Modification of surface finish produced by hard turning using superfinishing and burnishing operations

Journal of Materials Processing Technology 212 (2012) 315–322

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Modification of surface finish produced by hard turning using superfinishing and burnishing operations ˙ Wit Grzesik ∗ , Krzysztof Zak Department of Manufacturing Engineering and Production Automation, Opole University of Technology, P.O. Box 321, 45-271 Opole, Poland

a r t i c l e

i n f o

Article history: Received 23 July 2011 Received in revised form 21 September 2011 Accepted 21 September 2011 Available online 29 September 2011 Keywords: Hard turning Superfinishing Burnishing 2D and 3D surface roughness

a b s t r a c t In this study the surface finish produced by hard turning of a 41Cr4 low-alloy steel quenched to about 60 HRC hardness, using mixed Al2 O3 –TiC ceramic inserts, was subsequently modified by superfinishing and multipass burnishing operations. In the case of hard turning surfaces were produced by conventional and Wiper cutting tool inserts. The main goal of this study was to examine how additional abrasive and non-removal technological operations change 2D and 3D roughness parameters and enhance service properties of the machined surfaces. It was documented that both superfinishing and burnishing operations allow to obtain smoother surfaces with lower surface roughness and better bearing characteristics.

1. Introduction Machining of hardened materials (steels and cast irons) became an effective and economically efficient removal method of producing parts in many technologically top-level manufacturing branches (Grzesik, 2008) such as automotive (Klocke et al., 2005), bearing, hydraulic and die and mold making sectors (Davim, 2009). Its wide popularity and attractiveness result mainly from possibilities of obtaining high surface finish when using advanced cutting tools materials (mixed ceramic or CBN tools), reducing machining time and cost, and improving overall product quality, or partly eliminating grinding operations. However, hard machining did not replace grinding operations in such an extent as expected a few decades ago despite above-mentioned technological capabilities. As a result, recently, an integration of these leading machining processes, performed by CBN cutting tools and abrasive wheels, in one multitasking turn-grinding machining center was done. However, simultaneously performed grinding and hard turning operations demand not only the machine components with sufficient stiffness but also a good damping to minimize the vibrations during the process (Klocke et al., 2005). In some cases, it has been allowed to replace hard turning and grinding operations with laser-assisted machining (LAM) for machining hardened steel shafts and substantially larger material removal rates with a good surface finish of Ra less than 0.3 ␮m was achieved (Ding and Shin,

∗ Corresponding author. Tel.: +48 77 4006 290; fax: +48 77 4006 342. E-mail address: [email protected] (W. Grzesik). 0924-0136/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2011.09.017

© 2011 Elsevier B.V. All rights reserved.

2010). The second trend observed is to finish hard turned surfaces with special abrasive operations, such as finishing grinding (Garcia Navas et al., 2008), superfinishing, belt grinding (Grzesik et al., 2007) and honing (Hashimoto et al., 2006) or mass finishing (Hashimoto et al., 2007). Relatively new trend emerging recently in industry is to burnish the hard turned or milled surfaces, like softer steel surfaces, using commercial burnishing tools. This innovative surface improving technique was also examined in this research. Surface roughness (SR)/surface topography (ST) as one of the decisive factors influencing surface finish depends, when using tools with geometrically defined cutting edges, on many factors such as geometry of the cutting wedge, cutting parameters, as well as grade, microstructure and mechanical properties of the machined work material (Grzesik, 2008). It is obviously known that from the kinematic–geometric point of view, the shape of an individual cutting edge trace, which constitutes the surface profile or surface topography, is a function of the feed rate f and the tool corner radius rε (Grzesik, 2008). On the other hand, surfaces with random distribution of peaks and valleys with substantially smaller distances between the peaks than in hard turning are generated as reported by Klocke et al. (2005) and Waikar and Guo (2008). Because of many process-induced disturbances, the shapes of irregularities within the surface profile can be distorted substantially and surfaces generated by machining operations have typically very complex shapes and textures (Griffiths, 2001). It is evident that for such cases 3D surface roughness characterisation provide more information than simple 2D approach. In practice, both 2D and 3D-SR characterisation of the surface

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Fig. 1. Three machining operations used in the technological sequences tested in this study: (a) hard turning, (b) superfinishing, and (c) ball burnishing.

