Carburizing vs nitriding

Carburizing and nitriding are both important surface hardening processes in metallurgy, with the following differences:
Process Principles

• Carburizing: It involves heating low-carbon steel or low-carbon alloy steel in a carbon-rich medium at a certain temperature. The carbon source decomposes to produce active carbon atoms, which are absorbed by the steel surface and diffuse inward, increasing the carbon content of the steel surface.
• Nitriding: It is the process of allowing active nitrogen atoms to penetrate the surface of steel at a certain temperature, forming a nitride layer. Nitrogen atoms react with alloying elements in the steel to create nitrides with high hardness and good wear resistance.
Process Temperature and Time

• Carburizing: The temperature is generally between 850°C and 950°C. The process takes a relatively long time, usually several to dozens of hours, depending on the required depth of the carburized layer.
• Nitriding: The temperature is relatively low, typically between 500°C and 600°C. The time is also long but shorter than that of carburizing, usually dozens to hundreds of hours.
Properties of the Penetrated Layer

• Hardness and Wear Resistance

• Carburizing: The surface hardness of the steel can reach 58-64 HRC after carburizing, showing high hardness and wear resistance.
• Nitriding: The surface hardness of the steel can reach 1000-1200 HV after nitriding, which is higher than that of carburizing, with better wear resistance.
• Fatigue Strength

• Carburizing: It can improve the fatigue strength of steel, especially in bending and torsional fatigue.
• Nitriding: It can also enhance the fatigue strength of steel, but the effect is relatively weaker than that of carburizing.
• Corrosion Resistance

• Carburizing: The corrosion resistance after carburizing is relatively poor.
• Nitriding: A dense nitride layer is formed on the steel surface after nitriding, which provides better corrosion resistance.
Applicable Materials

• Carburizing: It is suitable for low-carbon steel and low-carbon alloy steel, and is often used in the manufacturing of gears, shafts and other parts that bear large loads and friction.
• Nitriding: It is suitable for steels containing alloying elements such as aluminum, chromium and molybdenum. It is often used to manufacture high-precision and high-wear-resistant parts, such as molds and measuring tools.
Process Characteristics

• Carburizing

• Advantages: It can obtain a relatively deep carburized layer, improving the load-bearing capacity of parts. The process is relatively simple and the cost is low.
• Disadvantages: The carburizing temperature is high, which can easily cause part deformation. Heat treatment such as quenching is required after carburizing, increasing the process complexity.
• Nitriding

• : The nitriding temperature is low, resulting in less part deformation. It can achieve high hardness, good wear resistance and corrosion resistance. There is no need for quenching after nitriding, simplifying the process.
• Disadvantages: The nitrided layer is thin, with a relatively low load-bearing capacity. The nitriding time is long and the cost is high.