J Fail. Anal. and Preven. (2012)12: 267-272 Kinetic Energy of 45" Impac (45%)impact samples are presented in Fig. 2. As shown in 0.04 Internal Energy of 45'"Impact the curves, the initial kinetic energies of the erodent pa Kinetic Energy of 90 Impact ticles converted into the internal energies of the target Internal Energy of 90 Impact he rebound kinetic energies of the particles. As for ductile target, the internal energy commonly appears in the form of plastic deformation. Thus, based on the fact as shown in 002 Fig. 2 that the internal energy absorbed by target under 90 was higher than that under 45 it can be concluded that greater plastic deformation was induced from normal impact than from oblique impact. This phenomenon has been verified through Fig. 3 as well: larger deformed area 0.00 of the coatings after normal impact than after oblique Impact Figure 4a and b show the interfacial shear stresses dis- Fig 2 Intemal and kinetic energies evolutions under normal and tributions between coating and substrate during impact blique impact The shear stresses of the two samples both reached their 1460 7300 5840 81 t1. Ous Pa)0000 1.0ps 022 = 8760 g760 2921 29 1460 1168 1168 300 5840 t=3.0 Pa)0000 MPa)0000 168 22 4381 t7Ous t=7.Ous P)0000 Fig 3 Stress distribution of the coating:(a) normal impact;(b)oblique impact Spring(45) impact samples are presented in Fig. 2. As shown in the curves, the initial kinetic energies of the erodent par￾ticles converted into the internal energies of the targets and the rebound kinetic energies of the particles. As for ductile target, the internal energy commonly appears in the form of plastic deformation. Thus, based on the fact as shown in Fig. 2 that the internal energy absorbed by target under 90 was higher than that under 45, it can be concluded that greater plastic deformation was induced from normal impact than from oblique impact. This phenomenon has been verified through Fig. 3 as well: larger deformed area of the coatings after normal impact than after oblique impact. Figure 4a and b show the interfacial shear stresses dis￾tributions between coating and substrate during impact. The shear stresses of the two samples both reached their Fig. 3 Stress distribution of the coating: (a) normal impact; (b) oblique impact Fig. 2 Internal and kinetic energies evolutions under normal and oblique impact J Fail. Anal. and Preven. (2012) 12:267–272 269 123