening and moderate corrosion resistance.
• Use 420F where high machinability and optimisation of mass‑production costs are important.
• In aggressive chemical environments prefer alloys with higher chromium, molybdenum or austenitic grades, or PH steels depending on strength requirements.

Recommendations for maintenance and operation

• Regular washing and drying of parts, especially those exposed to salts and chlorides.
• Passivation and/or electropolishing of surfaces after machining or assembly.
• Monitor surface condition and promptly remove localised corrosion sites.
• For welded repairs, use appropriate welding procedures and temper joints afterwards.

Avoiding common mistakes and damage

• Do not apply sudden cooling without planned heat treatment — risk of cracking.
• Do not ignore the effect of sulphur addition in 420F on corrosion resistance — appropriate surface protection is necessary.
• Avoid welded joints where the design requires high mechanical integrity; if welding is necessary, plan heat treatment after the process.
• Pay attention to microstructure control and hardness measurements after heat treatment — deviations from specification are a source of defects.

Using 1.4028/X30Cr13 or 420F requires awareness of their limitations and an appropriate design process. With the right material selection, production control and correct service, this steel offers a favourable balance of hardness, strength and production cost.