- Email: [email protected]
Effects of amplitude and frequency on the wear mode change of Inconel 690 SG tube mated with SUS 409
Wear 313 (2014) 83–88
Contents lists available at ScienceDirect
Wear journal homepage: www.elsevier.com/locate/wear
Effects of amplitude and frequency on the wear mode change of Inconel 690 SG tube mated with SUS 409 Jae Yong Yun, Myung Chul Park, Gyeong Su Shin, Ji Haeng Heo, Dae Il Kim, Seon Jin Kim n Division of Materials Science and Engineering, Hanyang University, Seoul 133-791, Korea
art ic l e i nf o
a b s t r a c t
Article history: Received 16 November 2013 Received in revised form 26 February 2014 Accepted 26 February 2014 Available online 5 March 2014
Steam generator (SG) tubes in certain types of nuclear power plants experience flow-induced vibrations that can result in fretting wear. The wear mode under these conditions can change with wear variables. Using a custom-designed fretting test apparatus, the effects of amplitude and frequency on wear mode changes for Inconel 690 SG tubes mated with SUS 409 were investigated. Changes in the wear mode were found by using periodic measurements of weight loss to calculate wear coefficients. The wear mode was observed to change from stick to gross slip and sliding as amplitude increased from 25 μm to 300 μm. However, the wear mode did not change with increasing frequency or testing duration within the range of applied conditions. & 2014 Elsevier B.V. All rights reserved.
Keywords: Fretting Sliding wear Inconel 690 Steam generator Wear coefficient
1. Introduction It is well known that steam generator tubes, Inconel 600 and 690, experience flow-induced vibration in a nuclear power plant [1,2]. During heat exchange, fretting wear can occur between the tube and anti-vibration structures such as SUS 405SS and SUS 409SS. Since the wear damage on the tube can cause filling up of the tube and reduction of SG thermal exchange efficiency in nuclear power plants [3], investigation on the wear mode change and wear coefficient is necessary. The amount of wear damage varies with position of the tube in the steam generator because wear variables, such as amplitude and frequency, vary with different local flow speeds [4]. This change of wear variables leads to changes in the wear mode. The wear mode is generally categorized into two parts: fretting wear and sliding wear and more specifically into four parts: stick, mixed stick–slip, gross slip, and sliding [5–7]. Amplitude is considered as a main variable in wear mode change [8–11]. The fretting-to-sliding wear transition amplitude differs by a report. In general, transition amplitude is in the range of 100 to 300 μm [5,12]. However, many studies about wear behavior of Inconel 600 or 690 had difficulty in observing the wear mode change because the testing was conducted at an amplitude less than 100 μm. Frequency is also an important variable in the wear mode [5,13,14]. With increasing frequency, wear rate increases due to
n
Corresponding author. Tel.: þ 82 2 22200406; fax: þ82 22937844. E-mail address: [email protected] (S.J. Kim).
http://dx.doi.org/10.1016/j.wear.2014.02.019 0043-1648 & 2014 Elsevier B.V. All rights reserved.
increased interfacial strain rate and temperature [14]. Surface crack nucleation and growth also accelerate with increasing strain rate [5]. Although most of the vibration frequencies of steam generator tubes are reported as higher than 30 Hz [7,15], many researchers have conducted wear tests at frequency less than 30 Hz. Therefore, in this paper we investigated the changes of the wear mode and wear coefficient in an amplitude range of 25 to 300 μm and a frequency range of 10 to 60 Hz under a normal load of 100 N. Because increase in the contact area can cause decrease in the wear rate [3], a wear test was conducted under constant
Fig. 1. Schematic of fretting wear test apparatus.
84
J.Y. Yun et al. / Wear 313 (2014) 83–88
Table 1 Chemical composition of Inconel 690TT and SUS 409SS. Specimen
Inconel 690TT SUS 409SS
Element Ni
Fe
Cr
Co
C
Si
Mn
Ti
S
Bal 0.310
10.810 Bal
28.542 11.7
0.030 –
0.030 0.015
0.176 0.654
0.092 0.215
0.330 0.128
– 0.028
Fig. 2. Microstructure of (a) Inconel 690 and (b) SUS 409.
Fig. 3. Weight loss as a function of fretting distance under a normal load of 100 N. (a) Fretting wear distance up to 550,000 m. (b) Fretting wear distance up to 50,000 m.