profile/topography are recommended by Grzesik and Brol (2003) and Waikar and Guo (2008). Regarding these two approaches, there are a large number of papers which characterise the surface roughness of hard turned surfaces using only Ra parameter or set of height roughness parameters (Rech and Moisan, 2003) but only a few papers provide more comprehensive, multi-parameter 2D/3D descriptions of the surface roughness, often making the comparison between hard turning and grinding, as for instance Refs. Klocke et al. (2005) and Waikar and Guo (2008). In particular, Grzesik and Wanat were first to describe surfaces produced by conventional hard turning (Grzesik and Wanat, 2005) or conventional and Wiper ceramic tools (Grzesik and Wanat, 2006). Moreover, they extended these studies to the surfaces produced by partly worn ceramic tools during the tool-life period. A similar approach including the deterioration of surface finish due to the wear but CBN tools along with appropriate empirical equations for Ra, Rt and Rz height roughness parameters was presented by Yallese et al. (2009). It is reported (Luca et al., 2005) that after burnishing of a hardened steel component (64 HRC) with a ball of 6.35 mm diameter a target roughness Ra = 0.5 ␮m was obtained. In particular, when the surface which was turned with a tool of 0.8 mm nose and feed rate of ft = 0.1 mm/rev and subsequently burnished with the pressure of 38 MPa, surface roughness Ra decreased to about 0.2 ␮m. The roughness reduction expressed by the ratio of Rat/Rab (Rat-surface roughness of turned surface, Rab-surface roughness produced by

Table 1 Specifications of machining conditions. Symbol of operation

Machining operation

HT-S1 HT-S2

Hard turning with mixed ceramic tool. Conventional cutting insert – SNGN 120408 T01020. Tool geometry: rε = 0.8 mm, b = 0.1 mm, n = −20 Hard turning with mixed ceramic Wiper tool. Cutting insert-CNGA 120408 T01020 WG. Tool geometry: rε = Wiper, b = 0.1 mm, n = −20 Superfinishing after hard turning. Honing stone reference-99A320N10V

HT-W1 HT-W2

HT-S1,2 + SF HT-W1,2 + SF

HT-S2 + BUR HT-W2 + BUR

Process conditions

Ball burnishing with 3–4 passes after hard turning

HT-S1, HT-W1

vc = 150 m/min, f = 0.064 mm/rev, ap = 0.15 mm HT-S2, HT-W2 vc = 150 m/min, f = 0.21 mm/rev, ap = 0.15 mm

vc = 26 m/min, f = 0.1 mm/rev, t ≈ 45 min. Oscillation frequency-680 osc/min, applied force-40 N, amplitude 3.5 mm, grain size 29 ␮m, cooling medium: 85% kerosene and 15% machine oil Ball of 12 mm diameter, applied force 20 N, feed 0.064 mm/rev, cooling medium: 85% kerosene and 15% oil

Table 2 Surface roughness data. Machining sequence/roughness parameters HT-S1 2D roughness parameters in ␮m Rp Rv Rz Ra Rsk Rku RSm R␭q Rq [◦ ] Rq [␮m/␮m] 3D roughness parameters in ␮m Sp Sv Sz Sa Ssk

HT-S2

HT-W1

HT-W2

HT-S1 + SF HT-S2 + SF HT-W1 + SF HT-W2 + SF HT-S2 + BUR HT-W2 + BUR

1.53 3.99 0.47 0.87 0.16 1.81 2.16 0.45 0.92 0.22 3.33 6.15 0.92 1.79 0.37 0.68 1.33 0.18 0.48 0.05 −0.32 0.76 0.13 −0.11 −0.42 2.27 2.51 2.32 1.62 3.23 70.56 217.57 80.49 149.08 26.79 64.83 176.98 68.05 123.56 25.89 2.89 3.22 1.01 1.32 0.60 0.0505 0.0563 0.0177 0.0231 0.0104 1.93 2.14 4.08 0.51 1.66

3.96 3.17 7.12 1.37 1.37

0.82 0.72 1.54 0.17 1.49

1.23 1.24 2.47 0.43 1.38

0.37 0.53 0.90 0.06 1.78

0.23 0.38 0.61 0.09 −0.83 3.88 29.30 27.68 1.13 0.0197

0.17 0.21 0.38 0.05 −0.37 3.31 25.49 24.93 1.44 0.0251

0.19 0.37 0.56 0.06 −0.94 6.28 24.89 24.02 0.95 0.0165

0.22 0.25 0.47 0.08 −0.02 3.28 82.07 69.45 1.09 0.019

0.59 0.85 1.44 0.28 −0.51 2.68 132.68 105.29 1.05 0.0184

0.41 0.57 0.98 0.08 1.83

0.31 0.44 0.75 0.05 1.68

0.34 0.61 0.95 0.06 1.78

0.60 1.28 1.88 0.09 1.77

0.62 0.96 1.58 0.24 1.53

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Table 3 Measured values of bearing area parameters. Parameter/process

