Magnetron sputtering: a review of recent developments and applications

We review the status of (Ti,Al)N based coatings obtained by various physical vapor deposition (PVD) techniques and compare their properties. PVD techniques based on sputtering and cathodic arc methods are widely used to deposit wear resistant (Ti,Al)N coatings. These techniques were further modified to improve the metal ionization rate and to eliminate macrodroplets from plasma streams. We summarize manufacture of target/cathode, substrate materials for deposition of coatings, deposition parameters, and the effect of deposition parameters on the physical and mechanical properties of (Ti,Al)N coatings. It is shown that (Ti,Al)N coatings by PVD enhance the wear, thermal, and oxidation resistance of a wide variety of tool materials. We discuss the wear resistant properties of (Ti,Al)N for various machining applications as compared with coatings such as TiN, Ti(C,N) and (Ti,Zr)N. High hardness (∼28–32 GPa), relatively low residual stress (∼5 GPa), superior oxidation resistance, high hot hardness, and low thermal conductivity make (Ti,Al)N coatings most desirable in dry machining and machining of abrasive alloys at high speeds. Multicomponent coatings based on different metallic and nonmetallic elements combine the benefit of individual components leading to a further refinement of coating properties. Alloying additions such as Cr and Y drastically improve the oxidation resistance, Zr and V improve the wear resistance, whereas, Si increases the hardness and resistance to chemical reactivity of the film. Addition of boron improves the abrasive wear behavior of Ti–Al based coatings due to the formation of TiB2 and BN phases depending on the deposition conditions. Hafnium based nitrides and carbides have potential for resistance to flank and crater wear. The presence of a large number of interfaces between individual layers of a multilayered structure results in a drastic increase in hardness and strength. (Ti,Al)N multilayer super lattice coatings with lattice periodicity of 5–10 nm allow creation of coatings with different properties than PVD deposited single layered thick coatings with columnar grain structure. A range of (Ti,Al)N based multilayers containing layers of (Ti,Al)CN, (Ti,Nb)N, TiN, AlN/TiN, CrN, Mo and WC are also reviewed. It is now possible to design new wear resistant or functional coatings based on a multilayer or a multicomponent system to meet the demanding applications of advanced materials.

Single layer and multilayer wear resistant coatings of (Ti,Al)N: a review

This updated version of the popular handbook further explains all aspects of physical vapor deposition (PVD) process technology from the characterizing and preparing the substrate material, through deposition processing and film characterization, to post-deposition processing. The emphasis of the new edition remains on the aspects of the process flow that are critical to economical deposition of films that can meet the required performance specifications, with additional information to support the original material. The book covers subjects seldom treated in the literature: substrate characterization, adhesion, cleaning and the processing. The book also covers the widely discussed subjects of vacuum technology and the fundamentals of individual deposition processes. However, the author uniquely relates these topics to the practical issues that arise in PVD processing, such as contamination control and film growth effects, which are also rarely discussed in the literature. In bringing these subjects together in one book, the reader can understand the interrelationship between various aspects of the film deposition processing and the resulting film properties. The author draws upon his long experience with developing PVD processes and troubleshooting the processes in the manufacturing environment, to provide useful hints for not only avoiding problems, but also for solving problems when they arise. He uses actual experiences, called 'war stories', to emphasize certain points. Special formatting of the text allows a reader who is already knowledgeable in the subject to scan through a section and find discussions that are of particular interest. The author has tried to make the subject index as useful as possible so that the reader can rapidly go to sections of particular interest. Extensive references allow the reader to pursue subjects in greater detail if desired. The book is intended to be both an introduction for those who are new to the field and a valuable resource to those already in the field. The discussion of transferring technology between R&D and manufacturing provided in Appendix 1, will be of special interest to the manager or engineer responsible for moving a PVD product and process from R&D into production. Appendix 2 has an extensive listing of periodical publications and professional societies that relate to PVD processing. The extensive Glossary of Terms and Acronyms provided in Appendix 3 will be of particular use to students and to those not fully conversant with the terminology of PVD processing or with the English language. This title is fully revised and updated to include the latest developments in PVD process technology. It includes 'War stories' drawn from the author's extensive experience emphasize important points in development and manufacturing. Appendices include listings of periodicals and professional societies, terms and acronyms, and material on transferring technology between R&D and manufacturing.

Handbook of physical vapor deposition (PVD) processing

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulse ...

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High power impulse magnetron sputtering discharge

In recent years, several new solid lubricant and modern lubrication concepts have been developed to achieve better lubricity and longer wear life in demanding tribological applications. Most of the traditional solid lubricants were prepared in the form of metal, ceramic and polymer-matrix composites. They have been used successfully in various engineering applications. Recent progress in thin-film deposition technologies has led to the synthesis of new generations of adaptative, self-lubricating coatings with composite or multilayered architectures, by using duplex/multiplex surface treatments. These modern self-lubricating coatings progressively make their way into the commercial marketplace and meet the ever-increasing performance demands of more severe applications. The present paper reviews our recent understanding of the lubrication mechanisms of both traditional and new solid lubricants, with particular emphasis on solid lubricant methods and practices.

Historical developments and new trends in tribological and solid lubricant coatings.

