Structure, Morphology, and Mechanical Properties of AlCrN Coatings Deposited by Cathodic Arc Evaporation
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Structure, Morphology, and Mechanical Properties of AlCrN Coatings Deposited by Cathodic Arc Evaporation Adam Gilewicz, Roman Jedrzejewski, Piotr Myslinski, and Bogdan Warcholinski (Submitted July 30, 2018; in revised form December 12, 2018) AlCrN coatings were deposited on steel substrates (HS6-5-2) using cathodic arc evaporation. The effect of nitrogen pressure on the properties of CrAlN coatings formed from Al80Cr20 cathode, such as chemical and phase composition of the coatings, surface morphology, deposition rate, hardness and adhesion to the substrate, and friction and wear were investigated. The coating deposited at nitrogen pressure of 3 Pa shows the highest deposition rate. The roughness parameter Ra of the coating surface decreases with increasing nitrogen pressure during its formation. The test results showed that the AlCrN coatings deposited under nitrogen pressure in the range from 1 to 5 Pa show similar hardness for all the coatings, which is around 17 GPa. The increase in the negative bias voltage of the substrate during the formation of the coating deteriorates its adhesion to the substrate, although the wear rate is rather good, about 1.4 3 1027 mm3/Nm. The coatings deposited at nitrogen pressure of 3-4 Pa are characterized by the highest critical load, 95 N. Despite worse adhesion, these coatings are characterized by high resistance to wear, the wear rate is about 1.4 3 1027 mm3/Nm. Keywords
adhesion, AlCrN, hardness, morphology, structure
1. Introduction Chromium nitride coatings are used extensively in metalworking due to its good mechanical and tribological properties as well as corrosion resistance (Ref 1-5). The industry requirements related to the increase in efficiency and speed of machining processes make the problem of durability and reliability of cutting tools extremely important. Not all coating materials meet these requirements. CrN is applied to protect cutting tools, but their hardness and oxidation resistance are not always enough to meet the requirement of modern mechanical machining. There are different ways to improve mechanical and tribological properties of the coatings. One of the methods is addition of metallic or non-metal elements such as Ti, Si, Ta, Al, Nb, C, B to CrN. It is known that better coating properties are strongly associated with its unique microstructure. One of the most promising ternary systems is Al-Cr-N. AlCrN is particularly attractive due to their excellent resistance to oxidation and mechanical properties as well as chemical stability (Ref 6). AlCrN has better wear resistance due to the formation of permanent oxide layers on the worn surfaces. Adding aluminum to CrN increases wear resistance at high temperatures (Ref 7). AlCrN coatings show very high hardness at elevated temperatures and resistance to wear under extreme mechanical stress. The properties depend on the aluminum Adam Gilewicz, Piotr Myslinski, and Bogdan Warcholinski, Faculty of Technology and Education, Koszalin University of Technology, Koszalin, Poland;
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