Rk (␮m)

Sk

Rpk (␮m)

Spk

Rvk (␮m)

Mr1 (%)

Mr2 (%)

HT-S1 HT-S2 HT-W1 HT-W2 HT-S1 + SF HT-S2 + SF HT-W1 + SF HT-W2 + SF HT-S2 + BUR HT-W2 + BUR

1.39 3.33 0.59 1.49 0.18 0.23 0.17 0.19 0.27 0.81

1.40 3.36 0.60 1.48 0.18 0.23 0.17 0.20 0.27 0.77

0.67 2.16 0.17 0.23 0.06 0.06 0.05 0.06 0.1 0.23

0.65 2.13 0.16 0.23 0.06 0.06 0.06 0.06 0.11 0.08

0.85 0.44 0.15 0.24 0.11 0.16 0.08 0.11 0.12 0.38

13.84 25.13 8.57 6.21 8.04 7.01 8.72 8.37 10.61 6.63

85.50 95.65 93.91 90.53 86.56 84.99 88.07 87.87 88.86 84.02

burnishing) is ranged from 1.4 to 2.4. In general, this improvement ranged between 40% and 90% depending on the conditions of both hard turning/milling and burnishing processes (Shiou and Hsu, 2008). In this paper, a very detailed analysis of both surface profiles and topographies was performed for machined surfaces of hardened steel parts generated by mixed ceramic tools with different geometries of the cutting tool edges. Moreover, the effects of additional finishing/smoothing operations performed subsequently on hard turned surfaces, including superfinishing and burnishing processes, were quantitatively assessed and compared which others. This is due to the fact that conventional hard machining does not produce, in many cases, surfaces with demanding service/exploitation properties including fatigue life (Guo and Yen, 2004), bearing properties (Klocke et al., 2005), rolling/sliding contact loads (Hashimoto et al., 2006), etc.

2. Experiment performance 2.1. Workpiece material, cutting tools and machining conditions Machining trials were performed on the specimens made of 41Cr4 (AISI 5140) steel with Rockwell’s hardness of 60 ± 1 HRC. Mixed ceramic cutting inserts containing 71% Al2 O3 , 28% TiC and 1% additives, commercial symbol – CC650 according to Sandvik Coromant, were used. Superfinshing passes were done using the ceramic honing stone 99A320N10V and cooling medium containing 85% kerosene and 15% machine oil. Burnishing was performed under static ball–workpiece interaction using special burnishing tool equipped with bearingizing ball and controlled spring-based pressure system to generate Fb force, as shown in Fig. 1c. Three technological operations used are schematically illustrated in Fig. 1. Moreover,

Fig. 2. Comparison of Ra and Sa values for: HT-S1 and HT-S1 + SF (1), HT-S2, HTS2 + SF and HT-S2 + BUR (2), HT-W1 and HT-W1 + SF (3), and HT-W2, HT-W2 + SF and HT-W2 + BUR (4).

process conditions for all operations performed and characteristics of the tools used are specified in Table 1. 2.2. Measurements of surface roughness Surface profiles/topographies were recorded and 2D and 3D roughness parameters were estimated by means of a TOPO01P profilometer with a diamond stylus radius of 2 ␮m. The scanned areas of 2.4 mm × 2.4 mm were selected. The sampling displacements were chosen to be x = 0.5 ␮m and y = 12.4 ␮m, respectively. 3D roughness parameters were determined on 4 elementary areas of 0.8 mm × 0.8 mm, and the obtained data were

Fig. 3. Fractions of maximum peaks and depths in the profile height: HT-S1 and HT-S1 + SF (1), HT-S2, HT-S2 + SF and HT-S2 + BUR (2), HT-W1 and HT-W1 + SF (3), and HT-W2, HT-W2 + SF and HT-W2 + BUR (4).

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with the average values of both 2D and 3D roughness parameters selected. As a result, values of the measured roughness parameters are specified in Tables 2 and 3.

