Physical Vapor Deposition Hard Coatings Research Articles

Investigations of mechanical and tribological properties of CrAlN+C thin coatings deposited on cutting tools

Physical vapor deposition (PVD) of hard coatings such as titanium nitride have been used in industry reality since the beginning of the 1980s. Two processes, Arc-Ion plating (AIP) and Magnetron-sputtering-ion plating (MSIP), were responsible for the early commercial success of hard coatings on high speed steel tooling. There are many similarities and differences between these two PVD hard coating processes, but not all of the commonly used PVD hard coatings can be well deposited with the two systems. In this paper, CrAlN+C thin coatings were deposited on cutting tools materials using a new Physical Vapour Deposition (PVD) hybrid process. The hybrid process is a combination of random Arc-Ion-Plating (AIP) and balanced Magnetron-Sputter-Ion-Plating (MSIP) process, where both processes work simultaneously. The cutting tools should possess the following mechanical and tribological properties: hardness, adhesion, low coefficient of friction and good bond strength between coating and substrate. Coatings that were deposited with the PVD hybrid process showed the required properties for cutting tools. From the machining test results (made from the IPT Institute in Dresden) we can conclude that the CrAlN+C/C coatings can be applied in machining industry. The present work was an advanced AIF-project.

Physical vapor deposition tool coatings

Physical vapor deposition (PVD) of hard coatings such as titanium nitride have been an industrial reality since the beginning of the 1980s. Two PVD processes, low voltage electron beam and cathodic arc deposition, were responsible for the early commercial success of hard coatings on high speed steel tooling. Since that time, two other PVD processes have also been prosperous in the industrial world—high voltage triode electron beam and unbalanced magnetron sputtering. There are many similarities and differences between these four PVD hard coating processes, but not all of the commonly used PVD hard coatings can be deposited well in the four systems. Titanium nitride and titanium carbonitride are the two most widely used PVD tool coatings, and they can be deposited in all four PVD systems. Titanium aluminum nitride can be deposited easily with the unbalanced magnetron process and also with the cathodic arc processes as long as cast targets are used. Uniform composition cannot be maintained with the electron beam processes because of the different vapor pressures of titanium and aluminum. New PVD hard coatings are being developed and applied. Diamond-like carbon is now being tried for some non-ferrous cutting applications, and metal-carbon films are showing promise. Polycrystalline nitride superlattice coatings made of thin alternating layers of two hard coatings such as titanium nitride and niobium nitride are showing potential for abrasive cutting situations because of the very high hardness (up to 5200 HV) of these coatings. The search continues for potentially even better tool coatings. An intense effort is underway to produce the superhard crystalline carbon nitride, which is predicted to have a hardness as hard or even harder than diamond. Similarly, cubic boron nitride (CBN) coatings are still very much in the development stage. Thin CBN coatings can now be deposited up to approximately 2000 Å in thickness, but stress in the films prevents thicker films from being made. Aluminum oxide, which has been very difficult to make by PVD techniques, except in the very slow r.f. sputtering mode, can now be deposited in the d.c. magnetron mode when pulsed power is used.

Surface effects on the growth, adhesion and properties of reactively deposited hard coatings

Atomistic deposition processes such as physical vapor deposition (PVD) and chemical vapor deposition provide a means of providing hard coatings with a high fracture resistance. The growth, properties and functionality of PVD hard coatings depend strongly on the physical, mechanical and chemical properties of the substrate surface. Initially the substrate surface strongly influences the adatom nucleation mode, nucleation density and interface formation. Surface roughness causes the film to grow in a less than fully dense manner due to geometrical effects. The surface chemistry affects nucleation, diffusion and reaction at the substrate surface. In service, the substrate will often have to aid in supporting the applied loads, aid in corrosion protection and resist mechanical or thermal fatigue. Techniques for determining surface roughness and modifying the morphological, mechanical and chemical properties of substrate surfaces to aid in the functionality of hard coatings are discussed.

Multilayer, multicomponent, and multiphase physical vapor deposition coatings for enhanced performance

Hard physical vapor deposition (PVD) coatings are widely used today for enhanced performance, and PVD hard coatings have evolved because they can be deposited at temperatures much lower than those commonly needed for the chemical vapor deposition of coatings. Although binary coatings such as TiN are still very popular and are tried in many different applications, new multilayer, multicomponent, or multiphase coatings are finding successful applications. Multicomponent coatings such as TiAlNx or Ti(C,N) are better than TiN in certain tooling applications, and Ti0.5Al0.5N makes an excellent diffusion barrier in microelectronic devices. Reactively deposited coatings such as MoNx, CrNx, and NbNx all form multiple phases, and either individual phases or mixed phases of these materials are now being tested for tribological applications. Many nitride coatings such as β-Mo2N can extend the rolling contact fatigue life of rolling elements such as bearings by a factor of 5 or more. Multilayer polycrystalline TiN/NbN superlattice films have shown hardness as high as 5200 kgf mm−2, and other new superlattice films such as TiN/Ni are being developed. Although many of these new coatings will be tried on tools, the future for them lies beyond tooling. The ability to deposit these new coatings at low substrate temperatures without damaging the properties of the substrate, which can be done with plasma assisted PVD processes, will open up many new tribological and microelectronic applications.

IMPROVEMENT OF CUTTING TOOLS BY TiN PVD HARD COATING

ABSTRACT A review of recent results obtained in the field of cutting tools improved with a TiN physical vapor deposition (PVD) ion-plated hard coating is presented. Optimization of the tool material, tool surface morphology and interface problems between the TiN coating and the tool surface are discussed in view of their importance in optimum performance tests and the resulting workplace surface quality. The high effectiveness of the TiN PVD coating is demonstrated by selected data from our own data bank and from other sources on six groups of cutting tools, made of high-speed steels (HSS), powder metallurgical high-speed steels (PM-HSS) and of WC based hard metals. We also describe recently introduced, novel hard coatings (TiCN and TiAIN) for cutting tools, and new applications of cutting tools, improved by PVD hard coatings.