Design, synthesis and characterisation of multilayered PVD coatings

Sammanfattning: Physically vapour deposited multilayered coatings were the target of this thesis.Several different wear resistant nitride coatings (TiN/CrN, TiN/MoN, TiN/NbN andTiN/TaN) have been evaluated. Investigations correlating fundamental coatingcharacteristics such as microstructure, chemical and phase composition to themechanical, tribological and corrosion behaviour have been performed. Furthermore,TiN/TaN coated tools have been evaluated in milling of austenitic stainless steel.Of the two different deposition systems utilised, the most frequently usedcombines reactive electron beam evaporation and reactive magnetron sputtering. Thissystem enables growth of well adhering coatings with a large variety of tribologicalproperties. The second one is a dual-target sputter system equipped with shutters overthe two targets. In this system, growth of coatings with very well defined lamellathickness can be obtained by using shutters. This also enables variation of thechemical composition of only one lamella material at a time.From the present work, it was concluded that TiN/CrN is a coating with overallgood properties, combining high toughness, low residual stress and high wearresistance. A coating with very thin lamellae of TiN and CrN obtain both good wearand corrosion resistance.A multilayered TiN/TaN coating is an excellent choice when a high wearresistance, abrasive as well as erosive, is required. This coating has also shown verypromising results in milling of austenitic stainless steel. Furthermore, it has beenshown that the residual stress in TiN/TaN can be varied within a very broad range bychanging the nitrogen partial pressure during deposition. This coating has shown topossess a very high tensile fracture strength, as compared to most ceramic materials.A new hydrocarbon free PVD process has been developed and used to depositTi-C coatings. This coating provides a low friction and very good sliding wearresistance. Hence, this coating may be suitable for machine elements.In addition to synthesis of a number of new PVD coatings, a new tool forevaluation of the intrinsic mechanical properties of multilayered coatings has beensuggested. The tool allows detection of too large residual stress mismatch and/or badinterlamella adhesion in such coatings.