J.Y. Yun et al. / Wear 313 (2014) 83–88
contact area and stress to investigate the sole effects of amplitude and frequency on wear mode change. 2. Experimental procedure A commercialized Inconel 690TT tube made by Sandvik was used for the fretting wear test. SUS 409SS, which is generally used for anti-vibration structures in steam generators, was used as a mating material. As shown in Fig. 1, the tube surface is machined into a rectangular shape (5 mm 20 mm) to make constant contact stress during the test. Table 1 shows the chemical compositions of Inconel 690 and SUS 409 measured by Optical Emission Spectroscopy. Fig. 2 shows the microstructures of commercial Inconel 690 and SUS 409 corresponding to typical microstructure of the alloys. Under a normal load of 100 N, the fretting wear test was performed with increasing amplitude from 25 to 300 μm and frequency from 10 to 60 Hz at room temperature in an air environment. Although the normal load of 100 N is higher than the peak force between the tube and support plates [8], the stress in this research is much less than the peak stress even under the same normal load of 100 N because of the large contact area. Weight losses were measured at every 15, 30, 60 and 120 min. More than three replicate tests were performed to obtain reliable data. The relative deviation of the amount of wear loss between tests was about 7 10%. The test durations and the test distances were determined to cover the test range in others [1–3] to be comparable. The wear coefficient, K, of the Archard equation was calculated from weight loss data. Scanning electron microscopy (SEM) was utilized for surface microscopy and wear mode analysis.
85
3. Results and discussion Fig. 3 shows the effect of distance on the fretting wear behavior. Weight loss was drawn as a function of test distance under an amplitude of 25–300 μm and a frequency of 10–60 Hz. In other research, researchers suggested a hypothesis that increase in contact area and decrease in contact stress caused decrease in the wear rate [3]. However, in this study, weight loss increased linearly in all test specimens, as shown in Fig. 3. In other words, wear coefficient did not change with increasing distance. The slope of weight loss increased with increasing amplitude at fixed frequency. In contrast, the slope did not change with increasing frequency at fixed amplitude. This indicates that the wear coefficient and wear mode are more likely to be affected by amplitude than frequency. To quantitatively analyze this result, wear coefficients were calculated using the Archard equation.
Fig. 4. Wear coefficient as a function of fretting amplitude.
Fig. 5. Wear coefficient as a function of fretting frequency.
Fig. 6. SEM images of worn surfaces at (a) 25 μm amplitude, 10 Hz frequency, (b) 25 μm amplitude, 30 Hz frequency, and (c) 25 μm amplitude, 60 Hz frequency.
86
J.Y. Yun et al. / Wear 313 (2014) 83–88
In the prediction of wear behavior using the Archard equation shown in Eq. (1), the wear coefficient, K, is assumed to be constant, and the wear volume is linearly proportional to the sliding distance and normal load V ¼ KFS
ð1Þ
where V is wear volume, F is applied normal load, K is wear coefficient, and S is sliding distance. In some cases, the wear coefficient may possibly change with changing material properties such as hardness due to strain hardening during test. However, as shown in Fig. 4, the wear coefficient, K, increased with increasing amplitude. This indicates that the wear coefficient and so wear mode are likely affected by amplitude, as mentioned above. As shown in Fig. 5, the wear coefficient, K, was similar under the same frequency conditions. The least square fitted lines match the data points and are nearly parallel to the x-axis, indicating that the wear coefficient and wear mode are likely unaffected by frequency, as mentioned before. The morphologies of worn surfaces were similar at the same amplitude, as shown in Figs. 6–9.
Fig. 8. SEM images of worn surfaces at (a) 150 μm amplitude, 10 Hz frequency, (b) 150 μm amplitude, 30 Hz frequency, and (c) 150 μm amplitude, 60 Hz frequency.
Fig. 7. SEM images of worn surfaces at (a) 50 μm amplitude, 10 Hz frequency, (b) 50 μm amplitude, 30 Hz frequency, and (c) 50 μm amplitude, 60 Hz frequency.
