- Email: [email protected]
The influence of glow discharge nitriding, oxynitriding and carbonitriding on surface modification of Ti–1Al–1Mn titanium alloy
Vacuum 64 (2002) 41–46
The influence of glow discharge nitriding, oxynitriding and carbonitriding on surface modification of Ti–1Al–1Mn titanium alloy J.R. Sobiecki*, T. Wierzchon! , J. Rudnicki Faculty of Materials Science and Engineering, Warsaw University of Technology, 02-507 Warsaw, Wołoska 141, Poland Received 7 March 2001; accepted 8 May 2001
Abstract Recent surface treatment studies show that titanium alloys should have an improved resistance to frictional wear and fatigue strength limit without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface nitrided, oxynitrided and carbonitrided diffusion layers. This paper presents the results of metallographic examinations, corrosion and wear resistance tests, surface chemical composition investigation, as well as rotating and bending fatigue tests. These surface treatments increase the useful properties of the titanium alloy. The influence of treatment time and the thickness of the layers on its properties are also investigated. r 2001 Elsevier Science Ltd. All rights reserved. Keywords: Plasma nitriding; Oxynitriding; Carbonitriding; Titanium alloy; Wear and corrosion resistance; Chemical composition; Fatigue strength
1. Introduction Titanium and its alloys have many attractive properties including high specific strength and modulus, excellent corrosion resistance, and, in some cases, excellent cryogenic properties [1]. They are widely used in aerospace applications and many corrosive environments. However, titanium alloys have found little use in general engineering application, mainly because of their poor tribological properties, such as poor abrasive and adhesive wear resistance, a tendency to galling and seizure, a tendency to fretting wear and *Corresponding author. Fax: +48-33-660-8514. E-mail address: [email protected] (J.R. Sobiecki).
fretting fatigue, and high coefficients of friction [2]. In order to improve such surface properties a variety of surface engineering techniques, such as gas nitriding [3–5], plasma nitriding [6–8], laser nitriding [3,9–11], and ion implantation [12,13] have been successfully applied. However, it has also been found that such treatments lead to a decrease of fatigue strength in titanium alloys [3,11]. As the reasons for the reduction in fatigue strength have not been made clear, it is necessary to study systematically the fatigue behaviour of surface-treated materials in pure titanium and titanium alloys. Among the methods with most potential are glow discharge assisted techniques, which permit control of the layer formation process as regards both the structure and the
0042-207X/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 2 - 2 0 7 X ( 0 1 ) 0 0 3 7 3 - 6
42
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
phase composition and, thus modify the properties of the layers. The present paper describes a modification of the plasma discharge nitriding treatment of titanium a alloy, i.e. glow discharge assisted oxynitriding and carbonitriding introducing oxygen or carbon into the surface zone to form a TiON or TiCN layer.
2. Experimental methods The specimens were made of titanium alpha alloy (1–2.5%Al, 0.7–2.0%Mn Ti in balance). The process was carried out in a universal apparatus for different types of thermo-chemical treatment under glow discharge conditions [14]. The DC power supply was used. During the process, the voltage was 800 V and the current was 5 A. The samples were subjected to plasma nitriding at a temperature of 8001C in a nitrogen atmosphere, plasma oxynitriding at the same temperature in nitrogen and air (the volume percentage of air content was 2%) and plasma carbonitriding also at 8001C in nitrogen and methane atmosphere (the volume percentage of methane was 15%). The pressure in the reactor chamber was about 4 hPa. The time of the treatment was 3, 6 and 12 h. The metallographic examination was made using a Neophot microscope on previously etched samples in a solution of chemical composition: 96 cm3 H2O+2 cm3 HNO3+2 cm3 HF. The microhardness of the layer was measured by a Hanneman unit connected with the same microscope, and the load was 50 g. The corrosion resistance was measured in a 0.5 M NaCl solution by the potentiodynamic method using the Atlas–Sollich computerized equipment designed for electrochemical examinations. The polarization curves were determined by polarizing the samples from a potential of 1000 mV towards anodic potentials, at a potential varying rate of 50 mV/min. Prior to the measurements, the samples were kept in the test solution for 24 h. The potential was measured with respect to a calomel electrode (SCE). The frictional wear resistance was measured using the ‘‘three rollers+taper method’’ [15]. In this test, friction is applied under specified conditions, between three fixed cylindrical specimens (rollers)
8 mm in diameter, covered with surface layers, and a rotating conical counter-specimen (taper). The linear wear expressed as the wear depth was determined by measuring the diameters of ellipses formed on the surfaces of each roller. The results were then averaged. The counter specimen was made of SW7M high speed steel quenched and tempered to a hardness of 64 HRC. Constant unit loads of 200 and 400 MPa were applied. The phase composition of the layers was determined using a Philips PW 1830 X-ray diffractometer using a CoKa source. The chemical composition of the layers was analysed using the EDS unit fitted to the LEO 1530 microscope. The fatigue behaviour was examined in a fatigue testing machine (bending rotation) at a constant bending moment and a rotational speed of 2200 rotations per minute. The fatigue strength was determined in 24 samples. The samples were loaded using the step method with the stress variation increment s=0.5 kg/mm2 (ca. 5 MPa). The results were compared with those obtained for the Ti–1Al–1Mn alloy annealed at a temperature of 8001C for 3 h.
