APPLICATION OF HARD AND SELFLUBRICANT COATINGS TO GEAR HOBBING J.Rech , M.A.Djouadi and J.Picot Ecole Nationale Supérieure des Arts et Métiers, 71250 Cluny, France ABSTRACT : Coating technology is one means of achieving a crucial enhancement in tool performance especially in hobs which is the first tool to be coated in a wide scale. Nevertheless only few detailed analysis of wear mechanism have been done on field machines. The bifunctional coatings (combinaison of a tough hard and refractory coatings with a self lubricant coating with a good thermochemical and abrasion resistance but a lower hardness) are very interesting since it's difficult to get a simple coating having all these characteristics. The use of bilayer coatings raises several problems especially for dry cutting, therefore, in order to investigate the behaviour of these bifunctional coatings hobs have been coated by PVD methods. After the elaboration of a procedure for hobs testing, field tests have been performed. Results of tool life tests and investigations of tool wear mechanisms for different coated hobs will be presented and discussed. KEYWORDS : Coating, Dry cutting, Gear Hobbing.
1. Introduction Dry machining is one of the industry’s actual topics. Both economical and environmental factors contribute to the recent increase in dry machining. Manufacturers are looking for ways to reduce costs and, at the same time, avoid the environmental problems associated with the use of industrial lubricants. The investigations of tool manufacturers for developping the dry cutting consist of using hard and self lubricating coatings. The present study deals with the improvement of some coatings in the hobbing industry ((Ti,Al)N, TiN, MoS2). So as to reach these objectives, some studies have been engaged as follows : • 1st step : Behaviour evaluation of these coatings on two different susbtrates at low cutting speed (78 m/min) and with oil lubricant. These tests will bring informations on the performance of the coatings in comparison with the actual used TiN coating. • 2nd step : Investigation tests in milling at high cutting speed (135 and 180 m/min) in dry conditions, so as to evaluate the performance of these coatings at high temperature.
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• 3rd step : Through the conclusions of the second step, propositions for the design of a new generation of coated hobs adapted for high speed and dry cutting with HSS substrate. Investigations the coatings behaviour in dry hobbing conditions and high cutting speed.
2. Coatings deposition and characterization Two kinds of hobs were used in this study, segmented and integral hobs. The hobs were manufactured by the companies (Saazor, Vergnano) and coated by the companies (Bloesch, Genta, Platit, Saazor), details about coatings are given Fig. 1. The surface morphology, composition and thickness of the films were studied by scanning electon microscope JEOL 5900LV equipped with energy dispersive X ray analyser (EDX). The thickness values were confirmed by Calotest measurements and presented Fig. 1. Coating TiN (=> TiN-1)
Coating Manufacturer Saazor
TiN ( => TiN-2)
Genta
TiN-1+MoS2 (Ti,Al)N
Saazor + Bloesch Bloesch
(Ti,Al)N+MoS2
Bloesch
System of deposition Balzers BAI 830 Platit system [FRA95] Balzers BAI+ Platit system Platit system [FRA95] Platit system [FRA95]
Coating thickness 3.6µm 6.5µm 5µm 2.9µm 2.5µm
Figure 1. Coating deposition conditions
3. Wear tests procedures This paragraph presents the wear tests procedures which have been performed on segmented hobs and integral hobs (Fig. 2 and 3) in three different cutting applications. • The first application consist in hobbing a gear (steel 27MnCr5 – 185HB) in wet condition (Oil) at low cutting speed (Vc = 78m/min – feed = 3.2mm/rev shifting = 0.6mm - Hobbing cycle described in Fig. 2). These tests have been performed in a gear box factory (Peugeot-Citroën). • The second application consist in milling a workpiece (same steel and hardness as the hobbed gear) with two different cutting speeds in dry cutting conditions (Vc = 135-180m/min, feed = 0.8mm/rev - down milling, Fig. 3). These tests have been performed in the machining department of the ENSAM.
