Nitriding steel grades:

 

Grades
41CrAlMo7-10 - 1.8509 - 34CrAlMo5-10 - 1.8507 - Chrome-molybdenum-aluminum nitriding steel
34CrAlNi7-10 - 1.8550 - 34CrAlNi7 - 1.2891 - chromium-nickel steel for nitriding with aluminum additive
31CrMo12 - 1.8515 - Chromium-molybdenum nitriding steel
31CrMoV9 - 1.8519 - Chrome-molybdenum-vanadium nitriding steel
32CDV13 - 33CrMoV12-9 - 1.8522 - 32CrMoV12-9 - Chrome-molybdenum-vanadium steel for nitriding
40CDV12 - 40CrMoV13-9 - 1.8523 - 39CrMoV13 - Chrome-molybdenum-vanadium steel for nitriding

 

Nitriding as heat-chemical treatment

Nitriding is the process of saturating the top layer of a product by penetrating the nitrogen atoms most often in a dissociation stream of ammonia. Saturation is carried out at elevated temperatures over a longer period of time, as applicable for each grade of steel and article.

During the whole process, the steel acts as a catalyst for ammonia decomposition, and before the nitrogen molecules are joined, the atoms are absorbed into the surface of the product in the interstitial spaces of the spatial net creating dispersion and hard nitrides. In this way, the product achieves a much higher hardness of the top layer compared to carbon steels or steel for thermal improvement.

Steels for nitriding - characteristics and specifications

Other advantages of nitriding steel are increased abrasion resistance, higher sliding properties of the hardened surface and increased fatigue resistance.

Steels for nitriding in relation to carbon steels have 2 to 4 times higher hardness and abrasion resistance after imparting properties, and consequently, increased susceptibility to brittleness. The internal structure of the products is exposed to the frequent occurrence of cracks when used inappropriately.

Nitriding steels have also been reported to have increased corrosion resistance in environments where iron chloride, seawater, liquid oils, superheated steam, air vapor, and alkaline solutions are present.

The nitriding steel typically in the softened state is first subjected to a thermal improvement process after pre-machining and cutting of long products into shorter components. Prior to nitriding, the product should be carefully cleaned of rust, grease and oil, sharp edges causing material fragility, decarbonized surface should be cleaned leaving the finished product practically ready.

Other unevenness must be leveled with chip or grinding and stressed by tempering at a temperature above the nitriding temperature. Also note that nitriding components after the process can slightly increase their volume – approx. + 0.02% for the diameter of surface.

Application and heat treatment

The nitriding process is usually carried out at temperatures of 480-570 ℃. The higher the process temperature, the faster the nitrogen atoms enter the steel surface. If the nitriding temperature is too high, there is a risk of inversely proportional decrease in product hardness. Nitriding steels usually contain aluminum – Al, Chrome – Cr, Molybdenum – Mo. There are also steel with the addition of Vanadium and Titanium. Apart from the basic grades - 38HJ, 38HMJ, 33H3MF, materials such as 40H2MF or 35HM are also nitrided.

Nitriding steels are used for components and subassemblies of motors, machines, vehicles such as camshafts, cogwheels, piston pins, crankshafts, engine cylinders, piston rods, nitriding rods and tubes, grinding spindles and milling machines, valve plates, superheated steam valves, crankshafts, diesel fuel pump components, bushings and cylinders in pneumatic machines or push rods.

Bars and forgings of steel for nitriding

Nitriding steel described above is defined by PN-72/H-84034, PN-89/H-84030.03 standards and EN-EN 10085 European Norms; we supply:


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