Properties Of TiAlN And TiAlSiN Coatings On Die Steels Deposited By HiPIMS

Die is the key factor of industrial development.With the rapid development of modern manufacturing industry,the working conditions of cold work die steel and hot work die steel become worse and worse,which puts forward more stringent requirements for all aspects of die properties.Die damage mainly occurs on the surface,which affects the service life of the die and reduces the industrial production efficiency.Surface modification by physical vapor deposition(PVD)is an effective way to improve the performance of substrates,which has been widely used in cemented carbide tools and other substrates.There are few researches on using PVD technology to deposit hard nitride coatings on die surface.In this paper,TiAlN and TiAlSiN coatings were deposited on H13,3Cr2W8V and Cr12MoV die steels by high power impulse magnetron sputtering(HiPIMS).This paper mainly studied the effects of TiAlN and TiAlSiN coatings on the corrosion resistance,wear resistance of cold working die steels and high temperature oxidation resistance of hot working die steels.The main results are as follows:(1)TiAlN and TiAlSiN coatings deposited by high power impulse magnetron sputtering had no obvious holes,cracks and delamination.There was element diffusion between the coatings and the substrates,and the coatings were compact.Due to the bombardment of high energy particles,the surface had a certain roughness.The addition of Sielement in TiAlSiN coating reduced the columnar crystal structure and refined the grain size,which further improved the hardness of the substrates.The surface quality and adhesion of the coatings were affected by the substrates.When hardness of the substrate was high and the physical properties matched the coating,the coating showed higher hardness and better adhesion.(2)The corrosion behavior of cold working die steel Cr12MoV in electrochemical corrosion and cavitation corrosion was studied.Compared with the substrate,TiAlN coating and TiAlSiN coating significantly reduced the corrosion rate of the substrate in the electrochemical corrosion process,and the corrosion mechanism was mainly pitting corrosion.The coating reduced the probability of corrosive medium entering into the coating and contacting with the substrate,which played a barrier role and improved the corrosion resistance of the substrate.TiAlSiN coating had the lightest degree of cavitation in the process of cavitation,and the high hardness of TiAlSiN coating can effectively resist the impact of cavitation and the effect of micro jet.The results shows that TiAlN coating with Sielement can effectively inhibit the crack initiation and propagation,prevent the connection of cavitation pits,and prevent the coating from spalling failure in large area.(3)The main wear forms of the substrate were abrasive wear and adhesive wear,while the coatings were abrasive wear and fatigue wear.High hardness of TiAlN and TiAlSiN coatings reduced the friction coefficient of the substrate.The TiAlSiN coating had higher hardness than the TiAlN coating and therefore the TiAlSiN coating had lowest friction coefficient.The amorphous Si₃N₄ coated TiAlN nanocomposite structure makes the grain boundary sliding difficult and improves the wear resistance.(4)The dense oxide layer forms in the oxidation process of TiAlN coating and TiAlSiN coating can effectively reduce the weight gain rate and increase the oxidation resistance temperature of the substrate.TiAlN coating was completely oxidized at 950?,while TiAlSiN coating still had partial protection.The joint action of Al₂O₃ and SiO₂ in TiAlSiN further blocks the diffusion of oxygen into the coating.The fine grains and dense coating structure reduce the diffusion rate of oxygen,which plays an effective role in preventing oxygen and improving the high temperature oxidation resistance of the substrate.