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• The third application consist in hobbing a gear (steel 27MnCr5 – 185HB) in dry condition at high cutting speed (Vc = 160m/min – feed = 3mm/rev - Shifting = 10mm - Hobbing cycle described in Fig. 2). These tests have been performed in the same gear box factory (Peugeot-Citroën). Obviously the milling test will not completely represent the behaviour of the tool during hobbing, but it was the single test practically possible in our case. However this test enable to compare the behaviour of different zone of the coated hob (one zone for hobbing and two zone for milling) using the same coating, geometry and substrate.
Figure 2. Hobbing process during field tests
Figure 3. Milling process during laboratory tests
3.1. Tool preparation • Five segmented hobs were manufactured by one tool producer with a constant process and with a constant quality of substrate M35. • Two integral hobs were manufactured by a second tool producer with a constant process (different from the following one) and with a constant quality of substrate ASP30. • Three integral hobs were manufactured by the second tool producer with a constant process (different from the following ones) and with a constant quality of substrate ASP2052. No hob has been reground and recoated for these tests. These conditions were thought to be the best way to quantify the behaviour of the coatings, without any influence of the susbtrate or the surface preparation as described by [KAU87, TON98].
3.2. Tool design • Segmented Hobs : 17 flutes, Steel Z85 WDKCV 06-05-05-04-02 or HS 6-5-3-9 (M35, Norm EN10027-1), modulus = 2.1171, external diameter = 107, total length = 210mm.
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• Integral Hobs : 22 flutes, Steel Z130 KWDCV 09-06-05-04-03 or HS 6-5-2-5 (ASP30, Norm EN10027-1), modulus = 2.1171, external diameter = 107, total length = 210mm. • Integral Hobs : 22 flutes, Steel Z160 WKVCD 11-08-05-05-02 (ASP2052, Norm EN10027-1), modulus = 2.5541, external diameter = 107, total length = 210mm. The other details of the tools are confidential.
4. Hobbing tests results in wet conditions and at low cutting speed This paragraph presents the wear experiments carried out in the gear box factory. Wear has been observed after each shifting (100 workpieces). The critical wear observed after hobbing is flank wear. The Fig. 6 and 7 presents the maximal flank wear measured in hobbing tests versus the number of shiftings. Industry uses HSS tools to a maximum flank wear of Vb = 0.3mm because of gear accuracy. The evaluated coatings are the well known TiN deposited by two different methods and with two different thicknesses. The TiN-1 (3.6µm) is the coating used currently in the gear box factory. It will be the reference during these tests. The TiN-2 (6.5µm), TiN+MoS2 (5µm), (Ti,Al)N (2.9µm), (Ti,Al)N+MoS2 (2.5µm) are new coatings for the hobbing process. The five different coatings have been evaluated with five segmented hobs (substrate M35). Only two different coatings (TiN-2 (6.5µm), (Ti,Al,)N (2.9µm)) have been evaluated with two integral hobs (substrate ASP30) so as to investigate the effect of the substrate on the coatings behaviour. In both cases, the cutting conditions are exactly the same.
4.1. Typical wear observed after the hobbing tests at low cutting speed and in wet conditions The critical wear observed after hobbing is flank wear (Fig. 3). The crater wear has always been contained which proves the protection effect of the hard coatings against abrasion, adhesion and diffusion wear. In the case of gear hobbing with non coated tools, the critical wear is always crater wear. A single hobbing test with a non coated segmented hob has been performed in the gear box factory so as to confirm it. A scanning electron micrography of a tooth shows the presence of a deep crater on the rake face, Fig. 4.
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Figure 4. Crater wear on a non coated hob after a hobbing test (Vc = 78m/min – Oil lubricant – M35 Substrate) In fact, the most important solicitation is the shear stress on the top of the teeth, caused by the abrasion on the flank. On Fig. 5, it is possible to observe the asymmetrical wear of the teeth, caused by the asymmetrical hobbing process, as it is well known in hobbing process. After hobbing, no coating is present around the cutting edge (only substrate), especially on the rake face because of the chip abrasion and at the beginning of the flank face because of the workpiece steel abrasion.
