Material characterization Mechanical characteristics Ductile materials failure due to plastic deformation because of dislocation slip. Brittle materials failure due to crack propagation enhanced by stress concentration. H/E surface resistance to sliding wear (significant in abrasive and erosive wear). H3/E2 resistance to the onset of plastic deformation. not significant for ceramics (Hα) H/K index of brittleness

Elasto-plastic properties Hardness (H)= applied load(P)/ projected contact area(A) (units Pa or Gpa) Hard ceramic materials vickers tip geometry DSI(depth sensing indentation) contact pressure at maximum load is measured where the deformation is elastic and plastic. Static indentation tests deformation is only plastic but elastic component is being neglected. W total =W plastic +W elastic index of plasticity Rp=1-Re where Re energy recovered after complete unloading all these properties are determined using indentation tests Rp α H/E substrate effect is dominant in very thin films