ICMCTF2007 Session G6: Surface Pre-Treatment, Coating Post-Treatment and Duplex Technology

Wednesday, April 25, 2007 8:00 AM in Room Royal Palm 4-6

Wednesday Morning

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8:00 AM G6-1 Manipulation of Coating and Subsurface Properties in Reconditioning of Carbide Cutting Tools
F. Klocke, T. Schroeder, E. Bouzakis, A. Klein (RWTH Aachen University, Germany)

The physical properties in the surface layer of carbide tools have a significant influence on the tool wear behaviour. In gear hobbing with carbide tools, the phenomenon that the tool life decreases with increasing number of reconditioning cycles has been identified. It is shown that there is a significant correlation between the amount of residual stress in the subsurface and the tool life, and that there is a steady decrease of residual compressive stress from cycle to cycle. This decrease can be linked to the thermal load in the PVD process.

Through micro blasting, the initial stress can be readjusted, and good tool lives or tool lives that are superior to the life of unblasted new tools could be obtained in laboratory studies and trials in an industrial environment. Besides these successes, disappointments have also been encountered. Since many parameters can and must be adjusted in the micro blasting process, blasting is likely to have no or even a negative effect if the set of parameters is not set right. In order to get a better understanding of the aerosol micro blasting technology, fundamental studies on the influence of blasting parameters on the energy content of the aerosol have been conducted. In these studies, several phenomena have been identified. Finally, blasting of coated tools has also been applied successfully with regard to tool life increase. In ongoing research, the effects of blasting of coated tools with regard to residual stress in the coating and the coating´s cycle fatigue are studied. These findings will also be presented.

8:40 AM G6-3 Mechanical Pre- and Post-Treatment of PVD-coated Cutting Tools
T. Michalke, F. Mumme, F. Jungblut (Oerlikon Balzers Coating Germany GmbH, Germany)
The usage of pre- and post-treatment of tools for PVD coating is a key knowledge to optimize the coating and performance results. Pre-treatment is not only important for deburring, but also to increase the material density in the surface region in the first atomic layers. In addition pre-treatment methods can be used to prepare special rounded cutting edges. Post-treatment is mostly important for the smoothness of the flute and decreasing of friction. But it can also reduce the residual stress in the coating. We will show different methods of mechanical tools treatment, compare their results and give an overview over their advantages and disadvantages.
9:00 AM G6-4 Accelerated Drill Testing Lifetime Response of Coated and Uncoated HSS Jobber Drills to Deep Cryogenic Treatment, Applied at Various Stages of Manufacture
S.J. Dowey (Surface Technology Coatings, Australia); E. Thompson, T. Vom Braucke, E.D. Doyle (Swinburne University of Technology, Australia)

A commercially available process which thermally cycles products to cryogenic temperatures has been assessed with regard to performance benefits claimed for products treated by the process. This was measured by accelerated drill testing in P20 steel to determine any change in lifetime. Drills were HSS and the treatment applied at selected points during the heat treatment of the drill blanks prior to grinding and also as finished. When tested all applications failed to show any significant improvement in drill life when compared to an untreated group of drills from the same batch of drill blanks. The trials were repeated and analysed using design of experiment techniques, on a larger sample of finished jobber drills, manufactured for internal testing purposes, which included the effect of a surface coating.

TiN was applied to a selected mix of treated and untreated drills and the design analysed for the effect of both coating and cryogenic treatment. A further group of TiN coated untreated drills was cryogenically treated and tested. Although the results from this trial show large differences between the samples, unless early life failures are censored, these are not statistically significant given the variance in the raw data. Microstructure and fracture cross sections are also presented as well as a critique of the statistical techniques employed to reach this conclusion.