Figure 5. SEM and optical pictures of a typical wear observed after hobbing (Vc = 78m/min – Oil lubricant – TiN coating – M35 substrate)
Flank wear Vbmax [mm]
0,35 0,3 0,25 0,2 TiN-1 (3,5µm) TiN-2 (6,5µm) TiN-1+MoS2 (5µm) TiAlN (2,9µm) TiAlN+MoS2 (2,5µm)
0,15 0,1 0,05 0 0
2
4
6
8
10
Number of shiftings
Figure 6. Evolution of flank wear during hobbing tests (Vc = 78m/min – Oil lubricant – M35 substrate)
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Flank wear Vb max [mm]
0,25 0,2 0,15 TiN-2 (6,5µm) TiAlN (2,9µm)
0,1 0,05 0 0
5
10
15
20
25
Number of shiftings
Figure 7. Evolution of flank wear during hobbing tests (Vc = 78m/min – Oil lubricant – ASP30 substrate)
4.2. Comparison of the TiN and the (Ti,Al)N coatings The main result in hobbing at a cutting speed of 78m/min and with oil, is that the best coating are the two TiN coatings, which have a similar behaviour. The worst one is the (Ti,Al)N coating which does not resist and disappear quickly from the cutting edge. This difference is observed irrespective of the substrate and the deposition process and thickness (TiN). About these results, some comments on the tests conditions can be done : • The cutting speed in hobbing is relatively low in comparison with the cutting speed usually used in milling processes. • The operation is done with oil lubricant, which have a cooling effect and decrease the temperature between the tool and the chip. This allows to conclude that the cutting temperatures should be low, but no precise value can actually be given. • The presence of oil may inhibit the properties of the (Ti,Al)N coating (high oxidation resistance, low friction coefficient). According to [KAL98, RAB99], the measured hardness of the TiN at room temperature : Hv0.01 ~ 2200-2400 and the (Ti,Al)N : Hv0.01 ~ 2400-2800, which are not extremely different. As observed of the Fig 6 and 7, the TiN has the best behaviour irrespective of the lower hardness and the (Ti,Al)N is not dedicated to the hobbing in these conditions. Indeed The TiN coating represent today 90% of the coated hob in industry. These conclusions are in accordance with other studys [KON92, WER98, CRA98, TON98] which have shown that the (Ti,Al)N coating is not adapted to interrupted cutting processes at low temperatures (so as in our case), but is more dedicated in straight cutting processes at high temperatures (drilling, turning, tapping).
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4.3. Behaviour of the MoS2 coating This soft coating is expected to replace the cutting fluids, because of it’s low friction coefficient with steel (µ = 0.04-0.09 with steel according to [WEU99]). In these hobbing tests with entire oil, the MoS2 should theoriticaly not bring anything to the « lubrication » effect and to the wear resistance, because oil improve this low friction coefficient. The results observed in Fig 6 show that the MoS2 improve the wear behaviour of the (Ti,Al)N but decrease the wear behaviour of the TiN. The explanation of the MoS2 effect is not completely clear at the moment. Visual assessment of the MoS2 coating show that the layer is no longer present after a few seconds (Fig. 8). An energy dispersive X ray analysis on the teeth have shown that the MoS2 was completely removed from the contact zone between chip-tool and workpiece-tool. The EDX analyse has determined the presence of the MoS2 in none cutting zone, which prove that the MoS2 is not solved with entire oil. According to [WEU99], the MoS2 diffuse in the surface structure of the inner layer (TiN and (Ti,Al)N). This may explain that the additional layer could disturb the hard coating in low temperature conditions, but in our case, this diffusion has not been observed. According to [WEU99], the MoS2 can bring a benefit effect when the temperature is high (MoS2 becomes fluid). In these tests, the low cutting speed and the use of oil limit the temperatures at the interface of the tool. So the effects of the MoS2 can not improve the life duration in these cutting conditions.
