Lerman, P. and de Almeida, R., "Heavy Duty Valves with Enhanced Performance through Nitriding Treatment," SAE Technical Paper 2015-36-0240, 2015, doi:10.4271/2015-36-0240.
Nitriding is a well-known treatment in many engine components. In valves, it is very common on light vehicle applications. For heavy duty platforms, its use has been restricted due to considerations on temperature and structural resistance. However, it is known to be a very interesting concept regarding tribology, especially wear resistance, with a suitable compromise on cost. Due to the continuous increase of engine loads to attend different emission legislations, wear resistance became a key issue for valves.MAHLE developed a nitriding treatment to be applied on Heavy Duty valves presenting superior wear resistance and suitable structural performance. Deep product validation is presented through rig and engine tests.Not less important is the introduction of gas nitriding as an environmentally friendly process in replacement of the traditional and almost unique technique to proper nitride valve alloys, salt bath nitriding. Gas nitriding will assure the same valve performance with the advantage of employing a lower nitriding temperature that would assure a higher tip end and seat hardness combined with lower distortions.