Performance of gas nitrided and AlTiN coated AISI H13 hot work tool steel in aluminium extrusion

► The compound layer of the nitrided steel spalls off the surface during sliding wear. ► The underlying brittle diffusion zone remains unprotected and suffers fracture. ► Spallation follows and produces wear craters on the surface of the nitrided sample. ► AlTiN resists delamination and protects the underlying steel substrate. ► Wear rates are 5.2 × 10− 9 and 4.0 × 10− 12 mm3 N− 1 m− 1 for the nitrided and coated samples, respectively.