Figure 8. Lack of MoS2 on the rake face in the contact zone of the chip (Vc = 78m/min – Oil lubricant – TiN+MoS2 coating – M35 substrate)
4.4. Behaviour of the substrate The comparison of the TiN-2 wear curves in Fig 6 and 7 shows that the substrate has an influence on the life duration of the hobbing process. In our case, the ASP30 allows about 3 times more shiftings (3 times more machined workpieces) before resharpening
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Number of shiftings Vb=0.2mm
and recoating. The sindered high speed steel has the highest hardness, which is the main parameter that influence the resistance of the susbtrate in these cutting conditions. 18 16 14 12 10 8 6 4 2 0 M35
ASP30 Substrate
Figure 9. TiN Coating performance with two different substrates (Vc = 78m/min – Oil lubricant)
5. Milling tests results in dry cutting conditions Let us now presents the wear experiments carried out in milling so as to investigate the performance of the hard coatings at high cutting speed and in dry cutting conditions. During the test, wear has been measured after each 500mm. Our objective with the milling tests was to classify the coatings and not to quantify the life duration, because a hob is not a mill and the results can only be considered as qualitative results. That is why some experiments have been stopped before reaching a flank wear of Vb = 0.2mm, especially when the differences between the coatings behaviour were very important since the beginning of the tests. The Fig. 13 and 14 presents the maximal flank wear measured in milling tests with segmented hobs (substrate M35) through the cutting length for two cutting speed (135 and 180 m/min). Before analysing the results, some comments about the tests conditions have to be given. • These tests have been performed in dry conditions and at high cutting speed (intended for a HSS hob not for carbide hob). These conditions involve high cutting temperature, between 600-1100°C depending of the position on the tool, as decribed by [LEC95]. The high temperatures and the avoidance of the lubricant increase the oxidation wear, especially in interrupted cutting processes like milling, because of the alternative contact between the teeth and the workpiece. The oxidation will be an important parameter, which is favorable to the (Ti,Al)N coating, as described by [WER98], because of the creation of a Al2O3 film on the external layer when the tooth is no more in contact with the workpiece.
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• The high temperatures will decrease the hardness of the coatings. So the red hardness will be an important parameter. The (Ti,Al)N is well known [KAL98] to have a higher hardness at high temperature (Hv0.01 ~ 1500 at 1000°C) in comparison with the TiN (Hv0.01 ~ 500 at 1000°C) [QUI88]. So the (Ti,Al)N should have a better wear resistance at high cutting speed.
5.1. Typical wear observed after the milling tests Three kind of wear have been observed in these milling experiments : flank wear (Fig 10), crater wear (Fig 11), plastic deformation (Fig 12). The flank wear is the usual wear observed in milling. This wear is obtained when using low cutting speed and the hardest substrate ASP30. The crater wear appear when increasing the cutting speed and the plastic deformation is only present with the smoothest substrate M35 at high cutting speed. These three different kind of wear correspond to three level of thermomechanical loads on the teeth. The crater wear becomes dangerous when the temperature on the rake face is high. This decrease the properties of the coatings and allows a chemical diffusive wear, combined with an oxidation and abrasion wear due to the alternative hobbing process. The three kind of wear are symmetrical and concentrated on the top of teeth because of the symmetrical milling process. The only wear measured is the flank wear because of the experimental problems for measuring the other kind of wear.