The wear coefficient, at amplitude of 25 μm, is nearly 0. It is considered to be due to stick. It is well known that stick phenomenon occurs under high normal load and relatively low amplitude [5]. In observation of worn surfaces under SEM, the stick phenomenon was observed in regions with very small wear damage as shown in Fig. 6. The wear coefficient increased rapidly with increasing amplitude from 25 to 50 μm. It has been reported that the rapid increase of wear coefficient indicates the change in the wear mode in many reports [5,16,17]. In observation of worn surfaces under SEM, the mixed stick and slip phenomenon was observed along with crack formation on a plastically disturbed layer produced by fretting fatigue at constant amplitude of 50 μm, as shown in Fig. 7. There was also no evident material transfer or formation since the wear damage on the tube can cause filling up of wear debris due to the relatively low amplitude in this region. And the wear coefficient mildly increases with increasing amplitude from 50 μm, indicating that the wear mode is gross slip in this region [5,17]. In observation of worn surfaces under
J.Y. Yun et al. / Wear 313 (2014) 83–88
87
frequency. This change in the wear mode corroborates the changes in wear coefficient shown in Figs. 4 and 5. The result further indicates that the wear mode changes with amplitude but not with frequency.
4. Summary 1. Fretting wear test was conducted on an Inconel 690 tube mated with SUS 409 and change in the wear mode was observed. It was found that the wear mode changed from stick to mixed stick and slip, gross slip, and sliding with increasing amplitude from 25 μm to 300 μm. 2. The wear mode change of Inconel 690 tube was not found with increasing frequency from 10 Hz to 60 Hz in the test region. Calculation of wear coefficient through Archard equation and observation of worn surface is conducted to demonstrate the wear mode change. The stick phenomenon was observed at an amplitude of 25 μm. The wear coefficient and weight loss were nearly 0. At an amplitude of 50 μm, mixed stick and slip phenomenon was observed, and the wear coefficient and weight loss increased rapidly to about 9 10 14 m3/N m. At an amplitude of 150 μm, the gross slip phenomenon was observed, and the wear coefficient and weight loss increased gradually. At amplitude of 300 μm, a partial sliding phenomenon was observed, and the wear coefficient increased gradually to about 1.7 10 13 m3/N m.
Acknowledgments This research was supported by the Human Resource Development Project of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korean government Ministry of Knowledge Economy (No. 20114010203020). This research was also supported by the Nuclear Research & Development of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by Korean government Ministry of Knowledge Economy (No. 20111510100060) References
Fig. 9. SEM images of worn surfaces at (a) 300 μm amplitude, 10 Hz frequency, (b) 300 μm amplitude, 30 Hz frequency, and (c) 300 μm amplitude, 60 Hz frequency.
SEM, the gross slip phenomenon was observed in a wave pattern at constant amplitude of 150 μm, as shown in Fig. 8. This wave pattern occurred because the amplitude was high enough to generate plastic deformation. It is reported that the constant value of wear coefficient indicates reciprocating sliding wear condition [5]. In Fig. 4, the wear coefficient is not saturated in this test region. However in observation of worn surfaces under SEM, a partial sliding wear phenomenon with partial reciprocating scratch marks was observed at a constant amplitude of 300 μm, as shown in Fig. 9. After wear test, specimens exhibited significant wear debris, implying that the amplitude was high enough to create wear debris out of the wear track. These results indicate that a frettingto-sliding wear transition occurs at the amplitude of 300 μm, and the only partial sliding wear, not fully sliding, occurs in this test region. Figs. 6–9 show that the morphology of worn surfaces changes from stick to mixed stick and slip, gross slip, and sliding with increasing amplitude, but does not change with increasing
