MOLTEN SALT (NT-1) BATH NITROCARBURIZING
Salt bath nitrocarburizing is used for decades in a wide range of industries. It is used to improve wear resistance and fatique strength of cast iron, sintered iron and steel. In combination with oxidation bath it improves corrosion resistance and reduces surface roughness.
Nitrocarburizing is an alternative to case hardening, chrome plating and many other coating processes. It is also an alternative to plasma or gas nitrocarburizing with equally good or improved quality and a better economy.
Because of low processing temperature (just below 600oC ) it has the advantage of inducing little shape distortion during the hardening process.
Molten Salt Bath Process Using NT-1 Salt:
Our company’s production NT-1 is the base salt for the nitrocarburizing molten salt baths. NT-1 is in molten state at operating temperature of 580oC . It is generally melted in titanium or some other special pots.
The reactive components in NT-1 are alkali cyanates and during nitrocarburizing operation they are converted to carbonates with little changes in the overall composition of the bath. The amount of cyanates is kept stable in certain limits by a polymer regenerator; NT-Reg. Usage of NT-Reg converts the carbonates to cyanates without any volume change in the pot.
NT-1 and NT-Reg are sold in powder form in 25 Kg polyethylene bags and in tablet form in 25 Kg polyethylene bags, respectively. Both of them are classified neither as toxic nor harmful.
Molten salt bath nitrocarburizing can be used together with an oxidizing bath as a quenching medium. Our company’s production NT-Oksi works between 370-420oC and oxidizes the surface to black iron oxide (magnetite). It is sold in 25 Kg polyethylene bags.
Oxidized and polished material can be oxidized a second time in order to further increase the corrosion resistance and decrease the surface roughness.
Overall heat treatment can be illustrated as in the graph below.