What Is Cyaniding?

Are you curious to know what is cyaniding? You have come to the right place as I am going to tell you everything about cyaniding in a very simple explanation. Without further discussion let’s begin to know what is cyaniding?

In the world of metallurgy and materials engineering, the quest for enhancing the properties of metals has led to the development of various surface hardening techniques. One such method that has stood the test of time is “cyaniding.” This age-old process, dating back to the 19th century, involves the diffusion of carbon and nitrogen into the surface of a metal to create a hardened outer layer. Through cyaniding, engineers can significantly improve the wear resistance and strength of metals, making them ideal for applications in machinery, tools, and other industrial components. In this blog, we will explore the cyaniding process, its mechanism, and its applications, as well as the key factors that make this surface hardening technique so valuable in the world of metallurgy.

What Is Cyaniding?

Cyaniding is a surface hardening process that involves the introduction of carbon and nitrogen into the surface layer of a metal. It is primarily used for low-carbon and low-alloy steels, as well as some cast irons. The process creates a thin, hardened layer on the surface of the metal, known as a “case,” while the core remains relatively soft and tough.

The Cyaniding Process:

The cyaniding process is carried out in a cyanide salt bath, typically containing sodium cyanide. The metal component to be treated is heated to a specific temperature (usually between 850°C to 950°C) and then immersed in the cyanide bath. At this elevated temperature, carbon and nitrogen atoms diffuse into the metal’s surface, forming metal carbides and nitrides, which are harder than the base metal. The depth of the hardened layer can be controlled by adjusting the temperature and the duration of the treatment.

Mechanism And Advantages:

The cyaniding process works on the principle of diffusion. The carbon and nitrogen atoms from the cyanide bath diffuse into the lattice structure of the metal, occupying the interstitial spaces between the metal atoms. This creates a hardened surface layer with enhanced wear resistance and improved hardness, while the core remains relatively unaffected.

The Advantages Of Cyaniding Include:

  1. Increased Surface Hardness: Cyaniding significantly increases the surface hardness of the metal, making it more resistant to wear and abrasion.
  2. Improved Fatigue Strength: The hardened layer created by cyaniding enhances the fatigue strength of the metal, making it less prone to failure under repeated stress.
  3. Cost-Effectiveness: Cyaniding is a relatively cost-effective surface hardening process compared to some other techniques like carburizing or nitriding.


Cyaniding finds extensive applications in various industries, including:

  1. Machinery and Tooling: Cyanided components are widely used in machinery and tools, such as gears, cams, shafts, and cutting tools, where wear resistance and hardness are essential.
  2. Automotive: Some automotive components, such as crankshafts and gears, are cyanided to improve their surface properties.
  3. Aerospace: Certain aerospace components benefit from the improved wear resistance and strength provided by cyaniding.


Cyaniding is a time-tested and effective surface hardening process that has played a significant role in enhancing the properties of metals for over a century. By creating a hardened outer layer with improved wear resistance and strength, cyaniding has found applications in diverse industries, from machinery and tools to automotive and aerospace. As materials engineering continues to evolve, cyaniding remains a valuable tool in the arsenal of surface hardening techniques, contributing to the creation of durable and reliable components that power our modern industrial world.

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What Is Cyaniding Used For?

Cyaniding or pack cyanide carburizing is used to case harden steel. It generates a very thin but hard outer case. Cyaniding is a case-hardening process in which both carbon and nitrogen in form of cyaniding salt are added to the surface of parts machined from low- to medium-carbon steels.

What Is Cyaniding In Heat Treatment Process?

Cyaniding, or salt bath carbonitriding, is a heat treating process that produces a file-hard, wear-resistant surface on ferrous parts. When steel is heated above Ac1 in a suitable bath containing alkali cyanides and cyanates, the surface of the steel absorbs both carbon and nitrogen from the molten bath.

What Is The Difference Between Nitriding And Cyaniding?

It is one of the most widely used surface hardening processes. The process involves diffusing carbon into low-carbon steel to form a high-carbon steel surface. Cyaniding: In this process of surface hardening, both carbon and nitrogen are added to the surface layer of steel (ferrous material, usually low carbon grade).

What Is Metal Cyaniding?

Cyaniding is a fast and efficient case-hardening process that’s typically used on low-carbon steels. It introducing carbon and nitrogen into a solid ferrous alloy by holding above Ac1 in contact with molten cyanide or suitable composition.

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