Nanocrystalline TiN has been imbedded in amorphous silicon nitride matrix to form a super hard nanocomposite thin film (nc-TiN/a-SiNx) via magnetron sputtering. Adjusting Ti and Si3N4 target power ratio altered film composition, size, amount and distribution of the nc-TiN phase. At a Ti target power density of 5.5 W cm−2, the Ti to Si3N4 target power ratio should be greater than unity in order for nc-TiN to form, otherwise, Ti will dissolve in amorphous SiNx. The relationship between the film hardness and the crystallite size show Hall–Petch and anti-Hall–Petch relationship. A ‘scratch crack propagation resistance’ parameter, or CPRs=Lc1(Lc2−Lc1), has been proposed to approximate thin film toughness from the critical load data easily obtained from a scratch adhesion test.