Figure 10. Flank wear observed after milling (Vc = 135m/min – Dry cutting – TiN coating – ASP30 substrate)
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Figure 11. Crater wear observed after milling (Vc = 180m/min – Dry cutting – (Ti,Al)N coating – ASP30 substrate)
Figure 12.. Plastic deformed tooth observed after milling (Vc = 180m/min – Dry cutting – (Ti,Al)N coating – M35 substrate)
0,3 Flank wear Vb max [mm]
Flank wear Vb max [mm]
0,3 0,25
Flank wear
0,2
TiN-2 (6,5µm) TiAlN (2,9µm)
0,15 0,1 0,05 0
0,25
Plastic deformed teeth 0,2 0,15
TiN-2 (6,5µm) TiAlN (2,9µm)
0,1 0,05 0
0
5
10 Cutting Length [m]
15
20
0
Figure 13. Evolution of flank wear during milling tests (Vc = 135m/min – Dry cut – M35 sub)
5
10 Cutting Length [m]
15
20
Figure 14. Evolution of flank wear during milling tests (Vc = 180m/min – Dry cut – M35 sub)
10
0,3
0,2
TiN-2 (6,5µm) TiAlN (2,9µm)
0,15
Flank wear
0,1 0,05
Flank wear Vbmax [mm]
Flank wear Vbmax [mm]
0,3 0,25
TiN-2 (6,5µm) TiAlN (2,9µm)
0,25 0,2 0,15
Crater wear
0,1 0,05 0
0 0
5
10
15 20 25 Cutting Length [m]
30
0
35
5
10
15
20
25
Cutting Length [m]
Figure 15. Evolution of flank wear during milling tests (Vc = 135m/min – Dry cut – ASP30 sub)
Figure 16. Evolution of flank wear during milling tests (Vc = 180m/min – Dry cut – ASP30 sub)
5.2. Experimental results The first analysis of the figure 13 is that the TiN has a better wear resistance in milling at a cutting speed of 135m/min. The bad behaviour of the (Ti,Al)N in these conditions may be explained by the thermomechanical properties of this coating for these loads (low cutting temperatures and interrupted cutting) as for the hobbing tests. The second analysis is that the (Ti,Al)N has a disastrous wear at a cutting speed of 180m/min with the M35 substrate. One explanation may be that the susbtrate M35 has completely lost his mechanical properties with the high temperatures. An analyse of the wear shows that the edge of the teeth were strongly plastic deformed (Fig 12) which confirmed this explanation. As a consequence, the milling tests results at high cutting speed can not bring any information about the coating behaviour because of the worse susbtrate properties at these temperatures. It has been decided to investigate the same tests with another substrate, more dedicated to the high speed and dry cutting. The figures 14 and 15 present the maximal flank wear measured in milling tests with integral hobs (substrate ASP30) through the cutting length for two cutting speed (135 and 180 m/min). At low cutting speed, the TiN has also a better wear resistance compared to the (Ti,Al)N, which prove the reliability of the previous results. At high cutting speed, the cutting edge of the teeth ((Ti,Al)N – ASP30) are not plastic deformed, but a crater wear appear on the rake face (Fig. 11). This proves the high thermomechanical load on the teeth of the hob. It can be noticed that this kind of wear may occur in hobbing due to the hard conditions of cutting. However it can be observed that, at high cutting speed, the (Ti,Al)N on ASP30 has the best flank wear resistance and the TiN is no more efficient. This proves that the red hardness and the high oxidation resistance of the (Ti,Al)N may participate to this good behaviour.
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Flank wear Vbmax [mm]
What is more surprising is that the (Ti,Al)N coating has a better flank wear resistance at 180m/min than at 135m/min (Fig. 17). This unusual behaviour may be explained by a more suitable thermomechanical loads of (Ti,Al)N at 180m/min then at 135m/min. This phenomenon has also been observed by [KOB99] in a hobbing test with coated carbide tools. 0,2 0,18
TiAlN (2,9µm) Vc=135m/min
0,16 0,14
TiAlN (2,9µm) Vc = 180m/min
0,12 0,1 0,08 0,06 0,04 0,02 0 0
5
10 Cutting Length [m]
15
20
Figure 17. Comparison of the wear behaviour of the (Ti,Al)N for two cutting speed (Vc = 135 and 180m/min – Dry cutting - ASP substrate)
6. Hobbing tests in dry and high speed conditions 6.1. Conclusions and propositions for the design of coated hobs adapted for the dry and high speed cutting Through the presented experiments, one may conclude : • The substrate M35 is not adapted for the cutting at high temperature (High speed and dry cutting) • The substrate ASP30 is more adapted for the cutting at high temperature. • The TiN coating is the best coating for hobbing processes at low cutting speed with oil. The (Ti,Al)N has a disastrous behaviour in these conditions. • The (Ti,Al)N is the best coating for dry milling at high speed and dry cutting. • The MoS2 doesn’t bring a benefit effect at low temperature (low cutting speed and oil) and even have a negative effect by disturbing the inner layer. Nevertheless, a significant improvement may be observed at high temperature. The objective of the study is to bring reliable information so as to design new HSS hob for the dry and high speed cutting. From the experimental results presented, the following ideas may be proposed : • Hobs must be manufactured with a substrate adapted for the high temperatures and the high thermomechanical loads. In accordance with the tool manufacturer, ASP2052 sintered HSS was used.