3. Experimental results and discussion 3.1. Height parameters

Fig. 4. Map of normalized kurtosis (Rku) versus skewness (Rsk) for hard turning and finishing/smoothing operations.

averaged. 2D roughness parameters were estimated on the surface profile containing 3 elements of 0.8 mm length each, and the arithmetic average results were calculated taking of 200 surface profiles generated into account. The analyses performed in this paper deal

All ISO surface roughness parameters measured were clustered into 4 groups (height, spacing, hybrid and material/amplitude distribution) as proposed by Griffiths (2001) and upgraded by Grzesik (2008), were compared and analyzed. Surface roughness parameters belonging to the height and amplitude parameters are presented in Figs. 2 and 3. For these groups, some differences of values for 2D and 3D high roughness parameters including Ra, Sa, Sp, Sv and Sz were observed. The differences between Ra and Sa values (Fig. 2) are rather small and they increase from 0.01 ␮m (for example for burnished surfaces for case #1) to 0.17 ␮m (for example for HT with standard toolsHT-S1 for case #1). When Wiper tools operate with higher feed of f = 0.21 mm/rev, this difference is about 0.05 ␮m (HT-W2 for case

Fig. 5. Examples of surfaces (izometric views) for 41Cr4 steel after: HT-S1 (a), HT-W1 (b), HT-S1 + SF (c), HT-W2 + SF (d), and HT-S2 + BUR (e).

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Fig. 6. Examples of surface profiles for 41Cr4 steel after: HT-S1 (a), HT-W1 (b), HT-S1 + SF (c), HT-W2 + SF (d), HT-S2 + BUR (e), and HT-W2 + BUR (f).

#4). Minimum values of Ra and Sa parameters were measured after smoothing turning (HT-W1) with 0.064 mm/rev feed-Ra = 0.18 ␮m and subsequent superfinishing (HT-W1 + SF)-Ra = 0.05 ␮m. Fig. 3 presents the values of the Sz parameter, which is defined as SL peak to valley height, and its two components – Sp (maximum peak height on the surface) and Sv (maximum valley depth on the surface). It is evident from the bar diagrams that the participation of peaks and valleys in the total height depends distinctly on the machining process variant, as was documented previously by Grzesik et al. (2007). For instance surfaces produced by conventional HT (variant HT-S1) with feed rate of 0.064 mm/rev have lower peaks (Sp = 1.93 ␮m) but deeper valleys (Sv = 2.14 ␮m) in comparison to variant HT-S2 with large feed of 0.21 mm/rev for which peak heights increase and valley becomes deeper (the difference between Sv and Sp is about 0.79 ␮m). On the other hand, specifically for abrasive finishing (SF) and burnishing (BUR) process peaks are

reduced and valleys are somewhat deeper (Sp + Sv = 0.37 + 0.53 ␮m for HT-S1 + SF process and 0.31 + 0.44 ␮m for HT-W1 + SF, respectively). In the case of burnishing (HT-S2 + BUR variant) the ratio of Sv to Sp is about 2, which can be explained by more severe plastic deformation of peaks and lesser interference into the core material. 3.2. Amplitude distribution parameters Fig. 4 shows the plot kurtosis Rku versus skewness Rsk whose values can be positive, zero or negative. In general, different processes produce different Rsk/Rku envelopes. As can be seen in Fig. 4, surfaces with negative values of skew are produced after superfinishing and burnishing treatments of previously turned surfaces, i.e. HT-S1 (f = 0.064 mm/rev) and HT-W2 (f = 0.21 mm/rev). It should be noticed that surfaces with better bearing properties are in particular produced by additional finish abrasive passes (Rsk = −0.94 for

Fig. 7. Values of RSm parameter for: HT-S1 (1), HT-S2 (2), HT-S1 + SF (3), HT-S2 + SF (4) and HT-S2 + BUR (5), HT-W1 (6), HT-W2 (7), HT-W1 + SF (8) and HT-W2 + SF (9) and HT-W2 + BUR (10).

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Fig. 8. Illustration of modifications of turned surface profile with sharp peaks by ball burnishing: (a) HT-S2, (b) HT-W2, (c) HT-S2 + BUR, and (d) HT-W2 + BUR. Optical images of burnished lays were obtained at 60×.

