What is the difference between 9Cr18 and 440C stainless steel materials?

Both 9Cr18 and 440C stainless steel are high-carbon martensitic grades known for their excellent hardness, wear resistance, and ability to maintain sharp edges - making them popular choices for knives, bearings, valves, and precision instruments. However, while they share similar properties, there are important differences in composition, mechanical performance, corrosion resistance, and applications that influence material selection.

 

What is 9Cr18 Stainless Steel Materials?
9Cr18 is a high-carbon, high-chromium martensitic stainless steel known for its hardness, wear resistance, and corrosion resistance after heat treatment. It is used in applications that require high performance, such as cutting tools, surgical blades, bearing parts, and wear-resistant components for pumps and valves.

 

What is 440C Stainless Steel Materials?
440C stainless steel is a high-carbon, martensitic stainless steel known for achieving the highest strength, hardness, and wear resistance among the 440 series after heat treatment. It is a magnetic material with moderate corrosion resistance, suitable for applications like high-quality knife blades, surgical instruments, and rolling element bearings.

 

What is the difference between 9Cr18 and 440C stainless steel materials?

Both 9Cr18 and 440C are martensitic stainless steels, both highly hard and resistant to low dynamic loads. They exhibit high hardness and wear resistance after quenching, reaching HRC60° or higher after heat treatment. 9Cr18 is a high-carbon, high-chromium martensitic stainless steel suitable for the manufacture of automatic control valve components requiring high wear resistance, high loads, and non-corrosive media. 9Cr18 readily oxidizes in contact with water, so its use should be avoided in areas where it is exposed to water or steam. 440C is a martensitic stainless steel primarily used in the manufacture of bearings and valve seats for use in low-corrosion environments, non-lubricated, and highly oxidizing atmospheres. 440C exhibits excellent high-temperature dimensional stability.

Chemical Composition

Element	9Cr18 (GB/T 1220)	440C (AISI/ASTM A276)
C (Carbon)	0.85–0.95%	0.95–1.20%
Cr (Chromium)	17.0–19.0%	16.0–18.0%
Mn (Manganese)	≤1.0%	≤1.0%
Si (Silicon)	≤1.0%	≤1.0%
Ni (Nickel)	≤0.6%	≤0.75%
Mo (Molybdenum)	≤0.75%	≤0.75%
P + S	≤0.03%	≤0.03%

 

Mechanical Properties

Property	9Cr18	440C
Tensile Strength (MPa)	760–980	800–1000
Yield Strength (MPa)	≥ 520	≥ 550
Hardness (HRC)	56–60	58–62
Elongation (%)	≥ 20	≥ 18
Density (g/cm³)	7.75	7.74

Summary:
440C stainless steel achieves slightly higher hardness and tensile strength after proper heat treatment, while 9Cr18 offers better toughness and corrosion performance in humid or slightly acidic environments.

 

Corrosion Resistance
9Cr18 stainless steel performs better in wet or mildly corrosive environments due to its higher chromium content and refined microstructure after proper tempering.440C stainless steel has excellent corrosion resistance but is more prone to pitting when exposed to chlorides or acidic conditions if not polished or passivated properly.

 

Applications

9Cr18 Stainless Steel	440C Stainless Steel
Surgical instruments	High-end knife blades
Bearings and valves	Ball bearings and races
Food processing equipment	Measuring tools
Industrial blades	Aerospace components

Both materials are commonly used in knife manufacturing, but 440C is generally used in premium blades or cutting tools requiring a harder edge.

 

Price and Availability

9Cr18 stainless steel plate price per kg: around US $2.8–$3.2/kg depending on thickness and surface finish.
440C stainless steel plate price per kg: around US $3.5–$4.0/kg for high-quality polished or precision ground plates.

 

GNEE offers both 9Cr18 and 440C stainless steel plates, sheets, and bars with thicknesses ranging from 2mm to 60mm, available in annealed, hardened, or precision-ground conditions. Custom cutting, heat treatment, and surface polishing services are also available to meet exact project specifications.Email: info@gneestainless.com