This depends on a lot of factors, e. g. substrate roughness, radius of curvature of a cutting edge to be coated, intrinsic stresses of your coating, egg-shell-effects, and, of course, your coating equipment. The industrial compromise for most substrates is actually 2 - 4 µm which requires typically a pure deposition time (without pumping, heating, etching, cooling, venting, etc.) of 1 - 2 h in an industrial sputter- or arc-coating machine for a full load. The stainless steel should be hardened with sufficiently high tempering temperature before coating for avoiding the before mentioned egg-shell-effect if extrinsic high stresses are applied. Rz/Ra of your substrate should be lower than 1.0/0.1 µm.
It depends on your deposition system, substrate type, applied voltage, and the value coating thickness. However, generally for Arc-PVD coating system the deposition time is lower than magnetron sputtering system. (less than 3 hours in both of them)
it depends upon a factor specially on atmosphere. Optimum deposition time for TiN PVD coating on stainless steel specimen could be 60-150 minute. Generally, sputtering time may be a relevant factor in relation to adhesion, it can be between 60 minutes to 150 minutes. However, increasing time and temperature without changing the sputtering atmosphere may not enough to improve the adhesion either.
