Difference Analysis between Carburizing and Nitriding of Stainless Steel

1. Process Principle and Objective

Carburizing is to infiltrate carbon (C) and nitrogen (N) into the surface of stainless steel at high temperature (900–950°C) to form carbides (such as Fe₃C) and nitrides (such as CrN, Fe₄N) to improve surface hardness, wear resistance and compressive strength.

Features: High temperature is required to activate diffusion, but the high Cr/Ni content of stainless steel may hinder the diffusion of carbon, and the process parameters (such as the type of infiltrant and the holding time) need to be optimized.

Nitriding is to infiltrate nitrogen into the surface of stainless steel at medium and low temperatures (500–600°C) to generate nitrides (such as Cr₂N, Fe₄N) and form a dense hardened layer.

Features: Low temperature, little effect on the matrix structure, and strong affinity between nitrogen and Cr, making it easier to form a uniform nitride layer on the surface of stainless steel.

2. Process parameters and applicability
Carbonitriding
Temperature range 900–950°C (protective atmosphere required)
Processing time 1–4 hours (high temperature accelerates diffusion)
Deepness of hardened layer 0.1–0.3 mm (carbon diffusion is limited)
Corrosion resistance May be reduced (risk of carbide precipitation)

Nitriding
Temperature range 500–600°C (vacuum or gas possible)
Processing time 4–12 hours (low temperature requires longer)
Deepness of hardened layer 0.05–0.15 mm (uniform nitrogen diffusion)
Corrosion resistance Improved (nitride film is dense)

3. Comparison of modification effects

Hardness and wear resistance
Carbonitriding: The surface hardness can reach HRC 60–65, but the Cr/Ni of stainless steel hinders carbon diffusion, and the actual effect is weaker than that of ordinary steel.

Nitriding: Hardness HRC 55–60, more uniform nitride film, excellent wear resistance, and less effect on corrosion resistance.

Corrosion resistance
Carbonitriding: Carburizing may cause intergranular corrosion (Cr depletion), which requires subsequent treatment (such as solution treatment).
Nitriding: The nitride film (CrN) itself is corrosion-resistant, and the nitride of Cr can enhance the surface passivation ability.

4. Application scenarios

Carbonitriding: Suitable for stainless steel parts that require high wear resistance and pressure resistance (such as gears and bearings), but the loss of corrosion resistance needs to be weighed.
Nitriding: Suitable for medical equipment, chemical equipment and other scenarios that require both corrosion resistance and surface strengthening (such as surgical instruments, pump and valve parts).
5. Process limitations and challenges
Carbonitriding: High temperature can easily lead to coarsening of stainless steel grains, and the cooling rate needs to be strictly controlled.
Carbon infiltration may reduce corrosion resistance and require subsequent passivation treatment.
Nitriding: The low-temperature process takes a long time and the production efficiency is low. The nitride layer is thin, and the demand for deep strengthening is limited.
Summary
The core difference between stainless steel carbonitriding and nitriding lies in the infiltration elements, temperature sensitivity and modification effect. Carbonitriding pursues high strength but sacrifices some corrosion resistance, while nitriding achieves surface strengthening while maintaining corrosion resistance. The selection should be based on a comprehensive assessment of the specific working conditions (such as wear environment, corrosive media) and process feasibility (cost, time).