Nickel alloy maintains a balance in the composition of other alloying elements so as to obtain optimum properties. Both the alloys are solid solution strengthened, and hence the strength of both the pure metals is exceptional. Both the grades have similar chemical composition except for their carbon content.
Hence, grade 201 is used for applications at elevated temperatures since its lower carbon content will restrict embrittlement due to graphitization or carbide precipitation. In the range of 430- 650°C, the use of Nickel 200 is not recommended since it might lose its ductility due to the carbide precipitation. In annealed condition, they have an approximate strength of mild steel, while in rolled condition, they have better strength. Both the grades are ferromagnetic by nature. The specific properties of Nickel 200 include high thermal as well as electrical conductivity, low gaseous constituents, low electrical resistivity and appropriate magnetic properties.
The thermal conductivity of Nickel 200 is 487 Btu.in/ft^2. h.°F (British thermal unit). The torsional strength of the grade in breaking strength of 1” dia rod is 558 MPa, which is quite competent. Hence it could be used in dynamic applications as required. The grade is one of the toughest in respect to impact strength properties due to its nickel content. During Izod test, the alloy can absorb 163J of energy and during Charpy v-notch test it can absorb 271J in impact. As per Charpy tests, Nickel 200 stands as the most durable alloys in regards to impact properties. The grade also has brilliant properties in stress fatigue cycles.
The grade in cold worked condition will endure 10^6 cycles in fresh water with 386MPa maximum stress, in seawater, it will be 372 MPa, and in air, it will be 434MPa. The grade 200 forms a protective passive layer in the presence of oxidizing environment, hence is used in respective applications. The resistance to caustics by the grade is due to the presence of this layer. The Nickel grade 201 has a lower work hardening rate and is suitably used for cold-working operations. Both the grades can be considerably hot formed to almost every shape with proper end temperature. The strength of the grade can be significantly increased with cold-working processes.