Attention is given to an opposed cathode sputtering system constructed with the ability to coat parts with a size up to 15 cm in diameter and 30 cm in length. Initial trials with this system revealed very low substrate bias currents. When the AlNiCo magnets in the two opposed cathodes were arranged in a mirrored configuration, the plasma density at the substrate was low, and the substrate bias current density was less than 1 mA/sq cm. If the magnets were arranged in a closed-field configuration where the field lines from one set of magnets were coupled with the other set, the substrate bias current density was as high as 5.7 mA/sq cm when NdFeB magnets were used. In the closed-field configuration, the substrate bias current density was related to the magnetic field strength between the two cathodes and to the sputtering pressure. Hard well-adhered TiN coatings were reactively sputtered in the opposed cathode system in the closed-field configuration, but the mirrored configuration produced films with poor adhesion because of etching problems and low plasma density at the substrate.

High rate reactive sputtering in an opposed cathode closed-field unbalanced magnetron sputtering system

The effect of target power on the nitrogen partial pressure level and hardness of reactively sputtered titanium nitride coatings

The N 2 partial pressure, target power and substrate bias potential all have a significant effect on the hardness and crystallographic orientation of TiN coatings prepared by high-rate reactive sputtering on cemented carbide substrates Variations in both the substrate bias potential and the target power had a strong affect on the hardness and texture of the TiN coatings Vickers microhardness values (50gf) of the TiN coatings varied between 970 and 3290 kgf mm -2 as the bias was stepped between 0 and –200 V and the target power between 23 and 100kW The texture coefficient of the TiN coatings with a constant –100 V bias was strongly (111) at the low power level of 23 kW, but the texture became random as the power was increased to 40 kW and above with the same –100 V bias At a fixed power level of 10 kW, the orientation of the TiN coatings changed from (111) at zero bias to (200) between –20 and –100 V, to strongly (220) at –150 and –200 V The hardness of TiN coatings with N/Ti ratios of 070 - 101 produced by varying the N 2 partial pressure during deposition had a narrow range between 3140 and 3400 kgf mm -2 , but the texture coefficient varied from random to strongly (220) the adhesion of the TiN coatings was measured with the scratch test, and a critical load of 80 ± 05 kgf was the same for all samples except for the ones at the lowest target power (23 kW), low biases (0 and –20 V) and the lowest N/Ti ratio (070)

The effect of N2 partial pressure, deposition rate and substrate bias potential on the hardness and texture of reactively sputtered TiN coatings

Summary High-rate reactive sputtering (HRRS) requires rapid and careful control of the reactive gas partial pressure to achieve high deposition rates and to maintain stoichiometry in the coating. HRRS of TiN was first achieved with feedback control of the N 2 utilizing a differentially pumped mass spectrometer system to sense the N 2 partial pressure. Recently, a new instrument called the optical gas controller (OGC) that operates at sputtering pressures became available for sensing the partial pressure of the gases in the sputtering atmosphere. The OGC was used during the reactive sputtering of TiO x with partial-pressure control, and the TiO x hysteresis loop exhibited a wide negative slope region which is much larger than the one found during the reactive sputtering of TiN x . Partial-pressure control, compared to mass flow control during oxide reactive sputtering, leads to better control of the process and to a 3.5 times higher deposition rate for highly resistive oxide coatings. With partial-pressure control, the anatase form of TiO 2 has been produced with lattice parameters of a 0 = 3.780 A and c 0 = 9.610 A.

Advances in partial-pressure control applied to reactive sputtering

Reactive unbalanced magnetron sputtering was used to deposit eight different nitride coatings on hardened 440C stainless steel rolling contact fatigue (RCF) test specimens. The target materials used in this study were Ti, Zr, Hf, Cr, Mo, Ti0.5Al0.5, Ti0.5Zr0.5 and Ti-Al-V (the aircraft alloy Ti-6 wt.%Al-4wt.%V). All the coatings were characterized using X-ray diffraction, microhardness and scratch adhesion tests. Ti, Zr and Hf form the simple binary nitrides of TiN, ZrN and HfN, respectively, with an f.c.c. structure and a range in stoichiometry. Cr and Mo form a range of nitrides, starting with a solid solution of nitrogen in each of them, a Cr2N or Mo2N phase, and a CrN or MoN phase. The MoN phase was not conclusively formed in this work. Mo2N forms in two different phases, i.e. β and γ phases, depending on the nitrogen partial pressure. The Ti-alloyed nitrides all form an f.c.c. structure. The coatings selected for the RCF tests ranged in hardness from a low of 1900 kg mm−2 for Ti0.5Al0.5N and CrN to a high of 2800 kg mm−2 for Ti0.5Zr0.5N. The deposition conditions for forming these nitrides are given in this paper. Also, the similarities and differences, both in the deposition conditions and in the resulting properties, are reviewed.

P.J. Rudnik

Papers

High rate reactive sputtering in an opposed cathode closed-field unbalanced magnetron sputtering system

The effect of target power on the nitrogen partial pressure level and hardness of reactively sputtered titanium nitride coatings

The effect of N2 partial pressure, deposition rate and substrate bias potential on the hardness and texture of reactively sputtered TiN coatings

Advances in partial-pressure control applied to reactive sputtering

Reactive unbalanced magnetron sputtering of the nitrides of Ti, Zr, Hf, Cr, Mo, Ti-Al, Ti-Zr and Ti-Al-V