[1] S.-H. Jeong, C.-W. Cho, Y.-Z. Lee, Friction and wear of Inconel 690 for steam generator tube in elevated temperature water under fretting condition, Tribol. Int. 38 (3) (2005) 283–288. [2] M.-K. Lim, S.-D. Oh, Y.-Z. Lee, Friction and wear of Inconel 690 and Inconel 600 for steam generator tube in room temperature water, Nucl. Eng. Des. 226 (2) (2003) 97–105. [3] G.S. Park, G.G. Kim, S.J. Kim, Sliding wear behaviors of steam generator tube materials in high temperature water environment, J. Nucl. Mater. 352 (1–3) (2006) 80–84. [4] C.-Y. Park, K.-W. Ryu, H. Rhee, Development of a computer program to predict structural integrity against fretting wear of steam generator tubes: PIAT (program for integrity assessment of steam generator tubes), Nucl. Eng. Des. 257 (2013) 146–154. [5] O. Vingsbo, S. Söderberg, On fretting maps, Wear 126 (2) (1988) 131–147. [6] Z.R. Zhou, et al., Progress in fretting maps, Tribol. Int. 39 (10) (2006) 1068–1073. [7] D.-G. Kim, Y.-Z. Lee, Experimental investigation on sliding and fretting wear of steam generator tube materials, Wear 250 (1–12) (2001) 673–680. [8] I. Chung, M. Lee, An experimental study on fretting wear behavior of crosscontacting Inconel 690 tubes, Nucl. Eng. Des. 241 (10) (2011) 4103–4110. [9] T.-H. Kim, S.-S. Kim, Fretting wear mechanisms of Zircaloy-4 and Inconel 600 contact in air, KSME Int. J. 15 (9) (2001) 1274–1280. [10] K.H. Cho, T.H. Kim, S.S. Kim, Fretting wear characteristics of Zircaloy-4 tube, Wear 219 (1) (1998) 3–7. [11] Y.-H. Lee, I.-S. Kim, S.-S. Kang, H.-D. Chung, A study on wear coefficients and mechanisms of steam generator tube materials, Wear 250 (1–12) (2001) 718–725. [12] G.X. Chen, Z.R. Zhou, Study on transition between fretting and reciprocating sliding wear, Wear 250 (1–12) (2001) 665–672. [13] L. Li, I. Etsion, F.E. Talke, The effect of frequency on fretting in a micro-spherical contact, Wear 270 (11–12) (2011) 857–865.
88
J.Y. Yun et al. / Wear 313 (2014) 83–88
[14] S. Söderberg, U. Bryggman, T. McCullough, Frequency effects in fretting wear, Wear 110 (1) (1986) 19–34. [15] H. Rhee, M.H. Boo, C.Y. Park, K.W. Ryu, Development and application of an efficient method for performing modal analysis of steam generator tubes in nuclear power plants, Nucl. Eng. Des. 240 (10) (2010) 3669–3676.
[16] S. Söderberg, S. Nikoonezhad, K. Salama, O. Vingsbo, Accelerated fretting wear testing using ultrasonics, Ultrasonics 24 (6) (1986) 348–353. [17] T. Kayaba, A. Iwabuchi, On the effects of slip amplitude on fretting wear, Technol. Rep. Tohoku Univ. 44 (2) (1979) 603–623.
Contents lists available at ScienceDirect
Wear journal homepage: www.elsevier.com/locate/wear
Effects of amplitude and frequency on the wear mode change of Inconel 690 SG tube mated with SUS 409 Jae Yong Yun, Myung Chul Park, Gyeong Su Shin, Ji Haeng Heo, Dae Il Kim, Seon Jin Kim n Division of Materials Science and Engineering, Hanyang University, Seoul 133-791, Korea
art ic l e i nf o
a b s t r a c t
Article history: Received 16 November 2013 Received in revised form 26 February 2014 Accepted 26 February 2014 Available online 5 March 2014
Steam generator (SG) tubes in certain types of nuclear power plants experience flow-induced vibrations that can result in fretting wear. The wear mode under these conditions can change with wear variables. Using a custom-designed fretting test apparatus, the effects of amplitude and frequency on wear mode changes for Inconel 690 SG tubes mated with SUS 409 were investigated. Changes in the wear mode were found by using periodic measurements of weight loss to calculate wear coefficients. The wear mode was observed to change from stick to gross slip and sliding as amplitude increased from 25 μm to 300 μm. However, the wear mode did not change with increasing frequency or testing duration within the range of applied conditions. & 2014 Elsevier B.V. All rights reserved.
Keywords: Fretting Sliding wear Inconel 690 Steam generator Wear coefficient
1. Introduction It is well known that steam generator tubes, Inconel 600 and 690, experience flow-induced vibration in a nuclear power plant [1,2]. During heat exchange, fretting wear can occur between the tube and anti-vibration structures such as SUS 405SS and SUS 409SS. Since the wear damage on the tube can cause filling up of the tube and reduction of SG thermal exchange efficiency in nuclear power plants [3], investigation on the wear mode change and wear coefficient is necessary. The amount of wear damage varies with position of the tube in the steam generator because wear variables, such as amplitude and frequency, vary with different local flow speeds [4]. This change of wear variables leads to changes in the wear mode. The wear mode is generally categorized into two parts: fretting wear and sliding wear and more specifically into four parts: stick, mixed stick–slip, gross slip, and sliding [5–7]. Amplitude is considered as a main variable in wear mode change [8–11]. The fretting-to-sliding wear transition amplitude differs by a report. In general, transition amplitude is in the range of 100 to 300 μm [5,12]. However, many studies about wear behavior of Inconel 600 or 690 had difficulty in observing the wear mode change because the testing was conducted at an amplitude less than 100 μm. Frequency is also an important variable in the wear mode [5,13,14]. With increasing frequency, wear rate increases due to
n
Corresponding author. Tel.: þ 82 2 22200406; fax: þ82 22937844. E-mail address: [email protected] (S.J. Kim).