3. Results Fig. 1 shows the microstructures of the surface layers formed on the Ti–1Al–1Mn titanium alloy obtained after different thermo-chemical treatments. The time of treatment was 3 h. Microstructures obtained following the 12 h of treatment are presented in Fig. 2. The layers produced during 3 h of treatment are about 15 mm thick. The plasma oxynitriding produced the layers which had the highest thickness (about 25 mm). Increasing the time to 12 h also increases the thickness of the layer to 25 mm for the nitriding and carbonitriding processes and to 35 mm for oxynitrided layers. The increased thickness of the oxynitrided layers can be explained by the higher speed of diffusion of oxygen into the titanium substrate. The surface microhardness of the layers are independent of the time of the process. They range from 1850 HV0.05 for the oxynitrided layers to 2100 HV0.05 for the nitrided layers and 2240 HV0.05 for the carbonitrided layers.
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
43
Fig. 1. Microstructures of the surface layers formed on titanium alloy during (a) nitriding, (b) oxynitriding and (c) carbonitriding after 3 h of treatment.
Fig. 2. Microstructures of the surface layers formed on titanium alloy during (a) nitriding, (b) oxynitriding and (c) carbonitriding after 12 h of treatment.
The surface chemical compositions of the layers obtained during 12 h processes are summarized in Table 1. As one can see from Table 1, in the nitrided layer the amounts of titanium and nitrogen atoms are almost equal. This proves that in the upper zone titanium nitride (TiN) is present. This phase as well as Ti2N was identified by the X-ray diffraction method. We can conclude that the
structure of this layer can be identified as TiN+Ti2N+aTi(N). By analysing the amount of elements present on the surface of the oxynitrided layer, we can draw the conclusion that titanium dioxide is the phase which forms in this kind of process. The small amount of nitrogen indicates that titanium oxynitride is also present. X-ray diffraction shows that these phases are present in the layer together with Ti2N under the upper zone.
44
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
Table 1 The surface chemical composition of the layers obtained during 12 h of treatment Element
Nitrided layer (at%)
Oxynitrided layer (at%)
Carbonitrided layer (at%)
Titanium Oxygen Nitrogen Carbon Aluminium
54 traces 45 traces 1
29 56 14 traces 1
22 traces 37 40 1
This layer can be described as TiO2+Ti(ON)+Ti2N+aTi(N). When the carbonitriding takes place TiCN is formed on the surface with overstoichiometric amounts of nitrogen and carbon. The TiC and TiN phases crystallize in the NaCltype crystallographic structure and are soluble in each other. X-ray diffraction analysis also proved the presence of titanium carbonitride together with the Ti2N phase. These layers can be described as TiCN+Ti2N+aTi(N). Fig. 3 shows the curves of the corrosion resistance of the nitrided, oxynitrided and carbonitrided layers. The layers obtained in plasma carbonitriding and oxynitriding processes have high corrosion resistance compared to the titanium alloy itself. The nitriding process leads to the formation of a surface TiN layer which offers a better corrosion resistance than the substrate without treatment. The wear resistance of the layers produced during 3 h of treatment is presented in Fig. 4. We can see that, after the plasma treatments, the wear resistance of the substrate increased considerably. The specimens of untreated titanium alloy underwent seizure after 10 min. The highest frictional wear resistance is shown by the nitrided layers. The plasma oxynitriding produces a layer which has the lowest wear resistance among all the three treatments. This layer also underwent seizure but not so quickly as a titanium alloy (without a surface layer), when a large unit pressure was applied. Similar results for layers produced after 6 and 12 h of treatment were obtained. The greater thickness of the diffusion layers prevented the seizure of the oxynitrided layers. We can assume that the increased oxygen content in the surface zone not only decreases the hardness of the layer, but also the wear resistance.
