The major difference of the curves is the slope of the unloading curves at the maximum load, which are used for the evaluation. The change of slope at this point is not easily detectable by bare eye. The offset on the y-axis is mainly caused by hardness differences of the coating, not the modulus. The results of the inverse procedure and of the Oliver & Pharr method for the coating modulus normal to the coating surface are shown in Fig. 14.