http://dx.doi.org/10.1016/j.wear.2014.02.019 0043-1648 & 2014 Elsevier B.V. All rights reserved.
increased interfacial strain rate and temperature [14]. Surface crack nucleation and growth also accelerate with increasing strain rate [5]. Although most of the vibration frequencies of steam generator tubes are reported as higher than 30 Hz [7,15], many researchers have conducted wear tests at frequency less than 30 Hz. Therefore, in this paper we investigated the changes of the wear mode and wear coefficient in an amplitude range of 25 to 300 μm and a frequency range of 10 to 60 Hz under a normal load of 100 N. Because increase in the contact area can cause decrease in the wear rate [3], a wear test was conducted under constant
Fig. 1. Schematic of fretting wear test apparatus.
84
J.Y. Yun et al. / Wear 313 (2014) 83–88
Table 1 Chemical composition of Inconel 690TT and SUS 409SS. Specimen
Inconel 690TT SUS 409SS
Element Ni
Fe
Cr
Co
C
Si
Mn
Ti
S
Bal 0.310
10.810 Bal
28.542 11.7
0.030 –
0.030 0.015
0.176 0.654
0.092 0.215
0.330 0.128
– 0.028
Fig. 2. Microstructure of (a) Inconel 690 and (b) SUS 409.
Fig. 3. Weight loss as a function of fretting distance under a normal load of 100 N. (a) Fretting wear distance up to 550,000 m. (b) Fretting wear distance up to 50,000 m.
J.Y. Yun et al. / Wear 313 (2014) 83–88
contact area and stress to investigate the sole effects of amplitude and frequency on wear mode change. 2. Experimental procedure A commercialized Inconel 690TT tube made by Sandvik was used for the fretting wear test. SUS 409SS, which is generally used for anti-vibration structures in steam generators, was used as a mating material. As shown in Fig. 1, the tube surface is machined into a rectangular shape (5 mm 20 mm) to make constant contact stress during the test. Table 1 shows the chemical compositions of Inconel 690 and SUS 409 measured by Optical Emission Spectroscopy. Fig. 2 shows the microstructures of commercial Inconel 690 and SUS 409 corresponding to typical microstructure of the alloys. Under a normal load of 100 N, the fretting wear test was performed with increasing amplitude from 25 to 300 μm and frequency from 10 to 60 Hz at room temperature in an air environment. Although the normal load of 100 N is higher than the peak force between the tube and support plates [8], the stress in this research is much less than the peak stress even under the same normal load of 100 N because of the large contact area. Weight losses were measured at every 15, 30, 60 and 120 min. More than three replicate tests were performed to obtain reliable data. The relative deviation of the amount of wear loss between tests was about 7 10%. The test durations and the test distances were determined to cover the test range in others [1–3] to be comparable. The wear coefficient, K, of the Archard equation was calculated from weight loss data. Scanning electron microscopy (SEM) was utilized for surface microscopy and wear mode analysis.
85
3. Results and discussion Fig. 3 shows the effect of distance on the fretting wear behavior. Weight loss was drawn as a function of test distance under an amplitude of 25–300 μm and a frequency of 10–60 Hz. In other research, researchers suggested a hypothesis that increase in contact area and decrease in contact stress caused decrease in the wear rate [3]. However, in this study, weight loss increased linearly in all test specimens, as shown in Fig. 3. In other words, wear coefficient did not change with increasing distance. The slope of weight loss increased with increasing amplitude at fixed frequency. In contrast, the slope did not change with increasing frequency at fixed amplitude. This indicates that the wear coefficient and wear mode are more likely to be affected by amplitude than frequency. To quantitatively analyze this result, wear coefficients were calculated using the Archard equation.
Fig. 4. Wear coefficient as a function of fretting amplitude.