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• Hobs must be coated with a coating adapted to the thermomechanical loads of the teeth. The (Ti,Al)N coating seems to be efficient at high speed and dry cutting conditions. In addition, the MoS2 should decrease the friction coefficient on the rake face and limit the crater wear.
6.2. Hobbing tests results at dry and high speed cutting Tests have been performed in the gear box factory on a new machine dedicated to dry hobbing. The cutting conditions are as follow : Vc = 160m/min – feed = 3mm/rev Shifting = 10mm. The speed is relatively high so as to evaluate the different behaviour of the three coating (TiN, (Ti,Al)N, (Ti,Al)N+MoS2). The shifting is also high so as to decrease the concentration of energy between two hobbing cycle. The first analyse is that the hob are very hot after a complete shifting (100°C), which proves the severe conditions compared to the first hobbing tests with oil.
6.3. Typical wear observed after the dry hobbing tests For all the coatings, the main wear observed is the crater wear, Fig 20. These results are similar to those observed in the milling tests at 180m/min and may be explained by the severe conditions during cutting. Nevertheless, the substrate has never been plastic deformed which confirms the reliability of the substrate choice. The flank wear has never been higher than 0.1mm (Fig 18) which is very low compared to the first hobbing tests. The gear manufacturer prefers to have a crater wear than a flank wear because of the better size accuracy. The tests have been stopped before the breakage of the teeth edges. The crater always starts in the right top corner of the teeth (Fig 18) and then appears in the left top corner (Fig 19). Then the two craters increase and rejoin each other (Fig 20). At this time, the limit of use is not far. Tests were performed in industrial environment, so the crater evaluation was only qualitative. The test was stopped before the edge breaking.
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Figure 18. Apparison of crater wear in the top right corner after 400 machined workpieces in dry hobbing (Vc = 160m/min – Dry cutting – TiN coating – ASP2052 substrate)
Figure 19. Apparison of crater wear in the left right corner in dry hobbing (Vc = 160m/min – Dry cutting – TiN coating – ASP2052 substrate)
Figure 20. Junction of the crater wear in dry hobbing (Vc = 160m/min – Dry cutting – TiN coating – ASP2052 substrate)
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6.4. Experimental results
Number of machined workpieces
As shown in the Fig 21, the coating (Ti,Al)N+MoS2 exhibit the best behaviour in these conditions and the worst one is the TiN. This confirms our tests in milling at high cutting speed with the ASP30 substrate. The crater wear observed is mainly caused by the diffusion and the abrasion on the rake face. One explanation of the (Ti,Al)N good behaviour is its higher hardness [KAL98 : Hv0.01 ~ 1500 at 1000°C in comparison with the TiN : Hv0.01 ~ 500] and its better oxidation resistance at high temperature and its chemical stability. An other explanation may be the presence of an alumina film on the rake face during the no-cutting time. This alumina film may protect the teeth against the oxidation [WER98]. The (Ti,Al)N is well known [KAL98] to have a higher hardness at high temperature (Hv0.01 ~ 1500 at 1000°C) in comparison with the TiN (Hv0.01 ~ 500 at 1000°C) The second analyse is that the MoS2 enhance the wear behaviour of the (Ti,Al)N at this high level of temperature. According to [WEU99, RAB99], the MoS2 becomes smoother and decrease the friction coefficient between the chip and the rake face. The low friction coefficient reduce the temperature on the rake face and also limit the effect of steel abrasion. But even if the (Ti,Al)N+MoS2 coating brings a significant increase in the number of machined workpieces (two times more than the TiN), the crater wear is always present, but appears later and increases more slowly. 1200 1000