Fig. 3. Corrosion resistance of the surface layers measured in the 0.5 M NaCl solution.
Fig. 4. Linear wear of the surface layers produced on titanium alloy by different plasma treatments as a function of time measured under unit loads of 200 and 400 MPa. Linear wear of the titanium alloy is given for comparison.
Fig. 5 shows the Wohler fatigue strength curves determined for the starting Ti–1Al–1Mn alloy subjected to annealing at 8001C for 3 h, to glow discharge assisted nitriding, oxynitriding and carbonitriding for 3 h. The figure clearly shows
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
Fig. 5. Plots of the Wohler fatigue strength obtained for the starting material (Ti–1Al–1Mn alloy) subjected to annealing at 8001C for 3 h, to glow discharge assisted nitriding, oxynitriding and carbonitriding for 3 h.
that all the treatments increase the fatigue strength of the alloy, the increase due to the nitriding process being greater than that achieved after the oxynitriding process. However, the use of plasma carbonitriding produces a layer with the greatest fatigue strength. This fatigue strength depends on the thickness of the layer, which increases with the process time. In the annealed titanium alloy, the limiting value of the fatigue strength increased from 350 to 390 MPa after the 12 h nitriding, to 410 MPa for 12 h carbonitriding and only to 380 MPa after the 12 h oxynitriding process. Fig. 6 illustrates this relationship. In the present study, we have found that an increased carbon content in the layer increases not only surface hardness, but also its fatigue strength.
45
Fig. 6. Plots of the Wohler fatigue strength obtained for the Ti– 1Al–1Mn subjected to glow discharge assisted nitriding, oxynitriding and carbonitriding for 3 and 12 h.
layer produced when air is introduced additionally into the gaseous atmosphere, are less advantageous than those of the TiN+Ti2N+Ti(N) nitrided layer: the hardness, limiting value of the fatigue strength and corrosion and frictional wear resistance are lower. This is so since titanium dioxide TiO2Fa hard but brittle phaseFformed in the near-surface zone of the layer, reduces the fatigue strength, wear and corrosion resistance. The incorporation of carbon in the layer produces a titanium carbonitride TiCN in the near-surface zone which has the greatest hardness, good corrosion and wear resistance and causes the greatest increase in the fatigue strength.
References 4. Conclusion The glow discharge assisted nitriding, oxynitriding and carbonitriding processes applied to titanium and its alloys widen the application range of these materials. These treatments produce surface layers of a diffusion character, which have a high hardness, high frictional wear and corrosion resistances and an increased fatigue limit. It should be noted that the properties of the oxynitrided
[1] Bylica A, Sieniawski J. Titanium and its alloys. Warsaw: Polish Scientific Publishing House, 1985. [2] Budinsky KE. Wear 1991;151:203–17. [3] Bell T, Bergman HW, Lanagan J, Morton PH. Surf Eng 1986;2:133. [4] Tokaji K, Ogawa T, Shibata H. Fatigue 1994;16:331. [5] Shibata H, Tokaji K, Ogawa T, Hori C. Fatigue 1994;16:370. [6] Fleszar A, Wierzcho!n T, Sun KK, Sobiecki JR. Surf Coat Technol 2000;131:62. [7] Renevier N, Collignon P, Michel H, Czerwiec T. Surf Coat Technol 1999;111:128.
46
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
[8] Rolin! ski E, Sharp G, Cowgill DF, Peterman DJ. J Nucl Mater 1998;252:200. [9] Thomann AL, Sicard E, Boulmer-Leborgne C, Vivien C, Hermann J, Andreazza-Vignole C, Andreazza P, Meneau C. Surf Coat Technol 1997;97:448. [10] Fu Y, Batchelor AW. Wear 1998;214:83. [11] Mordike BL, Bregman HW. Mater Res Soc Symp Proc 1986;58:335.
[12] Sarkissian AH, Bourque-Viens A, Paynter RW, SaintJacques G, Stansfield BL. Surf Coat Technol 1998;98:1336. [13] Tang BY, Chu PK, Wang SY, Chow KW, Wang XF. Surf Coat Technol 1998;103–104:248. [14] Burakowski T, Wierzchon! T. Surface engineering of metalsFprinciples, equipment, technologies. New York, Washington, Boca Raton, FL: CRC Press, 1999. [15] Polish Standard PN-83/H-04302, 1983.