Fig. 5. Wear coefficient as a function of fretting frequency.
Fig. 6. SEM images of worn surfaces at (a) 25 μm amplitude, 10 Hz frequency, (b) 25 μm amplitude, 30 Hz frequency, and (c) 25 μm amplitude, 60 Hz frequency.
86
J.Y. Yun et al. / Wear 313 (2014) 83–88
In the prediction of wear behavior using the Archard equation shown in Eq. (1), the wear coefficient, K, is assumed to be constant, and the wear volume is linearly proportional to the sliding distance and normal load V ¼ KFS
ð1Þ
where V is wear volume, F is applied normal load, K is wear coefficient, and S is sliding distance. In some cases, the wear coefficient may possibly change with changing material properties such as hardness due to strain hardening during test. However, as shown in Fig. 4, the wear coefficient, K, increased with increasing amplitude. This indicates that the wear coefficient and so wear mode are likely affected by amplitude, as mentioned above. As shown in Fig. 5, the wear coefficient, K, was similar under the same frequency conditions. The least square fitted lines match the data points and are nearly parallel to the x-axis, indicating that the wear coefficient and wear mode are likely unaffected by frequency, as mentioned before. The morphologies of worn surfaces were similar at the same amplitude, as shown in Figs. 6–9.
Fig. 8. SEM images of worn surfaces at (a) 150 μm amplitude, 10 Hz frequency, (b) 150 μm amplitude, 30 Hz frequency, and (c) 150 μm amplitude, 60 Hz frequency.
Fig. 7. SEM images of worn surfaces at (a) 50 μm amplitude, 10 Hz frequency, (b) 50 μm amplitude, 30 Hz frequency, and (c) 50 μm amplitude, 60 Hz frequency.
The wear coefficient, at amplitude of 25 μm, is nearly 0. It is considered to be due to stick. It is well known that stick phenomenon occurs under high normal load and relatively low amplitude [5]. In observation of worn surfaces under SEM, the stick phenomenon was observed in regions with very small wear damage as shown in Fig. 6. The wear coefficient increased rapidly with increasing amplitude from 25 to 50 μm. It has been reported that the rapid increase of wear coefficient indicates the change in the wear mode in many reports [5,16,17]. In observation of worn surfaces under SEM, the mixed stick and slip phenomenon was observed along with crack formation on a plastically disturbed layer produced by fretting fatigue at constant amplitude of 50 μm, as shown in Fig. 7. There was also no evident material transfer or formation since the wear damage on the tube can cause filling up of wear debris due to the relatively low amplitude in this region. And the wear coefficient mildly increases with increasing amplitude from 50 μm, indicating that the wear mode is gross slip in this region [5,17]. In observation of worn surfaces under
J.Y. Yun et al. / Wear 313 (2014) 83–88
87
frequency. This change in the wear mode corroborates the changes in wear coefficient shown in Figs. 4 and 5. The result further indicates that the wear mode changes with amplitude but not with frequency.
4. Summary 1. Fretting wear test was conducted on an Inconel 690 tube mated with SUS 409 and change in the wear mode was observed. It was found that the wear mode changed from stick to mixed stick and slip, gross slip, and sliding with increasing amplitude from 25 μm to 300 μm. 2. The wear mode change of Inconel 690 tube was not found with increasing frequency from 10 Hz to 60 Hz in the test region. Calculation of wear coefficient through Archard equation and observation of worn surface is conducted to demonstrate the wear mode change. The stick phenomenon was observed at an amplitude of 25 μm. The wear coefficient and weight loss were nearly 0. At an amplitude of 50 μm, mixed stick and slip phenomenon was observed, and the wear coefficient and weight loss increased rapidly to about 9 10 14 m3/N m. At an amplitude of 150 μm, the gross slip phenomenon was observed, and the wear coefficient and weight loss increased gradually. At amplitude of 300 μm, a partial sliding phenomenon was observed, and the wear coefficient increased gradually to about 1.7 10 13 m3/N m.
Acknowledgments This research was supported by the Human Resource Development Project of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korean government Ministry of Knowledge Economy (No. 20114010203020). This research was also supported by the Nuclear Research & Development of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by Korean government Ministry of Knowledge Economy (No. 20111510100060) References
Fig. 9. SEM images of worn surfaces at (a) 300 μm amplitude, 10 Hz frequency, (b) 300 μm amplitude, 30 Hz frequency, and (c) 300 μm amplitude, 60 Hz frequency.
