Mechanical property degradation due to ordering phase transformation is of potential concern for alloys based on the Ni-Cr binary system (e.g., 690, 625), particularly in nuclear power applications where component lifetimes can exceed 40 years. In the present research, the disorder-order phase transformation has been studied in Ni-Cr model alloys with varying stoichiometry (30-40 at.% Cr) by a combined experimental and computational approach. Density functional theory-based Kinetic Monte Carlo simulations are used to study both the thermodynamic and kinetic aspects of the phase transformation as a function of Cr concentration. Samples are isothermally aged up to 5,000 hours at four different aging temperatures. Ordering is characterized by changes in lattice parameter via X-ray Diffraction, micro-hardness and by diffraction patterns observed via transmission electron microscopy. The experimental data is used to assess the model accuracy as a function of aging time and temperature.