The influence of glow discharge nitriding, oxynitriding and carbonitriding on surface modification of Ti–1Al–1Mn titanium alloy J.R. Sobiecki*, T. Wierzchon! , J. Rudnicki Faculty of Materials Science and Engineering, Warsaw University of Technology, 02-507 Warsaw, Wołoska 141, Poland Received 7 March 2001; accepted 8 May 2001
Abstract Recent surface treatment studies show that titanium alloys should have an improved resistance to frictional wear and fatigue strength limit without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface nitrided, oxynitrided and carbonitrided diffusion layers. This paper presents the results of metallographic examinations, corrosion and wear resistance tests, surface chemical composition investigation, as well as rotating and bending fatigue tests. These surface treatments increase the useful properties of the titanium alloy. The influence of treatment time and the thickness of the layers on its properties are also investigated. r 2001 Elsevier Science Ltd. All rights reserved. Keywords: Plasma nitriding; Oxynitriding; Carbonitriding; Titanium alloy; Wear and corrosion resistance; Chemical composition; Fatigue strength
1. Introduction Titanium and its alloys have many attractive properties including high specific strength and modulus, excellent corrosion resistance, and, in some cases, excellent cryogenic properties [1]. They are widely used in aerospace applications and many corrosive environments. However, titanium alloys have found little use in general engineering application, mainly because of their poor tribological properties, such as poor abrasive and adhesive wear resistance, a tendency to galling and seizure, a tendency to fretting wear and *Corresponding author. Fax: +48-33-660-8514. E-mail address: [email protected] (J.R. Sobiecki).
fretting fatigue, and high coefficients of friction [2]. In order to improve such surface properties a variety of surface engineering techniques, such as gas nitriding [3–5], plasma nitriding [6–8], laser nitriding [3,9–11], and ion implantation [12,13] have been successfully applied. However, it has also been found that such treatments lead to a decrease of fatigue strength in titanium alloys [3,11]. As the reasons for the reduction in fatigue strength have not been made clear, it is necessary to study systematically the fatigue behaviour of surface-treated materials in pure titanium and titanium alloys. Among the methods with most potential are glow discharge assisted techniques, which permit control of the layer formation process as regards both the structure and the
0042-207X/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 2 - 2 0 7 X ( 0 1 ) 0 0 3 7 3 - 6
42
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
phase composition and, thus modify the properties of the layers. The present paper describes a modification of the plasma discharge nitriding treatment of titanium a alloy, i.e. glow discharge assisted oxynitriding and carbonitriding introducing oxygen or carbon into the surface zone to form a TiON or TiCN layer.
2. Experimental methods The specimens were made of titanium alpha alloy (1–2.5%Al, 0.7–2.0%Mn Ti in balance). The process was carried out in a universal apparatus for different types of thermo-chemical treatment under glow discharge conditions [14]. The DC power supply was used. During the process, the voltage was 800 V and the current was 5 A. The samples were subjected to plasma nitriding at a temperature of 8001C in a nitrogen atmosphere, plasma oxynitriding at the same temperature in nitrogen and air (the volume percentage of air content was 2%) and plasma carbonitriding also at 8001C in nitrogen and methane atmosphere (the volume percentage of methane was 15%). The pressure in the reactor chamber was about 4 hPa. The time of the treatment was 3, 6 and 12 h. The metallographic examination was made using a Neophot microscope on previously etched samples in a solution of chemical composition: 96 cm3 H2O+2 cm3 HNO3+2 cm3 HF. The microhardness of the layer was measured by a Hanneman unit connected with the same microscope, and the load was 50 g. The corrosion resistance was measured in a 0.5 M NaCl solution by the potentiodynamic method using the Atlas–Sollich computerized equipment designed for electrochemical examinations. The polarization curves were determined by polarizing the samples from a potential of 1000 mV towards anodic potentials, at a potential varying rate of 50 mV/min. Prior to the measurements, the samples were kept in the test solution for 24 h. The potential was measured with respect to a calomel electrode (SCE). The frictional wear resistance was measured using the ‘‘three rollers+taper method’’ [15]. In this test, friction is applied under specified conditions, between three fixed cylindrical specimens (rollers)
8 mm in diameter, covered with surface layers, and a rotating conical counter-specimen (taper). The linear wear expressed as the wear depth was determined by measuring the diameters of ellipses formed on the surfaces of each roller. The results were then averaged. The counter specimen was made of SW7M high speed steel quenched and tempered to a hardness of 64 HRC. Constant unit loads of 200 and 400 MPa were applied. The phase composition of the layers was determined using a Philips PW 1830 X-ray diffractometer using a CoKa source. The chemical composition of the layers was analysed using the EDS unit fitted to the LEO 1530 microscope. The fatigue behaviour was examined in a fatigue testing machine (bending rotation) at a constant bending moment and a rotational speed of 2200 rotations per minute. The fatigue strength was determined in 24 samples. The samples were loaded using the step method with the stress variation increment s=0.5 kg/mm2 (ca. 5 MPa). The results were compared with those obtained for the Ti–1Al–1Mn alloy annealed at a temperature of 8001C for 3 h.