SEM, the gross slip phenomenon was observed in a wave pattern at constant amplitude of 150 μm, as shown in Fig. 8. This wave pattern occurred because the amplitude was high enough to generate plastic deformation. It is reported that the constant value of wear coefficient indicates reciprocating sliding wear condition [5]. In Fig. 4, the wear coefficient is not saturated in this test region. However in observation of worn surfaces under SEM, a partial sliding wear phenomenon with partial reciprocating scratch marks was observed at a constant amplitude of 300 μm, as shown in Fig. 9. After wear test, specimens exhibited significant wear debris, implying that the amplitude was high enough to create wear debris out of the wear track. These results indicate that a frettingto-sliding wear transition occurs at the amplitude of 300 μm, and the only partial sliding wear, not fully sliding, occurs in this test region. Figs. 6–9 show that the morphology of worn surfaces changes from stick to mixed stick and slip, gross slip, and sliding with increasing amplitude, but does not change with increasing
[1] S.-H. Jeong, C.-W. Cho, Y.-Z. Lee, Friction and wear of Inconel 690 for steam generator tube in elevated temperature water under fretting condition, Tribol. Int. 38 (3) (2005) 283–288. [2] M.-K. Lim, S.-D. Oh, Y.-Z. Lee, Friction and wear of Inconel 690 and Inconel 600 for steam generator tube in room temperature water, Nucl. Eng. Des. 226 (2) (2003) 97–105. [3] G.S. Park, G.G. Kim, S.J. Kim, Sliding wear behaviors of steam generator tube materials in high temperature water environment, J. Nucl. Mater. 352 (1–3) (2006) 80–84. [4] C.-Y. Park, K.-W. Ryu, H. Rhee, Development of a computer program to predict structural integrity against fretting wear of steam generator tubes: PIAT (program for integrity assessment of steam generator tubes), Nucl. Eng. Des. 257 (2013) 146–154. [5] O. Vingsbo, S. Söderberg, On fretting maps, Wear 126 (2) (1988) 131–147. [6] Z.R. Zhou, et al., Progress in fretting maps, Tribol. Int. 39 (10) (2006) 1068–1073. [7] D.-G. Kim, Y.-Z. Lee, Experimental investigation on sliding and fretting wear of steam generator tube materials, Wear 250 (1–12) (2001) 673–680. [8] I. Chung, M. Lee, An experimental study on fretting wear behavior of crosscontacting Inconel 690 tubes, Nucl. Eng. Des. 241 (10) (2011) 4103–4110. [9] T.-H. Kim, S.-S. Kim, Fretting wear mechanisms of Zircaloy-4 and Inconel 600 contact in air, KSME Int. J. 15 (9) (2001) 1274–1280. [10] K.H. Cho, T.H. Kim, S.S. Kim, Fretting wear characteristics of Zircaloy-4 tube, Wear 219 (1) (1998) 3–7. [11] Y.-H. Lee, I.-S. Kim, S.-S. Kang, H.-D. Chung, A study on wear coefficients and mechanisms of steam generator tube materials, Wear 250 (1–12) (2001) 718–725. [12] G.X. Chen, Z.R. Zhou, Study on transition between fretting and reciprocating sliding wear, Wear 250 (1–12) (2001) 665–672. [13] L. Li, I. Etsion, F.E. Talke, The effect of frequency on fretting in a micro-spherical contact, Wear 270 (11–12) (2011) 857–865.
88
J.Y. Yun et al. / Wear 313 (2014) 83–88
[14] S. Söderberg, U. Bryggman, T. McCullough, Frequency effects in fretting wear, Wear 110 (1) (1986) 19–34. [15] H. Rhee, M.H. Boo, C.Y. Park, K.W. Ryu, Development and application of an efficient method for performing modal analysis of steam generator tubes in nuclear power plants, Nucl. Eng. Des. 240 (10) (2010) 3669–3676.
[16] S. Söderberg, S. Nikoonezhad, K. Salama, O. Vingsbo, Accelerated fretting wear testing using ultrasonics, Ultrasonics 24 (6) (1986) 348–353. [17] T. Kayaba, A. Iwabuchi, On the effects of slip amplitude on fretting wear, Technol. Rep. Tohoku Univ. 44 (2) (1979) 603–623.