- What is Titanium Nitriding?
- What does the actual nitriding process do at a molecular level?
- How does liquid nitriding change the materials properties?
- What are the benefits of the nitride process in material performance?
- What is the actual process when carrying out liquid nitriding?
- Why have an optional mechanical finishing and polishing process?
- What are the alternative nitriding processes to liquid nitriding?
- What are the alternative finishes to nitriding?
Diamond Like carbon (DLC)
- What is Diamond Like carbon (DLC)?
- What is the limitation of the Diamond Like Carbon (DLC) process?
- What is Physical Vapor Deposition (PVD)?
- What are the attributes of PVD / DLC coatings?
Military weapon applications
Sectors and applications
Titanium Nitride Technology
What is Titanium Nitriding?
Titanium nitriding modifies the surface metallurgy properties of Ferrous materials by dramatically hardening the surface that improves performance as well as extending product life.
The process is a thermo-chemical diffusion treatment that enriches the surface of ferrous materials with nitrogen and a small amount of carbon. Thermochemical treatment employs thermal diffusion to incorporate non-metal or metal atoms into a material’s surface to modify its chemistry and microstructure.
What does the actual nitriding process do at a molecular level?
There are three molecular layers created with nitriding. These are as follows in order from the surface:
- Oxide layer
- Compound Layer
- Diffusion layer
The three layers form an effective protective barrier offering different properties:
Top Oxide Layer
- Corrosion resistance
- Impregnate micro-porosity. Low-friction, running-in Layer
- Black finish
Middle Compound Layer
The Compound Layer (CL) is essentially iron nitrides and special nitrides (in case of alloyed steels) plus some iron oxides. This provides the following benefits:
- Very high hardness. Abrasion wear resistance.
- Adhesive wear / Scuffing resistance
- Low Friction
Final Diffusion Layer
The area below the compound layer where Nitrogen diffuses into the iron lattice forms a solid solution. This provides the following benefits:
How does liquid nitriding change the materials properties?
The nitriding process increases the hardness of the outer surface. Values of hardness after nitriding are typically 600 to 1200 HV (dependent on the grade of steel, alloying elements & carbon content). This is compared to the original surface of approximately 100-250 HV and represents an increase in hardness of 3-6 times.
It also changes the surface energy properties of the surface. It reduces friction, making the surface more lubricious.
What are the benefits of the nitride process in material performance?
The benefits include:
- Very good wear resistance
- Excellent corrosion protection
- Good surface fatigue resistance
- Decorative black surface
- Good frictional properties
- Excellent scuffing / seizure protection (adhesive wear) thanks to ceramic characteristics of the surface
- No distortion. Hence treatment can be done on finished parts
- Environmentally sound; “zero waste” concept
- Uniform compound layer thickness (typical ~ 10 microns or 0.0005”) on complex part geometries.
- Ability to treat small cavities and through holes – e.g., barrels.
- Consistent & durable black finish – matte or satin.
What is the actual process when carrying out liquid nitriding?
There are several stages in the liquid nitriding process.
These are as follows:
- Degrease & rinse. An alkaline aqueous wash process at 160F
- Drying. Carried out at 150F
- Pre-heat: 725F to 775F
- Nitride: 30-120 min. 950F to 1100F
- Oxidise: 10-20 min. 750F-850F
- Cascade rinse: Wash parts to remove residue.
- Mechanical finishing / Polishing (optional)
- Impregnation: Improve corrosion resistance
Why have an optional mechanical finishing and polishing process?
What are the alternative nitriding processes to liquid nitriding?
Ion-plasma nitriding. It is a plasma supported thermochemical hardening process used to increase wear resistance, surface hardness and fatigue by generation of a hard layer including compressive stresses.
What are the alternative finishes to nitriding?
Diamond Like Carbon (DLC) is an excellent alternative to nitriding where a higher hardness and even lower friction is required compared to the nitride process. Also, it is a low temperature process (< 400°F) so there is no distortion of parts during coating. Finally, there is a very high adhesion level of the coating to the surface.