3. Results Fig. 1 shows the microstructures of the surface layers formed on the Ti–1Al–1Mn titanium alloy obtained after different thermo-chemical treatments. The time of treatment was 3 h. Microstructures obtained following the 12 h of treatment are presented in Fig. 2. The layers produced during 3 h of treatment are about 15 mm thick. The plasma oxynitriding produced the layers which had the highest thickness (about 25 mm). Increasing the time to 12 h also increases the thickness of the layer to 25 mm for the nitriding and carbonitriding processes and to 35 mm for oxynitrided layers. The increased thickness of the oxynitrided layers can be explained by the higher speed of diffusion of oxygen into the titanium substrate. The surface microhardness of the layers are independent of the time of the process. They range from 1850 HV0.05 for the oxynitrided layers to 2100 HV0.05 for the nitrided layers and 2240 HV0.05 for the carbonitrided layers.
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
43
Fig. 1. Microstructures of the surface layers formed on titanium alloy during (a) nitriding, (b) oxynitriding and (c) carbonitriding after 3 h of treatment.
Fig. 2. Microstructures of the surface layers formed on titanium alloy during (a) nitriding, (b) oxynitriding and (c) carbonitriding after 12 h of treatment.
The surface chemical compositions of the layers obtained during 12 h processes are summarized in Table 1. As one can see from Table 1, in the nitrided layer the amounts of titanium and nitrogen atoms are almost equal. This proves that in the upper zone titanium nitride (TiN) is present. This phase as well as Ti2N was identified by the X-ray diffraction method. We can conclude that the
structure of this layer can be identified as TiN+Ti2N+aTi(N). By analysing the amount of elements present on the surface of the oxynitrided layer, we can draw the conclusion that titanium dioxide is the phase which forms in this kind of process. The small amount of nitrogen indicates that titanium oxynitride is also present. X-ray diffraction shows that these phases are present in the layer together with Ti2N under the upper zone.
44
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
Table 1 The surface chemical composition of the layers obtained during 12 h of treatment Element
Nitrided layer (at%)
Oxynitrided layer (at%)
Carbonitrided layer (at%)
Titanium Oxygen Nitrogen Carbon Aluminium
54 traces 45 traces 1
29 56 14 traces 1
22 traces 37 40 1
This layer can be described as TiO2+Ti(ON)+Ti2N+aTi(N). When the carbonitriding takes place TiCN is formed on the surface with overstoichiometric amounts of nitrogen and carbon. The TiC and TiN phases crystallize in the NaCltype crystallographic structure and are soluble in each other. X-ray diffraction analysis also proved the presence of titanium carbonitride together with the Ti2N phase. These layers can be described as TiCN+Ti2N+aTi(N). Fig. 3 shows the curves of the corrosion resistance of the nitrided, oxynitrided and carbonitrided layers. The layers obtained in plasma carbonitriding and oxynitriding processes have high corrosion resistance compared to the titanium alloy itself. The nitriding process leads to the formation of a surface TiN layer which offers a better corrosion resistance than the substrate without treatment. The wear resistance of the layers produced during 3 h of treatment is presented in Fig. 4. We can see that, after the plasma treatments, the wear resistance of the substrate increased considerably. The specimens of untreated titanium alloy underwent seizure after 10 min. The highest frictional wear resistance is shown by the nitrided layers. The plasma oxynitriding produces a layer which has the lowest wear resistance among all the three treatments. This layer also underwent seizure but not so quickly as a titanium alloy (without a surface layer), when a large unit pressure was applied. Similar results for layers produced after 6 and 12 h of treatment were obtained. The greater thickness of the diffusion layers prevented the seizure of the oxynitrided layers. We can assume that the increased oxygen content in the surface zone not only decreases the hardness of the layer, but also the wear resistance.