End of life Crater wear start
800 600 400 200 0 TiN-2 (6,5µm)
TiAlN (2,9µm)
TIAlN+MoS2 (2,5µm)
Figure 21. Comparison of the wear behaviour in dry hobbing conditions (Vc = 160m/min - Hobs substrate ASP2052)
7. Conclusions The objective of the study was to bring reliable information so as to design new HSS hob for the dry and high speed cutting. The experimental investigations have shown that the dry and high speed hobbing needs a substrate with a high hardness and a high
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oxidation resistance at high temperature. The sintered high speed steel, as the ASP2052, seems to be adapted to this kind of applications. The second result of our investigations is that the TiN has the better wear behaviour at low cutting speed and with oil lubricant. The (Ti,Al)N is more dedicated to the use in dry and high speed hobbing (40% more workpieces machined than with the TiN) but can not solve the apparition of the crater wear which is the main kind of wear at this high level of thermomechanical loads. The third result is that the MoS2 can improve the life duration of the hob in dry and high speed hobbing (40% more workpieces machined than without MoS2) by its low friction coefficient at high temperature which limits the apparition of the crater wear.
8. Acknowledgements The work described in this paper was undertaken with support of the EEC in a special research programme (CRAFT N°BES2-5317) on coating technologies. The authors extend their sincere appreciation and gratitude to Peugeot-Citroën, Saazor Wälztechnik, Vergnano, Genta, Platit-Bloesch, for their support to this study and as well as Prof. E. Bergman (EIG - Switzerland) for his cooperation.
9. References [FRA95] D.Franchi, F.Rabezzana, H.Curtins, Proc. Fourth Euro-Ceramics Conference, Riccione, 1995. [KAU87] M.Kauven : Wälzfräsen mit Titannitrid-beschiteten HSS-Werkzeugen, June 1987, Dissertation TH Aachen. [TON98] H.Tonshoff, B.Karpuschewski, A.Mohlfeld : Influence of drill tool design on cutting performance in dry machining, Proc. International Seminar : Improving Machine Tool Performance, San Sebastian (Spain), July 1998, pp677-687. [RAB99] F.Rabezzana, S.Durante and M.Comoglio : High perfomance gears hobbing, 1999, Advanced Manufacturing Systems and Technology N°406 pp207-214. [KAL98] E.Kalhofer : Dry machining – Technology and requirements to the machine tool, International Seminar : Proc. Improving Machine Tool Performance, San Sebastian (Spain), July 1998, pp633-641. [KON92] W.Konig, R.Fritsch, D.Kammermeier : New approaches to characterizing the performance of coated cutting tools, Annals of CIRP, vol 41/1/1992, pp49-54.
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[WER98] R.Wertheim, T.Vinas : Developpment and application of new cutting tool materials, Proc. International Seminar : Improving Machine Tool Performance, San Sebastian (Spain), July 1998, pp303-313. [CRA98] N.Crauwels, K.De Bruyn, N.Van Stappen, J.P.Celis, L.Stals, : Ecological cutting : Dry, minimal quantity lubrication or ecological cutting fluids, Proc. International Seminar : Improving Machine Tool Performance, San Sebastian (Spain), July 1998, pp703-714. [LEC95] C.Lecalvez : Etudes des aspects thermiques et énergétiques de la coupe orthogonale d’un acier au carbone, PhD Thesis ENSAM Paris, 21/12/1995. [KOB99] C.Kobialka : Possibilities for reducing production costs in cylindrical gear hobbing and shaping, Paris 1999, Proc. International Conference on Gears, pp1609-1619. [WEU99] H.Weule, J.Schmidt, O.Doerfel, A.Huhsam, Dry machining for gear shaping, Paris 1999, International Conference on Gears. [QUI88] D.T.Quinto, J. Vac. Sci. Technol. A6 (3), May/Jun 1998, pp2149-2157.
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