WFM GROUP IS A MANUFACTURER OF COATING MATERIALS TO PROTECT PARTS FROM WEAR

Surface hardness .

Hardness is important from an engineering point of view because resistance to wear by friction or erosion by steam, oil, and water usually increases with hardness. 

Hardening or surface hardening is a process in which the hardness of the surface (body) of an object increases, while the interior of the object remains elastic and strong. After this process, surface hardness, wear resistance and durability increase. This is achieved by several processes, such as carburizing or nitriding, by which the component is exposed to a carbon or nitrogenous atmosphere at high temperature. As it was written, two main characteristics of the material affect:

• Hardness and wear resistance are significantly increased . In materials science,  hardness  is the ability to withstand  surface indentation ( localized plastic deformation ) and  scratches . Hardness is perhaps the most ill-defined property of a material because it can indicate scratch resistance, abrasion resistance, indentation resistance, or even resistance to forming or local plastic deformation. Hardness is important from an engineering point of view because resistance to wear by friction or erosion by steam, oil, and water usually increases with hardness.
• Does not have a negative impact on strength . Viscosity  is the ability of a material to absorb energy and plastically deform without breaking. One definition of viscosity (for high strain rate,  fracture toughness ) is that it is a property that indicates a material’s resistance to fracture in the presence of a crack (or other stress concentration defect).

The hardness of the material correlates with its wear resistance. If the hardness of the material itself is less than the hardness of the abrasive substance, then the rate of wear is high. The hardness of the material plays a major role in wear resistance. Some materials exhibit special wear characteristics.

Wear resistance of the material.

Abrasion of a material is the mechanically induced damage to a surface that results in the gradual removal of material due to relative motion between that surface and the substance or substances in contact. The contacting substance may consist of another surface, a liquid, or solid abrasive particles contained in some form of liquid or suspension, such as a lubricant. As with friction, the presence of wear can be both positive and negative. 

Productive, controlled wear can be found in processes such as machining, cutting, grinding, and polishing. However, in most technological applications, the appearance of wear is highly undesirable and an extremely expensive problem as it leads to component degradation or even failure. From a safety perspective, this is often not as serious (or as sudden) as a fracture. This is because wear and tear is usually expected.

Certain characteristics such as hardness, density and density can have a decisive effect on the wear resistance of a material. Wear and tear has several types and is somewhat unpredictable. It is rather difficult to test and evaluate in the laboratory or during operation.

Загалом знос — це механічно спричинене пошкодження поверхні, яке призводить до поступового видалення матеріалу через відносний рух між цією поверхнею та речовиною або речовинами, що контактують. Тому існує ідеальний зносостійкий матеріал, і в кожному випадку він сильно залежить від багатьох змінних (наприклад, комбінації матеріалів, контактного тиску, середовища, температури). 

• In general, wear is mechanically induced damage to a surface that results in the gradual removal of material due to relative motion between that surface and the substance or substances in contact. Therefore, there is an ideal wear-resistant material, and in each case it is highly dependent on many variables (eg material combination, contact pressure, environment, temperature). 

  Some materials exhibit special wear characteristics. The most typical wear-resistant materials:

  • Ni  ₃ Al is an alloy . 

  Nickel aluminide is an intermetallic alloy of nickel and aluminum with properties similar to both ceramics and metals. Nickel aluminide is unique in that it has very high thermal conductivity combined with high strength at high temperature. These properties, combined with its high strength and low density, make it ideal for special applications such as blade coatings in gas turbines and jet engines. Composite materials with alloys based on Ni  ₃  Al as a matrix reinforced with, for example, TiC, ZrO2, WC, SiC and graphene are advanced materials. In 2005, the most wear-resistant material was reportedly created by embedding diamonds in a matrix of nickel aluminide.

  • Tungsten carbide . 

  In mining and beneficiation, impact wear has the greatest impact. Extraction and processing of minerals require wear-resistant machines and assemblies, since the energies and masses of the interacting bodies are significant. For this, it is necessary to use materials with maximum wear resistance. For example, tungsten carbide is widely used in mining in top hammer drill bits, downhole hammers, roller cutters, long wall bits, long wall shears, borehole reamers and tunnel boring machines.

  • Silicon carbide . 

  Silicon carbide is an extremely hard, synthetically produced crystalline compound of silicon and carbon. Its chemical formula is SiC. The Mohs hardness of silicon carbide is 9, which is close to the hardness of diamond. In addition to their hardness, silicon carbide crystals have fracture characteristics that make them extremely useful for grinding wheels. Its high thermal conductivity, together with high-temperature strength, low thermal expansion, and resistance to chemical reactions, make silicon carbide valuable in the production of high-temperature applications and other refractories.