Fig. 3. Corrosion resistance of the surface layers measured in the 0.5 M NaCl solution.
Fig. 4. Linear wear of the surface layers produced on titanium alloy by different plasma treatments as a function of time measured under unit loads of 200 and 400 MPa. Linear wear of the titanium alloy is given for comparison.
Fig. 5 shows the Wohler fatigue strength curves determined for the starting Ti–1Al–1Mn alloy subjected to annealing at 8001C for 3 h, to glow discharge assisted nitriding, oxynitriding and carbonitriding for 3 h. The figure clearly shows
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
Fig. 5. Plots of the Wohler fatigue strength obtained for the starting material (Ti–1Al–1Mn alloy) subjected to annealing at 8001C for 3 h, to glow discharge assisted nitriding, oxynitriding and carbonitriding for 3 h.
that all the treatments increase the fatigue strength of the alloy, the increase due to the nitriding process being greater than that achieved after the oxynitriding process. However, the use of plasma carbonitriding produces a layer with the greatest fatigue strength. This fatigue strength depends on the thickness of the layer, which increases with the process time. In the annealed titanium alloy, the limiting value of the fatigue strength increased from 350 to 390 MPa after the 12 h nitriding, to 410 MPa for 12 h carbonitriding and only to 380 MPa after the 12 h oxynitriding process. Fig. 6 illustrates this relationship. In the present study, we have found that an increased carbon content in the layer increases not only surface hardness, but also its fatigue strength.
45
Fig. 6. Plots of the Wohler fatigue strength obtained for the Ti– 1Al–1Mn subjected to glow discharge assisted nitriding, oxynitriding and carbonitriding for 3 and 12 h.
layer produced when air is introduced additionally into the gaseous atmosphere, are less advantageous than those of the TiN+Ti2N+Ti(N) nitrided layer: the hardness, limiting value of the fatigue strength and corrosion and frictional wear resistance are lower. This is so since titanium dioxide TiO2Fa hard but brittle phaseFformed in the near-surface zone of the layer, reduces the fatigue strength, wear and corrosion resistance. The incorporation of carbon in the layer produces a titanium carbonitride TiCN in the near-surface zone which has the greatest hardness, good corrosion and wear resistance and causes the greatest increase in the fatigue strength.
References 4. Conclusion The glow discharge assisted nitriding, oxynitriding and carbonitriding processes applied to titanium and its alloys widen the application range of these materials. These treatments produce surface layers of a diffusion character, which have a high hardness, high frictional wear and corrosion resistances and an increased fatigue limit. It should be noted that the properties of the oxynitrided
[1] Bylica A, Sieniawski J. Titanium and its alloys. Warsaw: Polish Scientific Publishing House, 1985. [2] Budinsky KE. Wear 1991;151:203–17. [3] Bell T, Bergman HW, Lanagan J, Morton PH. Surf Eng 1986;2:133. [4] Tokaji K, Ogawa T, Shibata H. Fatigue 1994;16:331. [5] Shibata H, Tokaji K, Ogawa T, Hori C. Fatigue 1994;16:370. [6] Fleszar A, Wierzcho!n T, Sun KK, Sobiecki JR. Surf Coat Technol 2000;131:62. [7] Renevier N, Collignon P, Michel H, Czerwiec T. Surf Coat Technol 1999;111:128.
46
J.R. Sobiecki et al. / Vacuum 64 (2002) 41–46
[8] Rolin! ski E, Sharp G, Cowgill DF, Peterman DJ. J Nucl Mater 1998;252:200. [9] Thomann AL, Sicard E, Boulmer-Leborgne C, Vivien C, Hermann J, Andreazza-Vignole C, Andreazza P, Meneau C. Surf Coat Technol 1997;97:448. [10] Fu Y, Batchelor AW. Wear 1998;214:83. [11] Mordike BL, Bregman HW. Mater Res Soc Symp Proc 1986;58:335.
[12] Sarkissian AH, Bourque-Viens A, Paynter RW, SaintJacques G, Stansfield BL. Surf Coat Technol 1998;98:1336. [13] Tang BY, Chu PK, Wang SY, Chow KW, Wang XF. Surf Coat Technol 1998;103–104:248. [14] Burakowski T, Wierzchon! T. Surface engineering of metalsFprinciples, equipment, technologies. New York, Washington, Boca Raton, FL: CRC Press, 1999. [15] Polish Standard PN-83/H-04302, 1983.