9:20 AM G6-5 Study on the Effects of MF- and Plasmabooster Etching on the Adhesion of High Performance Coatings
R. Cremer, M. Alunovic, H.G. Fuß (CemeCon AG, Germany); A. Atiser, J.M. Schneider (RWTH Aachen University, Germany)
In previous work it was demonstrated the strong correlation of microblasting as a pre-treatment technique to the final surface topography respectively the coating adhesion. Extremely good values for coating adhesion can be reached through a super-imposed mid-frequency ion etching device in combination with the high ionization sputtering (h.i.s.®) process, too. By the introduction of the Plasmabooster technology into the h.i.s.® process new standards are set in generation and controlling of the etching as well as the coating plasma. In this work the influence of MF- and Plasmabooster etching in an Argon and Argon/Hydrogen atmosphere on coating adhesion for cemented carbide respectively ceramic tools are studied by means of SEM, AFM (atomic force microscopy) and scratch-tester.
9:40 AM G6-6 Influence of Edge Preparation on the Performance of Coated Cutting Tools
T. Cselle, M. Morstein, C. Buechel, O. Coddet (Platit AG, Switzerland); M. Ruzicka, M. Sima (Pivot a. s., Czech Republic); S. Reich, P. Preiss (GFE, Germany)
Edge preparation before coating influences the performance of cutting tools enormously. The paper gives an overview and evaluation of the most used processes for edge preparation; brushing, drag grinding, micro blasting, magnet finishing and laser masking. A general applicable pre- and post-treatment method does not exist. The treatment must be adapted to the tools; inserts, drills, taps, end mills and hobs, and especially to their applications, depending on the work piece materials, cutting and machine conditions. To develop and to choose the optimum method and process you have to find the correlation between the edge treatment and the performance of the coated tools. The paper gives guidelines and shows industrial applications with PVD coated tools, especially with nanocomposite coatings.
10:20 AM G6-8 Pre-Coating Cutting Edge Preparation of Machining Tools by Abrasive Water Jet Blasting
K. Weinert (University of Dortmund, Germany); D. Koetter (Rothe Erde GmbH Lippstadt, Germany); I. Terwey (University of Dortmund, Germany)
Cutting edge preparation increases the capability of machining tools. Reducing the cutting edge roughness and creating a defined rounding of the cutting edge are the objectives of edge preparation. A rounded cutting edge features a higher cutting edge stability and positively affects the residual stress condition within the coating in the cutting edge region. This leads to an improved tool life behaviour. Abrasive water jet blasting, brushing and slip grinding are industrial techniques for cutting edge treatment. But only abrasive water jet blasting allows to furnish the different edges of a cutting tool with different edge radii. Furthermore abrasive water jet blasting induces residual compressive stress into the treated tool. When applying a PVD-coating process residual compressive stress within the tool improves the adhesion between coating and substrate. The research activities described in this paper aim at the cutting edge preparation of HW-machining tools by the application of an abrasive water jet blasting process. Basic investigations analyze the material removal mechanism when blasting cemented carbide with abrasive particles. The variation of the process parameters leads to the determination of values, which generate edge radii common in industrial practice. Based on these results the cutting edge preparation of a twisted drill is developed. The applied process design creates evenly rounded major cutting and chisel edges with little impact on the minor cutting edges. The advantages of a pre-coating cutting edge preparation are proven through the results of drilling tests. During these tests PVD-TiAlN-coated tools are used.
10:40 AM G6-9 Surface Treatment of Cutting Tools: The Importance of Pre- and Post-Treatment.
G. Hakansson (Ionbond Sweden AB, Sweden); C. Schunk (Ionbond Coburg, Germany)
The use of PVD coatings on cutting tools for improved function is well established since more than two decades. It is also an area where the development of new, high performance coatings still is an important factor for market success. During the last years it has become more and more obvious that the practical function of the coated tool is not primarily limited by the coating properties like hardness, ductility, thickness etc. The modern coatings are in fact, in many cases, not used to their full potential due to problems related to the surface texture. The result being premature failure due to e.g. work material stuck on the tool surface and/or problems of chip removal in dry machining. The increased focus on different types of pre- and post treatment methods is therefore a natural step in order to prepare the tool to use the coating properties to its full potential. The importance of a well controlled surface structure, with a high reproducibility, has in many cases proven to be as important as the choice of the coating itself. In addition, the use of post-treatment has also proved to have significant impact on the end result in different applications. Results from different types of automatized dry- and wet-blasting techniques used both as pre- and post-treatment will be presented. Their effect on surface structure and actual function on different types of cutting tools as drills and gear cutting hobs will be discussed.
11:20 AM G6-12 Hardness Consideration of NiTi and NiTiAl Thin Films for Various Annealing Temperatures
K.-T. Liu, J.G. Duh (National Tsing-Hua University, Taiwan)
Ni50.54Ti49.46 and Ni45.61Ti49.26Al5.13 thin films were fabricated by DC magnetron sputtering and post-annealed at 500; 525; 550; 600 and 650°C. The crystallization kinetics of as-deposited NiTiAl films was investigated by differential scanning calorimetry (DSC). Hardness and grain size of NiTiAl films annealed at different temperature were evaluated by nanoindentation test and X-ray diffactometer (XRD), respectively. The peak hardness of Ni45.61Ti49.26Al5.13 film was 12.9 GPa at 550°C which was significantly improved as compared to Ni50.54Ti49.46 film with 8.8 GPa. Hardness of both as-deposited and heat treated Ni45.61Ti49.26Al5.13 film increased with co-deposition of aluminum due to the effect of solid solution in the NiTi system. The appropriate annealing temperature for specific Ni45.61Ti49.26Al5.13 film could be chosen at 550°C on the basis of the hardness consideration.
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