In a hard-film-coated drill having a cemented carbide drill body coated with a hard film, the drill body is provided with a smooth region at a boundary between a flank surface and a rake surface. The surface hardness of the hard film is within 2000 to 2500 HV in Vickers hardness. A radius r1 (m) of curvature of the first ridgeline L1 where the smooth region and the flank surface intersect is represented by r1=0.45D+a1 (10a125), where D is the diameter (mm) of the body. A radius r2 (m) of curvature the second ridgeline L2 where the flank surface and a margin intersect is represented by r2=0.65D+a2 (39a267). A thickness t1 (m) of the hard film is represented by t1=0.8ln(D)+a3 (0.7a33.0).

A method for coating a substrate 11 is disclosed. The method includes at least the following steps: depositing a first base layer 22 comprising a nitride of at least Al and Cr on the substrate 11 by physical vapor deposition at a gradually increasing substrate bias voltage from a first substrate bias voltage to a second substrate bias voltage; depositing a second base layer 23 comprising a nitride of at least Al and Cr on the first base layer 22 by physical vapor deposition at a constant substrate bias voltage that is greater or equal to the second substrate bias voltage; and depositing an outermost indicator layer 24 on the second base layer 23, wherein the outermost indicator layer 24 comprises a nitride of Si and Me, wherein Me is at least one of Ti, Zr, Hf, and Cr, wherein the outermost indicator layer 24 is deposited by physical vapor deposition at a substrate bias voltage that is less than the constant substrate bias voltage applied during deposition of the second base layer 23.

In one aspect, a coated cutting tool described herein comprises a substrate and a coating adhered to the substrate, the coating including a refractory layer comprising AlON, the AlON layer exhibiting a peak in a range of 33-35 2 in an XRD, wherein the peak has a FWHM of 0.1-0.7 2. In some embodiments, the AlON layer can exhibit a ribbon-like crystallites, needle-like crystallites, or rice-like crystallites and associated surface texture.