The effect of nitrogen vacancies on initial wear in arc deposited (Ti^sub 0.52^,Al^sub 0.48^)N^sub y^, (y < 1) coatings during machining

Nitrogen deficient c-(Ti0.52Al0.48)Ny, y = 0.92, y = 0.87, and y = 0.75 coatings were prepared in different N2/Ar discharges on WC-Co inserts by reactive cathodic arc deposition. The microstructure of the y = 0.92 coating show that spinodal decomposition has occurred resulting in the formation of co...

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Bibliographic Details
Published in:Surface & coatings technology 2019-01, Vol.358, p.452
Main Authors: Calamba, KM, Jõesaar, MP Johansson, Bruyère, S, Pierson, JF, Boyd, R, Andersson, JM, Odén, M
Format: Article
Language:English
Subjects:
Age hardening
Aging (artificial)
Aluminum
Arc deposition
Cathodic coating (process)
Cemented carbides
Cobalt
Cutting
Decomposition
Dislocations
Domains
Electric arcs
Free energy
Grain boundaries
Inserts
Lattice vacancies
Machining
Macroparticles
Microstructure
Misfit dislocations
Nitrogen
Organic chemistry
Precipitation hardening
Protective coatings
Spinodal decomposition
Substrates
Wear resistance
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Summary:Nitrogen deficient c-(Ti0.52Al0.48)Ny, y = 0.92, y = 0.87, and y = 0.75 coatings were prepared in different N2/Ar discharges on WC-Co inserts by reactive cathodic arc deposition. The microstructure of the y = 0.92 coating show that spinodal decomposition has occurred resulting in the formation of coherent c-TiN- and c-AlN rich domains during cutting. The y = 0.87 and y = 0.75 coatings have exhibited a delay in decomposition due to the presence of nitrogen vacancies that lowers the free energy of the system. In the decomposed structure, grain boundaries and misfit dislocations enhance the diffusion of elements from the workpiece and the substrate (e.g. Fe, Cr, and Co) into the coatings and it becomes more susceptible to crater wear. The y = 0.87 sample displays the highest crater wear resistance because of its dense grain boundaries that prevent chemical wear. The y = 0.92 sample has the best flank wear resistance because the decomposition results in age hardening. The y = 0.75 sample contains the MAX-phase Ti2AlN after cutting. The chemical alteration within the y = 0.75 sample and its high amount of macroparticles cause its low wear resistance. The different microstructure evolution caused by different amount of N-vacancies result in distinctive interactions between chip and coating, which also causes difference in the initial wear mechanism of the (Ti,Al)Ny coatings.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2018.11.062