WEAR-RESISTANT CAST IRON  

WEAR-RESISTANT CAST IRON is a special alloy cast iron with high hardness and excellent anti-friction properties, widely used for the manufacture of mechanical parts such as machine tool guides, mill rolls, ball mill lining plates and other engineering components. The basis of the production process is the regulation of the chemical composition, control of the cooling rate and special heat treatment regimes to obtain the required microstructure. Below is a systematic description of the manufacture of wear-resistant cast irons.

Depending on the operating conditions, wear-resistant cast irons are divided into two main categories, each of which has its own production priorities:

Anti-friction cast irons (working under lubrication conditions)

Scope of application: machine guides, piston rings, cylinder liners, etc.

Manufacturing principle: a relatively soft base is required to retain the lubricant, while simultaneously containing hard phases to absorb friction. Typically, pearlitic gray cast iron or high phosphorus cast iron is used as a base.

Key technological operations: increasing the phosphorus content (0.4%–0.6%) to form a high-hardness phosphide eutectic, as well as alloying with chromium, molybdenum, copper and other elements to strengthen the base, increase strength and resistance to seizing.

Wear-resistant cast irons (working under conditions of dry friction or abrasive wear)

Scope of application: lining plates of ball mills, plowshares, rolling rolls, crusher hammers, etc.

Manufacturing principle: high and uniform hardness throughout the entire volume is required; wear resistance is provided mainly by carbides in white cast iron.

Key technological operations: Based on white cast iron with the addition of alloying elements (chromium, molybdenum, nickel, vanadium), alloyed white cast iron is obtained, or a “bleaching” process is used to obtain a surface layer of white cast iron while retaining gray cast iron in the core.

CHEMICAL COMPOSITION CONTROL

The ratio of alloying elements is a determining factor in the properties of wear-resistant cast iron:

Carbon (C) and silicon (Si): carbon is the basis for the formation of carbides, increases wear resistance, but reduces viscosity; silicon promotes graphitization. Wear-resistant cast irons typically use low-carbon and low-silicon compositions to promote the formation of a bleached structure.

Chromium (Cr): one of the most important alloying elements. Chromium forms highly hard carbides of the (Cr,Fe)₇C₃ type, significantly increasing wear resistance and hardenability. In high-chromium cast irons, the chromium content can reach 26%–32%.

Molybdenum (Mo), Nickel (Ni), Copper (Cu): These elements are used primarily to increase the hardenability of the base, promoting the formation of a martensitic or bainite structure, which improves toughness while maintaining hardness.

Manganese (Mn): stabilizes austenite; in medium-manganese high-strength cast irons, its content is increased (5%–9.5%), which contributes to the formation of the structure of martensite and retained austenite.

Impurity control: Sulfur (S) and phosphorus (P) contents must be strictly controlled (typically ≤ 0.1%) to prevent hot cracking and reduce toughness.