ICMCTF2018 Session G5: Hybrid Coatings and Hybrid System Processes

Arcing is an issue that extends throughout the field of plasmas that can cause expensive damage to industrial equipment. In magnetron plasmas, arcing is usually avoided by employing a preventative method, such as pulsed DC sputtering. This work superimposes a small AC signal onto the high voltage supplied to the DC cathode to observe the effects within a magnetron plasma. A Langmuir probe was inserted into an argon DC plasma formed by a two-inch magnetron gun. The voltage from the probe was read on an oscilloscope not only in the time domain to obtain the appropriate IV-curve, but also in the frequency domain to observe if the driven frequencies were able to propagate through the plasma. An 8 mm by 8 mm square probe was employed both parallel and perpendicular to the surface of the cathode. Variations depending on orientation were noted in the measured plasma temperature and density where typical density values of the observed plasmas were on the order of 10¹⁰ cm^-3. The applied AC signal was detected in the time domain measurements of the Langmuir probes only from probes oriented perpendicular to the surface of the cathode.

Surface engineering has been an area of interest for many decades. Initially, hybrid processes such as nitriding, anodizing and plating were applied to improve the surface properties of engineering materials such as steels and aluminum. Today, we are faced with many surface engineering challenges as the number of advanced materials increases and the “functionality” requirements of surfaces become more demanding. From metals to plastics to ceramics, the types of surface treatments and coatings are varied. For surface preparation, the energy and type of ion needed (etching/functionalization/cleaning) will vary with the application. Likewise, the properties of coatings and surface coating interfaces depend strongly on the type of impinging particles and their energies and reactivity. Several tools are available for “hybrid” processes where the energy and type of ions reaching a surface need to be controlled. Ion sources are typically used for pre-treatment of substrates, but sputtering magnetrons themselves can also be turned into sources of ions. Conversely, both can be used for depositing coatings. Advanced tools for surface engineering in today’s world involve an understanding of how sources can be driven (power supplies) and how combinations of technologies, both active (anode layer ion sources) and passive (anodes), allow us to change interfaces and coating properties. In this talk, we’ll explore such applications in the areas of glass coating, hard coatings and on polymers. We’ll discuss the combined used of secondary sources to boost and to decrease plasma density as well as the effects of adding positive pulses to traditional HIPIMS processes. With such positive pulses, the ion flux and energy can be controlled to the growing film after each negative pulse (deposition). The successful implementation of hybrid processes for coatings such as AlCrN, ITO, DLC and functionalized Ag will be presented.

As Hybrid technology , the Combinations of different PVD and PeCVD technologies like WC/C or Cr-DLC are state of the art technologies that are well established and industrialized but there are more possible idle technological combinations . Research was concentrated on two specific technology combinations:

1) Further investigations in DUPLEX DLC, an upstream NITRATION to increase surface hardness and increased resistance against plastic deformation with a subsequent tribological DLC coating reducing the coefficient of friction in one batch (INSITU). Goal of the study is discovering the properties ( adhesion , friction coeff , corrosion ) but also the potential to what extent existing sequent processes can be substituted and further, the feasibility of substituting used material / surface treatment combinations.

2) Co-deposition a simultaneous ARC and sputtering evaporation to combine the advantage of high adhesive hard coatings with embedded lubricant / tribiological nanoparticles. Today’s weakness in multi layered lubricant thin films are the limited working temperature of 300 °C and the fast elimination of the weak functional trobological layers by wear. Target of the test series is to figure out if lifetime can be increased significant by embedding lubricant particles into the hard coating by simultaneous evaporation of a different hard coatings (e.g. AlTiN) via ARC and materials with low friction coefficient (e.g. WC/C) via sputtering evaporation.

Borides of transition metals are very promising materials for a wide range of applications due to their high hardness, excellent wear, high temperature oxidation resistance and high thermal/electrical conductivity. Most widely used borides are iron and titanium borides. Iron borides are produced with diffusion based processes applied to iron and steel alloys. On the other hand titanium borides are produced either by boriding titanium or as coatings on different substrates using PVD or CVD methods. In this study we aimed to produce complex borides composed of Fe and Ti borides using hybrid process. For achieving this aim, low carbon steel substrates are alloyed with titanium using cathodic arc assisted process to produce iron-titanium alloy on the surface. This alloy is then borided using electrochemical boriding method. Produced mixed boride is characterized with respect to its structure, morphology and mechanical properties using XRD, SEM, FIB and ultra microhardness measurements. Tribological properties of the layers are determined using reciprocating wear tests against alumina balls. Results of the investigation revealed that it is possible to produce ultra hard surface layers (hardness above 40 GPa) by this hybrid method with excellent wear resistance.