NITRIDING

Brett Iseneker

History of nitriding

Dr. Adolph Fry in the 1900sFigured out that iron and nitrogen had an attraction to each other1906 he developed the iron-nitrogen equilibrium diagramThe process was discovered around the same time in the United States and Germany but wasn’t used much until after world war 2

• Heat is applied to both iron and a nitrogen gas• The nitrogen will

diffuse into the surface of the steel and create a change in the surface of the

steel• This gas nitriding

process will harden the steel

What metals is nitriding used on?

• Aluminum• Steel• Titanium• Molybdenum

BENEFITS OF NITRIDING

• Higher surface hardness• Increase wear resistance• Improve fatigue life• Improve corrosion

resistance (except for stainless steels)

• Stop metals from softening when being heated

Benefits

• Reduced cylinder wall wear - the harder a surface the more difficult to wear down

• Improved piston ring life from a straight cylinder wall when engine is hot, and a better job of sealing

• Nitriding allows use of chrome plated piston rings, which are more wear resistant and will work with hardened steel

• Increase tensile strength

Gas Nitriding process

• Nitrogen into the surface layers of alloy steel of almost finished parts to an atmosphere of ammonia gas

• Requires special heat treating furnaces which are air tight and can hold the parts at a high temp

• At 975 degrees, the ammonia gas flowing into the furnace is broken down into elements of hydrogen and nitrogen

• Nitrogen will enter the surfaces of the steel. The process takes 25-80 hours

Different types of nitridingGas Nitriding ( explained above)

Salt Bath Nitriding- uses nitrogen that has cyanide salt, the salts give carbon to the part being nitrided and gives it a nitrocarburizing process. Temperatures are around 1022–1094 degrees F. This can be done in 4 hours so it is much quicker than gas nitridingPlasma Nitriding-Doesn’t react because of heat but because of the gas in ionized state. electric fields are used to make ionized molecules of the gas around the part or surface to be nitrided. Highly active gas with ionized molecules is called plasma. The gas used for plasma nitriding is usually pure nitrogen

Disadvantages of each process

• Gas nitriding -Any dirt or oil on the surface of the metal being treated will not come out right. Has to be prepped carefully. Ammonia as a nitriding is toxic if inhaled

• Plasma nitriding- more costly than other ones• Salt bath nitriding- salts used are highly toxic

Nitriding Problems

Commonly nitrided parts

Gears• Crankshafts

• Camshafts Valves

• Cylinders

• Tooling• Landing gear parts• Shafts that are exposed to weather• Stainless Steel shafts• Piston rings• Springs• Fuel injectors

• Gas Nitriding furnace