  • Malleable cast iron.

   very similar in composition to gray cast iron, but during solidification, graphite forms nuclei in the form of spherical particles (nodules) in ductile cast iron, and not in the form of flakes. Typical applications for this material include valves, pump housings, crankshafts, gears and other automotive and machine components due to its good machinability, fatigue strength and higher modulus of elasticity (compared to gray cast iron), and in heavy duty gears due to its high yield strength and wear resistance .

  • Aluminum bronze . 

  Aluminum bronzes are a family of copper-based alloys that offer a combination of mechanical and chemical properties unmatched by other alloy series. They contain from 5 to 12% aluminum. Aluminum bronze is finding increasing acceptance for a wide range of applications that require resistance to mechanical wear. Its wear resistance is based on the transition from a softer metal (aluminum bronze) to a harder metal (steel) and the formation of a thin layer of a softer metal on a harder metal.

The most common modern methods of increasing wear resistance:

• Alloys with coating . 

Hardening by surface treatment can be further classified as diffusion treatment or localized heat treatment. Diffusion methods introduce alloying elements that reach the surface by diffusion, either as solid solution agents or as hardening agents that promote martensite formation during subsequent quenching. In this process, the concentration of the alloying element on the surface of the steel component increases. Diffusion methods include:

• Carbonation.

It is a carburizing process in which the concentration of carbon on the surface of a ferrous metal alloy (usually low carbon steel) is increased by diffusion from the environment. Carburizing produces a hard, highly wear-resistant surface (medium body depth) of a product with excellent contact load capacity, good flexural fatigue strength, and good burr resistance.

• Nitriding.

It is a carburizing process in which the concentration of nitrogen on the surface of the iron is increased by diffusion from the environment to create a carburized surface. Nitriding gives a hard, highly wear-resistant surface (shallow body depth) to the product with sufficient ability to withstand contact loads, good bending fatigue strength and excellent burr resistance.

• Drilling

It is a thermochemical diffusion process, similar to nitrocarburizing, in which boron atoms diffuse into the substrate to create hard and wear-resistant surface layers. The process requires a high processing temperature (1073-1323 K) and a long duration (1-12 hours) and can be applied to a wide range of materials such as steels, cast iron, cermets and non-ferrous alloys.

• Titanium nitride strengthening .

Titanium nitride (an extremely hard ceramic material) or titanium carbide coatings can be applied to tools made from this type of steel using a physical vapor deposition process to improve performance and tool life. TiN has a Vickers hardness of 1800–2100 and a metallic gold color.

• Hardened steels . 

To increase the wear resistance of steels, cementation is usually carried out on the basis of martensitic transformation. Martensitic hardening is one of the most common hardening methods, mainly used for steels (i.e. carbon steels as well as stainless steels).

• Flame hardening .

Flame quenching is a surface hardening technique that uses a single torch with a specially designed head to provide very rapid heating of the metal, which is then rapidly cooled, usually with water. This creates a “case” of martensite on the surface, while the interior of the object remains ductile and strong. This is a similar technique to induction hardening. This type of strengthening requires a carbon content of 0.3–0.6 wt.% C.

• Induction hardening. 

Induction hardening is a surface hardening technique that uses induction coils to heat the metal very rapidly, which is then rapidly cooled, usually with water. This creates a “case” of martensite on the surface. This type of strengthening requires a carbon content of 0.3–0.6 wt.% C.

• Laser hardening . 

Laser hardening is a surface hardening technique that uses a laser beam to heat the metal very rapidly, which is then rapidly cooled (usually by self-quenching). This creates a “case” of martensite on the surface, while the interior of the object remains ductile and strong.

The importance of durability.

If a part is subject to wear and tear, it can become ineffective, inefficient, or even dangerous over time. Parts printed with wear-resistant material are more durable, so they can be used longer without replacement. 

In addition to wear resistance, it is important to consider the coefficient of friction of the material. It refers to the amount of resistance that a substance exerts on the material moving over it. Plastics typically have a low coefficient of friction, making plastic materials prime candidates for wear-resistant parts, such as for 3D printing.

Wear-resistant materials are often used in mechanical engineering, as well as in the automotive and electronics industries – or in any environment where component parts have  moving parts – such as gears, bushings or bearings – that are prone to damage from wear. Thus, wear-resistant materials are key.

Advantages of wear-resistant materials:

• Parts used during assembly or production will require less maintenance and less frequent replacement. This ensures that workflows remain fast and costs are kept to a minimum.
• When manufactured from wear-resistant materials, the parts will last longer and will be more durable, which will lead to lower costs.