This type of wear can be classified as follows:
Low-Stress Abrasion: Wear resulting from contact between the abrasive and the base material without any impact or compressive force.
Medium-Stress Abrasion: This is wear caused by the abrasive material coming into contact with two base materials without impact or compressive force. Since there is no impact effect in this type of wear, the ductility of the base material is not a significant factor. As long as the base material’s hardness is higher than that of the external element (abrasive), the wear rate remains quite low. Hardened parts, heat-treated steel plates, and ceramic components are used to resist this type of wear (for example, those with a hardness value of 400 HB).
High-Stress Abrasion / Under Compressive Force: Abrasion under high compressive force occurs in equipment where the abrasive is compressed between two surfaces and subsequently breaks into many fragments. Under the influence of high compressive force, surface wear, chipping, pitting, fracture of hard phases (carbides, borides, etc.), or plastic deformation of the matrix may occur. Therefore, in surface coating applications, attention must be paid to optimizing yield strength, ductility, and hardness.
For example, coal crushers are types of equipment exposed to these types of wear effects.
Severe Abrasion (Pitting Abrasion) / High Impact: This term refers to a combination of low, medium, and high levels of wear accompanied by impact. This type of wear results in the detachment of large pieces from the base material and the formation of scratches. Additionally, situations accompanied by plastic deformation may occur.
Another solution for pitting abrasion is the use of ductile materials capable of withstanding shocks (force applied to a single contact point) and impacts (force applied to multiple contact points). In applications involving repeated shocks and impacts, manganese steels are often preferred, while titanium carbide alloys also demonstrate resistance to impacts.
For example, crusher hammers are equipment exposed to this type of wear.
Adhesion/Friction: The process in which two metal bodies rub against each other, causing material to transfer from one surface to another, is referred to as “Adhesion/Friction Wear.” This type of wear occurs under conditions of high temperature, high pressure, and friction.
Since it occurs at the microscopic level, this type of wear is generally invisible to the naked eye. The rate of friction wear depends on several factors, such as the moving force between the two surfaces, speed, the temperature of the operating environment, surface condition, and surface friction coefficients.
Additionally, the type of base material in the operating environment also has a significant effect. The use of materials with identical crystallographic structures increases the risk of frictional wear.
For example, continuous casting rollers, cutters, and bearing housings are among the equipment exposed to this type of wear.
Erosion: Erosion shares similarities with abrasion. This type of wear occurs when solid particles or liquid droplets strike a surface at high speeds. The wear rate varies depending on the angle of attack and the speed of the external elements. The physical properties of the base material also determine the wear rate caused by erosion.
At low attack angles (less than 30°), the amount of wear may be comparable to that caused by low- or medium-stress abrasion. The wear rate is directly related to the hardness of the base material. At higher angles of attack (30 to 90°), abrasive particles can deform the base material and cause parts to break off. In such cases, impact-resistant materials capable of absorbing the energy generated by the impact must be used to prevent impact-induced deformation or cracking.
For example, equipment operating in environments where sludge and sediment accumulate is exposed to this type of wear.
Cavitation: Cavitation occurs in highly turbulent fluids in contact with a solid surface. The fluid and bubbles strike the material surface at high speeds, creating small voids, and wear occurs during this process. This phenomenon is also known as “cavitation erosion.”
Repeated cavitation leads to wear and fatigue of the base metal. This fatigue can cause cracks to form and, consequently, component failures. Materials with high toughness values demonstrate greater resistance to this type of erosion by absorbing the energy released when the voids implode.
For example, hydroelectric turbine blades are among the components exposed to cavitation.
Thermal Fatigue: This type of fatigue refers to wear caused by thermal cycling loads on the base material. When a part is repeatedly heated and cooled, expansion and contraction occur. These processes lead to surface cracks known as “thermal fatigue cracks.”
For example, forging tools and hot rolling rolls are components subject to this type of fatigue.
Vibrational Wear: While the types of wear mentioned earlier result in continuous material loss, “vibrational wear” occurs when repetitive rolling or sliding motion takes place between two components. Under these conditions, sudden material loss in the form of pitting or gouging is observed. Parts that roll or slide under high pressure are subjected to heavy mechanical loads. This situation can lead to the formation and propagation of cracks under load, resulting in flaking or gouging effects.
Examples include gear teeth, rails, rollers, and rolling mills.
Corrosion: Corrosion is a broad and complex form of wear. Coating solutions are frequently used to prevent this type of wear. Austenitic stainless steels (300 series) and nickel-based alloys are particularly used.
In the qualification tests for these coatings, no crack formation is expected, especially in 180° bend tests. In terms of hardfacing applications, corrosion generally does not pose a significant problem.
Examples include paper spiral carriers with hardfacing containing tungsten carbide in a nickel matrix and continuous casting rollers coated with martensitic stainless steel.
Combined Abrasion: In some applications, components may be exposed to more than one type of stress and wear simultaneously. Multiple abrasion results from a combination of different types of wear. Corrosion and/or high temperatures, when combined with other types of wear, can create conditions known as secondary factors.
