Properties and Performance Crtialn of Multilayer Hard Coatings Deposited Using Magnetron Sputter Ion Plating

Abstract

A new CrTiAlN coating has been produced using closed field magnetron sputter ion plating and individual Ti, Al and Cr metal targets. M42 high speed steel coupons, 30 × 30 × 3.0 mm stainless steel (316) and 6.35 mm diameter (¼in) high speed steel twist drills were used as substrates. The coating was structured as follows: a Cr rich metal adhesive layer; a monolithic CrN nitride columnar layer with increasing content of Ti and Al; and finally, the nanoscale CrTiAlN multilayer. The composition ratio of Cr, Ti and Al in the multilayer was optimised and the nitrogen flow was controlled using an optical emission monitor with feedback control to produce stoichiometric CrTiAlN (metal/N ~50:50). Some of the as coated samples were heat treated in air at 600°C and 900°C, and then the coating compositions and structures were studied using XRD, GDOES, and TEM with special reference to the effects of the heat treatment. The hardness, adhesion and wear properties of the coating were studied and the properties of the as coated and the heat treated samples were compared. It has been shown that the coatings have many desirable properties (hardness, toughness, wear resistance and thermal stability) at high level. The main part of the coating was formed as a nanoscale multilayer and this coating was applied on to twist tool steel drills giving excellent drilling performance.