POLIDUR
X2 NiCoMo18-16.5-5

*Unified Numbering System (USA)

Characteristics and main uses

High elastic limit alloy, very resistant, allowing the production of spring parts. A very high quality polished surface can be obtained with this alloy compared to YAG 250RL and RODUR. This is thanks to the absence of titanium in the chemical composition.

• Superior formability and extremely high mechanical properties after aging, thanks to intensive precipitation with moderate temperature hardening heat treatment. This treatment can be done after shaping because it causes very little dimensional change.
• No weakening at low temperature.
• Excellent resistance to fatigue.
• Structural stability after aging.
• Low thermoelastic coefficient.
• Excellent weldability. The post-weld hardening treatment significantly reduces the differences in properties between welded and non-welded areas, thereby eliminating weak spots.
• No TiN => better properties for polishing

Main uses

PHYTIME® is specially designed for all applications requiring high resistance to fatigue, such as those used in the automotive industry:

• Belt for automatic gearbox
• Cable connectors to motors
• Springs
• Automotive, injection
• Watchmaking

1 poor | 2 average | 3 good | 4 very good | - no info

Comments on heat treatments

Durcissement par vieillissement de la martensite

Heat treatment condition

• The standard hardening treatment is 3 hours at 480°C. This treatment causes the precipitation of intermetallic compounds. This precipitation treatment can be combined with work-hardening.
• Although treatment in air does not impair the material’s properties, it does spoil its appearance, with the metal taking on a blue hue. For this reason, we recommend treating under deep vacuum in the order of 10-5 Torr or under inert atmosphere such as argon.
• Certain atmospheres regarded as inert due to the absence of colouration are in reality chemically active and thus may cause the material to become extremely brittle. This is particularly true in the case of hydrogen and cracked ammonia.
• Influence of service temperature.
•  Following tempering, the tensile and yield strengths of this alloy decreases slower with temperature than those of traditional “piano wire” type spring steels or 18-8 stainless steels his is due to dislocation locking by the precipitates formed during the temper hardening treatment. Variations in the modulus of elasticity (Young’s modulus) as a function of temperature