Rockwell　C　diamond　indenter　with　a　spherical　tip　of　radius　of　108　mu　m　was　used　to　slide　on　bulk　polycarbonate　under　linearly　increasing　normal　load　from　5　mN　to　20　N　in　order　to　investigate　deformation　and　damage　of　ductile　polymers　during　scratching.　The　peak　value　of　the　ratio　of　residual　depth　over　penetration　depth　corresponds　to　a　critical　normal　load,　which　can　be　used　as　the　piecewise　point　for　the　subsection　functions　describing　variation　of　tangential　load,　penetration　depth　and　residual　depth　with　normal　load.　The　true　adhesion　interfacial　friction　coefficient　was　found　to　be　0.3　for　contact　between　PC　and　diamond　by　three-dimensional　model.　Residual　groove　widths　were　found　to　be　proportional　to　the　square　root　of　normal　load,　and　provided　useful　information　to　characterize　the　radius　of　spherical　tip.　Values　of　fracture　toughness　of　PC　obtained　by　scratch-based　methodologies　under　sufficiently　large　normal　loads　associated　with　brittle　fracture　and　crack　plane,　are　in　excellent　agreement　with　literature　values.　The　material　is　under　triaxial　compressive　stress　state,　making　the　flow　and　shear　stresses　much　larger　than　the　ones　for　uniaxial　tensile　test.