Boundary lubricated wear tests of Nicomet bronze indicates an unusual phenomenon, previously unseen. At a given speed, if the load is increased, the bearing actually, wears less and the system operating temperature decreases. Some explanations of this interesting property are:

 

• Bearing asperities break off and stress is lowered due to increased contact area.

• Work hardening takes place on the bearing surface.

• Some elastic interaction in the spinodal structure begins to operate at high loads.

 

No other bearing alloy will duplicate this behavior. Since the strength of this alloys comes from its composition and heat treatment, it is possible to make very large parts, with high strength, that cannot be extruded, forged or cold worked. The precipitates or hard phases in the other copper alloys represent areas where fatigue cracks will initiate. This limits their ability to withstand cycles of bending or torsion loading. The single phase spinodal bronze is superior to those alloys in fracture toughness.

 

Another attractive property of spinodal bronze is its corrosion resistance. The tin and nickel content of this alloy makes it suitable for marine applications as well as the corrosive environments encountered in oil and gas well drilling.

 

The reason behind the excellent physical properties of spinodal alloys was discovered only after the invention of the electron microscope. Being able to view the microstructure at 100,000 magnifications revealed a layered texture, the layers only being several atoms in thickness. This structure is obtainable as a result of aging after solution treating to cause what is called spinodal decomposition. The layers of slightly different composition come from a movement of the solute atoms during the aging process. This small difference is not a large-scale diffusion to form precipitates which is the normal strengthening action in precipitation hardening alloys. Spinodal decomposition is possible when all the different metal atoms are nearly the same size and can form a completely homogeneous solid solution.

 

Since some spinodal alloys may actually create precipitates upon slow cooling from the solid solution, it may be necessary to quench those metals from the solid solution temperature. The desired atomic shift can then be affected by aging at a lower temperature to allow the crystals to strengthen by atoms of one kind to move to areas of higher concentration without forming a precipitate.

 

The unique Nicomet spinodal bronze properties suggest applications in hydraulic pump cylinder heads (no need for cylinder sleeves), heavy vehicle bearings, wear plates for stamping presses and many other applications. ​NICOMET® Spinodal Bronze presents new possibilities to equipment designers when a combination of high impact strength, fatigue resistance, toughness, low wear and corrosion resistance is required.​​

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Properties & Benefits

• High Strength and Hardness: Spinodal bronze has high tensile strength, yield strength, and hardness, making it suitable for demanding applications.

• Superior Wear Resistance: Wear tests have shown it wears at less than half the rate of beryllium copper and aluminum bronze. In fact, at high loads, it can actually wear less due to a unique low-friction film that forms on mating steel parts.

• Excellent Corrosion Resistance: The alloy provides high resistance to corrosion, including in harsh environments like oil and gas drilling.

• Non-Magnetic and Lead-Free: It is non-magnetic and, unlike some traditional bronzes, can be lead-free, making it an environmentally friendly option.

• Toughness and Fatigue Resistance: The material is known for its high impact strength, toughness, and fatigue resistance.

• Dimensional Stability: Because spinodal decomposition does not involve a change in crystal structure, the alloy maintains excellent dimensional stability during the hardening process. 

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Manufacturing Process

The unique properties of spinodal bronze are a result of a specific heat treatment cycle: 

1. Homogenization: The alloy is heated to a high temperature to form a single, homogeneous solid solution.

2. Quenching: It is then rapidly cooled (often with brine for maximum effectiveness) to room temperature to "freeze" the homogeneous state.

3. Aging: Finally, the alloy is reheated to a lower temperature within the spinodal region. This triggers spontaneous, nanoscale chemical separation (spinodal decomposition) that creates a fine, ordered atomic structure, significantly enhancing strength and hardness. 

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Common Applications

Spinodal bronze is used in critical components across various industries due to its robust properties: 

• Aerospace: Landing gear bearings, guide plates, and other aircraft parts.

• Automotive and Heavy Equipment: Valve guides, roller bearing cages, bushings, and thrust washers.

• Oil & Gas: Drilling equipment, pressure housings, and other hardware that requires high strength and corrosion resistance.

• Electrical: High-performance electrical connector parts, spring contacts, and circuit breaker parts.

• Industrial Machinery: Heavily loaded bearings, bushings, wear plates, gears, and pump parts.