The Preparation Of Multi-component Nitride Coatings And Cutting Performance For High-speed Dry Milling

With the development of society and technology, difficult-to-cut materials have been widely used in the advanced manufacturing technology, marine technology, space technology and nuclear technology. This proposes the higher demand of the performance to the sophisticated mechanical equipment and the cutting tools for manufacturing the difficult-to-cut materials. Hardened steel, one of the typical difficult-to-cut materials, is commonly used in the manufacture of key components which need higher hardness and wear resistance due to its high hardness and strength. Accordingly, How to effectively solve the problem of machining hardened steel has been an important research topic. Compared with the traditional processing methods, high-speed cutting cutting (HSC) method hardened steel shows a higher efficiency, better finished surface and lower processing costs. In addtion, the coating technology played a critical role in cutting tools. The coatings with excellent properties can significantly improve the cutting performance and increase the tool life.In this paper, CrTiAIN coating, AlCrN coating and AlCrTiSiN coating were prepared on cutting tools for high speed milling hardened steel using unbalanced magnetron sputtering system and multi-arc ion plating system respectively. The coating performance were measured by using modern materials analysis techniques. The coating/substrate adhesive strengths, the friction coefficients, hardnesses, micro structures and compositions of the as-deposited coatings were chareacterized carefully. The results show that the as-deposited coatings have a high hardness, good adhesion, low friction coefficient etc.Cutting experiments were carried out with optimized programs for high-speed milling hardened steel under dry cutting condition. The cutting performances and adaptabilities of the coated cemented carbide end mills for different hardened steels were studied by measuring the tool wear, wear morphologies and curing force directly. Combining the results of the cutting tests and the metal cutting theory, wear and breakage mechanism were discussed during the metal cutting process. Analysis model of the curing tribology and evaluation method of the cutting tools wear failure were established. The results show that the as-deposited coating can diminish the mechanical stress among tool and chips, and make the chips run out easily. And the cutting forces and flank wear of the coated tools were decreased efficiently compared with that of the tools withous coatings. The dimensional accuracy and quality of the whole machining process were improved sharply. The chemical composition and surface morphology of the flank edge of the end mills were analyzed using SEM and EDX. It was found that the initial wear stage of the coated tool was shorter, but the normal wear stage was prolonged. It is clearly that the coatings decreased the wear of the cutting tool and thus improved the life of the cutting tools. The wear mechnisms of coated cutting tools mainly are flank wear and abrasive wear, accompany with adhesive wear, oxidation wear and breakage of the tool tip/cutting edge.