HT-W2 + SF variant). In contrast, good locking surfaces are characterised by a positive skew. Like its 2D counterpart, a 3D Gaussian surface has a skew of zero (Ssk = 0). In the case study, such distributed surface can be produced by hard turning using Wiper inserts independent of feed rate (HT-W1 and HT-W2 variants) or subsequent burnishing process (HT-S2 + BUR). In general, higher negative values of Rsk correspond to values of kurtosis Rku higher than 3 (Rsk = −0.94 versus Rku = 6.27 for HT-W2 + SF variant). The lowest value of Rku = 1.62 was determined for surfaces machined with Wiper inserts and feed of f = 0.21 mm/rev (HT-W2 variant). Moreover, surfaces generated by standard inserts (variants HT-S1 and HT-S2) contain a number

of small rounded peaks and, in turn, values of Rku are below 3 (in both cases are about 2). 3.3. Surface profiles and topographies Characteristic surfaces and profiles produced by all technological sequences are illustrated in Figs. 5 and 6, respectively. Fig. 5a depicts that surfaces produced by conventional ceramic inserts contain local deeper valleys and smaller irregularities between them. On the other hand, surfaces obtained after HT + W1 process with smoothing (Wiper) inserts are depicted by quite deeper valleys.

Fig. 9. Bearing curves for 41Cr4 steel after: (a) HT-S1 (1), HT-S2 (2), HT-W1 (3), and HT-W2 (4); (b) HT-S1 + SF (A), HT-S2 + SF (B), HT-W1 + SF (C), HT-W2 + SF (D), HT-S2 + BUR (E), and HT-W2 + BUR (F).

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If the feed rate increases to f = 0.21 mm/rev machining with both standard and Wiper inserts (HT + S2 and HT + W2 variants) allow generating surfaces with regular distribution of tool nose traces, as shown in Fig. 5b. In other words, surfaces with determined structures are produced as documented previously by Grzesik and Wanat (2005). Surfaces treated by additional superfinishing (Figs. 5c and d and 6b and c) are similar to ground surfaces with numerous small peaks and characteristic lays in the form of inclined lines. Burnishing results in visible surface smoothing by plastic deformations, as for example for variant HT-S2 + BUR, as illustrated in Figs. 5e and 6f. The main difference of the surface structures modified by the combinations of HT/superfinishing and HT/burnishing processes is that after abrasive finishing final surfaces contain a number of small sharp peaks (see surface profiles in Fig. 6c and d, and topographies in Fig. 5c and d), whereas burnished surfaces are structured by visible, non-continuous, blunt ridges (see surface profile in Fig. 6e and f, and topography in Fig. 5e). It can be then concluded that burnished surfaces produced on hard parts enhance their bearing properties and reduce the running-in period in the tribological sliding pairs.

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Fig. 10. Distributions of Rpk, Rk and Rvk parameters for: 1 – HT-S1, 2 – HT-S2, 3 – HT-W1, 4 – HT-W2, 5 – HT-S1 + SF, 6 – HT-S2 + SF, 7 – HT-W1 + SF, 8 – HT-W2 + SF, 9 – HT-S2 + BUR, and 10 – HT-W2 + BUR.

3.5. Bearing area parameters 3.4. Spacing and hybrid parameters It is evident from surface profiles shown in Fig. 6 that both superfinishing and burnishing processes change the spaces between irregularities, which were generated in the turning operations, as well as their slopes. This group of roughness parameters estimated on the sample length (SL) includes the average peak spacing (Rsm), the RMS wavelength (R␭q) and the RMS slope (Rq). In general, as shown in Fig. 6a and b, MC hard turning generate profiles with regularly distributed peaks but the spacing between them is equal to the feed rate for profiles produced by conventional inserts with rounded corners (cases #1 and 2 in Figs. 7 and 8b). Profiles produced by Wiper tools indicate some discrepancies from this rule, for example for the feed of 0.21 mm/rev, the Rsm parameter is visibly lower and equal to about 150 ␮m (case #7 in Fig. 7). The next characteristic observation is that after modifications of the turned surfaces by superfinishing (Figs. 6c and d), the spacing Rsm decreases and its value is about 25–30 ␮m regardless of the previous turning operations performed (cases #3, 4 and 8, 9). The same trend was previously revealed by Grzesik et al. (2007) for hard turned surfaces treated by belt grinding. Due to the fact that the ball diameter of 12 mm is distinctly higher than the tool nose radius of 0.8 mm the profile contains more widely distributed waves (Fig. 6e and f) and the Rsm value for this case is reduced from about 220 ␮m (case #2) down to about 80 ␮m (case #5). The values of the RMS wavelength are comparable for surfaces modified by superfinishing and approximately 10–15% lower for surfaces produced by turning operations or subsequently burnished. Comparatively, the modifications of profile shapes expressed by the RMS slopes are illustrated in Fig. 8. Typical values of the RMS slopes are about Rq ∼ = 3◦ and 1◦ (1.5◦ ) for surfaces produced by hard turning with conventional and Wiper tools, respectively, which are consequently reduces down to about Rq = 1◦ or less after modifications induced by abrasion (superfinishing) and plastic deformation (multi-passing burnishing). It should be noted that both modifications do not change substantially the slope Rq in the case of surfaces turned using Wiper inserts because they do not contain so sharp peaks as surfaces produced by conventional inserts (HT-S2 versus HTW2).