Diamond Like Carbon technology
What is Diamond Like carbon (DLC)?
Diamond Like Carbon is a process where the carbon atoms are rearranged in a special crystal array (sp3-lattice). The finished DLC surface has the combined properties of diamond that is a very hard compound and graphite that is very low friction.
This means the DLC coating provides the following benefits:
- Ultra-low friction between sliding components. This prevents jamming of moving / sliding parts and ensures more reliable operation.
- Reduces the need for frequent lubrication. Low or no-lubrication conditions minimize dirt and dust accumulation. This reduces servicing requirements.
- Reduced carbon fouling due to the ‘non-sticking’ nature of the DLC coating.
- A very high hardness surface layer that significantly improves scuffing and overall wear-resistance.
- Appealing cosmetic finish.
What is the limitation of the Diamond Like Carbon (DLC) process?
The DLC process is limited in that through-holes and small cavities cannot be coated uniformly. However, the coating thickness is typically in the range of 2 to 4 microns (0.0001” – 0.0002”) so there is minimal change in dimensions of uncoated parts.
Physical vapor deposition (PVD) is a thin-film coating process which produces coatings of pure metals, metallic alloys and ceramics with a thickness usually in the range 1 to 10µm. Physical vapor deposition, as its name implies, involves physically depositing atoms, ions or molecules of a coating species on to a substrate. There are 3 types or processes of PVD:
There are advantages and disadvantages to each and we are happy to discuss these with you.
What are the attributes of PVD / DLC coatings?
There are many attributes to consider with PVD/ DLC coatings. They include:
- They are the hardest known synthetic materials (1500 – 4500 HV). Therefore, they have a high resistance to wear, abrasion and erosion.
- They are thin coatings (2 to 5 microns). So, they have minimal impact on size tolerance of the coated component.
- It is a low coating temperature process (150 – 250C). Therefore, there is no distortion of coated component or loss of core hardness.
- The process provides low friction coefficients of the surface (0.1 – 0.5). This minimizes friction losses and power.
- The process can be used to deposit onto alloyed and multi-layered coatings.
- They are high adhesion coatings for a wide range of substrates. This includes all steels including sintered, copper-alloys, titanium- alloys, tungsten-carbide, plastics and glass.
- It is possible to mask regions on the component where no coating is desired.
- The process has zero environmental impact. There are no effluents or discharges and there are no toxic chemicals.
- It is a line of sight process so it can be difficult to coat cavities or IDs.
Military weapon applications
Why nitride gun components like barrels and slides?
Nitriding provide firearms with the four primary characteristics they require:
- Improved wear, erosion and scuffing resistance: A treated firearm will fire 15,000+ rounds with no adverse effects on the bore due to erosion and small internal components benefit from increased wear resistance.
- Reduced friction at the surface. Benefits include increased muzzle velocity that leads to a flatter long distance trajectory and better accuracy.
- Corrosion protection: A firearm has much higher resistance to environmental corrosion. The process also provides superior protection when corrosive ammunition is used.
- Uniform durable black finish: Nitriding provides a more durable uniform consistent finish on firearms which can be expanded to other parts including sights, magazines etc.
What parts of guns benefit from nitriding?
Many parts of a firearm can be protected. This includes gun slides, barrels, frames, magazines and many of the small parts such as safeties, slide release, mag catch and picatinny rails. They are treated to improve corrosion and wear.
Sectors and applications for Nitriding and Diamond Like Carbon
What sectors are nitriding and diamond like carbon used in?
- Agricultural Machinery
- Drilling Equipment
- Industrial Blades
- Manufacturing Equipment, Tools
Find out more about Kronos Protection
To find out more contact us now on +1 208 333 9496 or use our contact us page. Or click Kronos Protection application technologies to find out more about our advanced, state of the art, coating surface treatments.