The need to improve the surface properties of materials, has led to the development of parts coated with hard materials deposited on substrates. In this work, by using the finite element method the AA Aluminium 6063 T6 hardness with an error less of the 5 % of the Brinell hardness (HBN), in comparison with the experimental data supplied, was determined. For this, the modelling of a spherical indentation test was carried out, in which the indentation loads and the projected contact radius are obtained from several potential adjustments. Then, using the Lessage-Pertúz model the hardness of the Ni-P coating was determined, obtaining a value of 4.86 GPa.