Liquid Nitriding is a surface treatment process that produces a black in color finish that is very hard and corrosion resistant. It combines a high surface hardness with increased corrosion resistance. The process begins with the cleaning and super-polishing of the material to a surface roughness of 6 to 10 Ra. The steel bars or components are then fixed vertically, and submerged into an electrically controlled liquid tank.
Salt Bath Nitriding Steps - ARCOR Process
Smooth component surface to requirements, improve friction properties
2.DEGREASING / RINSING
Remove all oils and other particulates from the components surface
Maintain a stable temperature in the process
Surface structure conversion
The nitride layer is oxidized to increase corrosion resistance producing the black finish
Remove salt from the component surface, wipe clean with oiled rag
This process; through thermochemistry nitrocarburizes the steel at temperatures within the range of 930 to 1150 degrees Farenheit in a specially formulated Nitrogen-bearing salt bath. The Nitrogen diffuses into, and chemically combines with the nitride forming elements in the metal. The steel's surface is thus converted to iron nitride to a typical depth of up to .001", based on product requirements. This surface is very uniform, increasing the surface hardness above 55 Rc. Beneath the iron nitride layer is a nitrogen-enriched, hardened diffusion zone. The diffusion zone functions as a lightly hardened case with a hardness ranging from around 55 Rc just below the iron nitride layer to approximately 40 Rc at a depth of approximately.010". Results vary depending on the base material being used as there are many types of metal that can be nitrocarburized. Oxidizing is employed to produce the black, corrosion resistant surface film.
Nitrided hydraulic cylinder rods offer the following benefits over conventional hard chrome:
Surface hardness above 55Rc
Surface finish 16 Ra or better
0.001" thickness per side (0.0254mm)
Improved corrosion resistance
Salt spray tested (ASTM B117) to 100 hours min. with zero corrosion
Improved wear & dent resistance
Improved oil retention (longer seal life)
No surface pitting, flaking or micro-cracking
Environmentally friendly process compared to chrome plating
Once the cylinder shaft or rod is assembled into a cylinder and put into service the hydraulic fluid on the surface provides additional corrosion resistance which is normally sufficient to protect the shaft during its entire life. However, there are occasions when the shaft is not being worked and when the surface is exposed to a corrosive environment. For example, brand new equipment may be stored outside for a considerable period of time at a manufacturer's plant, or an equipment dealer may hold inventory before it is sold. In these instances it is best to provide some additional corrosion protection. An inexpensive application of a rust preventative mixture can be applied to prevent corrosion and thereby preserve the quality of the nitride and the life of the cylinder.
Nitriding produces a surface finish that is very hard, corrosion resistant, environmentally friendly & cost effective alternative that offers excellent performance when compared to hard chrome plating.