Measured values of bearing area parameters are speficied in Table 3. Fig. 9a and b compares bearing curves (BACs) obtained for all machining operations considered in this study. Fig. 9a depicts that the increase of the feed for turning with standard (HT-S2) and Wiper (HT-W2) tools results in changing the shape of the BAC from S-shape (degressive–progressive) to degressive, practically linear. After SF and BUR operations surfaces are depicted by degressive–progressive BACs, as shown in Fig. 9b. Concerning the material ratio at 20% depth (Rmr(20)), it is localized at the cut c in the range of 64–69% for all hard turning operations, as shown in Fig. 9. On the other hand, additional superfinishing and burnishing improve the upper material ratio and c increase to 74% (HT-S2 + BUR variant) and 77% (HT-S2 + SF variant). However, some changes in the positioning of Rmr(20) were observed when basic hard turning operations were performed with different feeds (for example case A – c = 73% versus case B – c = 77% in Fig. 9b). It should be noticed based on data listed in Table 3 that the values of the reduced peak height are comparable for all variants containing SF operations and equal to Rpk = 0.05(6) ␮m, as presented in Fig. 10. Something higher Rpk value of 0.10 ␮m was obtained after ball-burnishing. 4. Conclusions This study allows to formulate the main following conclusions and practical recommendations: 1) The obtained results highlight the capabilities of hybrid processes, both cutting-abrasive and cutting-burnishing types, as an alternative to traditional turning and grinding operations demanding to produce high-quality hardened parts. 2) Hard turning and integrated turning-abrasive and turningburnishing technological processes produce a variety of surfaces with different geometrical and service properties. As a result, superfinishing and burnishing operations can improve surface finish and bearing properties of surfaces on hardened parts produced by conventional HT. The roughness reduction expressed by the ratio of Rat/Rab is equal to 1.71 for surfaces turned with Wiper inserts and 16.62 when standard inserts were used. It means that the improvement of the surface roughness through the ball burnishing process is about 40% and 94%, respectively.

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3) It was documented that the feed rate and insert geometry (standard versus Wiper inserts) influence the final effects concerning roughness parameters and bearing properties of the machined surfaces. In particular, better effects of burnishing were obtained for surfaces turned with conventional ceramic inserts. But in both cases the RMS slope is about 1◦ . 4) In general, HM and hybrid processes produce different Rsk/Rku envelopes, which allow to select the desired process conditions in order to produce surfaces with desired bearing or locking properties. Moreover, the reduced peak height Rpk, which represents the material portion in the vicinity of peaks being removed during sliding interactions, can be minimized up to 0.05. So, the running-in period can be shortened as much as possible. References Davim, J.P. (Ed.), 2009. Machining of Hard Materials. Springer, London. Ding, H., Shin, Y.C., 2010. Laser-assisted machining of hardened steel parts with surface integrity analysis. Int. J. Mach. Tools Manuf. 50, 106–114. Garcia Navas, V., Garcia-Rosales, C., Gil Sevilliano, J., Ferreres, I., 2008. Hard turning plus grinding-a combination to obtain good surface integrity in AISI 01 tool steel machined parts. Mach. Sci. Technol. 12, 15–32. Griffiths, B., 2001. Manufacturing Surface Technology. Penton Press, London. Grzesik, W., Brol, S., 2003. Hybrid approach to surface roughness evaluation in multistage machining processes. J. Mater. Process. Technol. 134, 265–272. Grzesik, W., Wanat, T., 2005. Comparative assessment of surface roughness produced by hard machining with mixed ceramic tools including 2D and 3D analysis. J. Mater. Process. Technol. 169, 364–371.

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