Surface Engineering of Metals - Principles, Equipment and Technologies Part 10 pps

Table 4.6 Effect of implantation on microhardness and tribological properties of PB102 * phosphor bronze (From Saritas, S., et al. [106]. With permission from Elsevier Science.) Fig. 4.30 Effect of sliding distance in pin-on-disk rubbing pair on coefficient of friction of stainless steel, not implanted and implanted by C + + Ti + and N + ions. A low coefficient of friction is exhibited by steel implanted with tin or molybdenum, and subsequently by sulfur (Table 4.7). Implantation with nitrogen of TiN coatings increases their wear resistance [109], and it has a similar effect on TiB coatings [110]. Alloying with molybdenum or cobalt of coatings implanted by nitrogen causes improvement of lubricity [4]. The depth to which the properties of the implanted material are modi- fied, which may be likened to the thickness of the implanted layer, is not great. In an extreme case it reaches 1 µm. On steels it usually does not exceed 0.2 to 0.3 µm. However, despite a really thin initial thickness, it practically averages values greater by a factor one to two orders of magnitude during the process of abrasive wear, due to Implanted ions Ion energy[keV] Ion dose [ions/cm 2 ] Micro- hardness HV Implantation depth [m] Initial coefficient of friction Wear after 500 m sliding distance (under 10 N load) [10 -4 cm 3 ] No implantation 178–10 0.01(oxide) 0.12 16.5 B + 40 5 10 17 284–10 0.012 0.35 11.0 C + 20 1 10 17 183–7 0.18 16.8 N + 20 1 10 17 207–4 0.15 15.5 40 1 10 17 not measured - 15.5 40 5 10 17 218–6 0.015 0.16 13.0 P + 40 5 10 17 269–10 0.9 0.30 11.6 Coefficient of friction © 1999 by CRC Press LLC Fig. 4.32 Migration of nitrogen into 440B steel during abrasive wear test. (From Wolf, G.K., [70]. With permission.) Fig. 4.33 Initial implantation profile (a) and its migration (b) during abrasive wear test of WC-Co (tungsten carbide - 8% Co) alloy and Ti-6Al-4V titanium alloy, implanted by nitrogen ions of 40 keV energy and dose of 1·10 17 N + /cm 2 . (From Fayeulle, S. [71]. With permission from Elsevier Science.) migration during the friction process while on the surface, the hard layer is reproduced [14]. Nitrogen atoms are displaced into the material to a distance 10 to 150 times that of the depth of implantation. The effect of im- plantation ceases only after attaining a depth of 12 to 30 µm [4]. The effect of nitrogen migration, later also termed auto- or quasi-im- plantation of nitrogen, was observed for the first time in 1978 by G. Dearnaley and N.E.W. Hartley. They concluded that at a depth 100 times greater than the initial depth of implantation, after the friction process there © 1999 by CRC Press LLC still remained approx. 40% of the implanted ions. Other researchers have confirmed that the effect of forced migration of nitrogen dominates in abra- sive wear of ferritic steels [40, 70, 71]. Fig. 4.32 shows such migration of nitrogen into steel grade 440B, while Fig. 4.33 shows the shift in the implan- tation profile in WC-Co and TA6V alloys. 4.6.2 Strength properties of implanted materials Ion implantation, especially of nitrogen ions, but also of C, Ba, Mn, Ni, Ti, Ta, W, Re (Table 4.8), causes a rise of fatigue strength [102, 111-113]. This is attributed to the presence of radiation defects and the formation of significant compressive stresses, caused by a fine dispersion of hard phase precipita- tions [38], hardening of structure, blocking of dislocation movement which usually occurs after implantation and, finally, a certain “smoothing” of the surface. In the macro scale, ion implantation may be looked upon as a lightly smoothing treatment. Table 4.8 Implanted ions improving fatigue properties The positive effect of implantation on low cycle fatigue strength is connected mainly with the formation of radiation defects increasing ho- mogeneity of deformations (decreasing slip planes) and decreasing struc- ture defects upon formation of new phases [1]. High cycle fatigue strength is more affected by residual stresses form- ing in the implanted layer. Compressive stresses increase the value of fatigue limit while tensile stresses lower it [1, 114]. Implantation causes a rise in fatigue strength by several tens percent (Fig. 4.34). Titanium alloys, alloyed by nitrogen, carbon and barium, cause a rise of fatigue strength by 10 to 20%. It should be added that nitrogen and carbon, besides saturating the solid solution, form finely dispersed nitrides and car- bides which strengthen the structure of the implanted layer. Barium effec- tively impedes the migration of oxygen to the surface layer. The combination of implantation with earlier thermo-chemical treatment or by glass beading usually also causes an increase of the fatigue limit [119]. For example, in grade 30HGSNA * steel the fatigue limit, which prior to implanta- tion is approximately 500 MPa, rises to approximately 760 MPa after glass beading and after subsequent nitrogen ion implantation at 100 keV Implanted material Ions Ti alloys N; C; Ba High alloy steels N; Mn; C; B; Ni Low alloy steels N; Ti © 1999 by CRC Press LLC nitrogen by a dose of 2·10 17 ions/cm 2 yielded an insignificant increase of the fatigue limit value, while after natural or artificial aging the fatigue limit of samples subjected to rotational bending rose by a factor of 10. Fig. 4.36 Effect of xenon ion dose of 600 keV energy on brittle fracture of graphite: 1 - not implanted graphite; 2 - implanted graphite. (From Hirvonen, I.P., et al. [118]. With permission from Elsevier Science.) Resistance to brittle cracking of ceramics and sintered carbides is en- hanced by the implantation of Zr, Cr and Ti. 4.6.3 Hardness and adhesion of implanted materials Ion implantation of the majority of metallic, ceramic and synthetic mate- rials by N, P, Co, Y, Cr, Ti, Mo, Zr, Nb and Ta causes an increase of hardness of the implanted metallic layer (Table 4.9) and of the coating deposited on the substrate prior to or during the implantation process [119, 120, 121]. Implantation causes a rise of microhardness, due to the formation of strong compressive stresses and hard microinclusions of nitrides, carbides Fig. 4.37 Variations of microhardness vs. ion dose: a) steel implanted by nitrogen ions of different energy levels: 1 - E51100 steel, implanted with ions of 60 keV energy; 2 - 100W1 * steel, implanted by ions of 50 keV energy; b) TiN coating, deposited on stain- less steel by magnetron sputtering, implanted by ions of 500 keV energy. (Curve 1 - from Kolitsh, A., and Richter, E. [121], curve 2 - from Hochmuth, K., et al. [18], Fig. b - from Padmanabhan, K.R., et al. [54]. With permission.) © 1999 by CRC Press LLC and borides in a manner which depends on the type of ions and on their dose (Fig. 4.37), as well as on the temperature of the implanted material (Fig. 4.38). Fig. 4.38 Effect of steel temperature on microhardness of C100W1 * steel, implanted by carbon ions of different doses: 1 - dose of 1·10 17 C + /cm 2 ; 2 - 3·10 17 C + /cm 2 ; 3 - 6·10 17 N + /cm 2 ; 4 -1·10 17 C + /cm 2 ; 5 - 3·10 17 N + /cm 2 . (From Hochmuth, K., et al. [18]. With permission.) Fig. 4.39 Dependence of forces of adhesion of TiN coating, deposited on glass by means of magnetron sputtering and implanted by krypton ions of 500 keV energy: a) on ion dose at different substrate temperatures; b) on substrate temperature for ion dose of 5·10 15 Kr + /cm 2 . (From Padmanabhan, K.R., et al. [54]. With permission.) Fig. 4.40 Changes in resistivity of Ni layer, deposited on glass by magnetron sputter- ing, vs. dose of implanted krypton ions of 500 keV energy. (From Padmanabhan, K.R., et al. [54]. With permission.) © 1999 by CRC Press LLC Fig. 4.41 Corrosion current vs. time of exposure in a bath of 0.9% NaCl (pH=7) for an implanted and not implanted Ti-6Al-4V surgical alloy; the value of 5µA·h corresponds to a material loss of 1 nm. (From Wolf, G.K. [48]. With permission.) also of Ar, He, Xe, Cu, Ni, Mo. The majority of investigations carried out to date was devoted to the effect of implantation on atmospheric corro- sion. Other topics of research were corrosion in acids [70], in body fluids (Fig. 4.41) [57, 123, 124] and in water [125]. Ion implantation leads to the improvement of corrosion resistance of metallic materials in oxidizing atmospheres through [38]: – formation in the surface layer of compounds with new physico-chemi- cal properties, e.g., corrosion resistance of titanium implanted by palladium rises more than 1000 times in comparison with not implanted material [126, 127]; – formation - with appropriate selection of ions and their dose - of amorphous properties which also feature enhanced corrosion resistance, similarly to amorphous materials obtained by splat cooling [128]. Amor- phous properties may be obtained by implantation of pure metals, e.g., cop- per by ions of tantalum or tungsten and of iron by titanium. Amorphous structures formed by implantation also feature high stability, e.g., copper implanted by tungsten does not lose its amorphous properties at 600ºC in 1.5 h [127]; – blockage of channels of easy oxygen diffusion (in the case of implant- ing of atoms greater than those of the lattice, e.g., of barium, strontium, cal- cium, rubidium or cesium into titanium) [38]; – formation of compact oxide layers, like Al 2 O 3 (by e.g., implantation of Al ions into copper) or Cr 2 O 3 , SnO 2 , SiO 2 , and YCrO 3 (by e.g., implantation of yttrium into chromium-bearing steel) and CaTiO 2 , which constitute a barrier for oxidation processes [129]; © 1999 by CRC Press LLC – plastization of brittle oxide layers which prevents the formation of microcracks exposing the implanted surface, modification of defect distribu- tion and conductivity by oxides; – implantation of ions which act catalytically, e.g., of platinum and ions of metals belonging to the same group, which slow down oxygen migra- tion; – implantation of ions which slow down cathodic processes, e.g., Pb; – modification of electrical conductivity of oxides [38]. In practice, ion implantation is sporadically applied to improve corro- sion resistance of metals. 4.6.5 Other properties of implanted materials Catalytic properties of metallic materials and ceramics are improved by the implantation of Pt, Mo and Pd ions. Hydrogen embrittlement in steels is diminished by the implantation of Pt and Pd ions. Nitride formation in steels and aluminum is facilitated by the implan- tation of Ti and Mo ions. Optical properties of glasses and of synthetic materials is modified by the implantation of Nb, Ti, Mo, Zr and Y ions. 4.7 Application of implantation technology In surface engineering of metals, the method applied on an industrial scale is mainly primary ion beam implantation with recoil ion beam implan- tation trailing behind [130]. Currently the beginnings of a rapid advance of industrial application of ion mixing, as well as of research in the field of applications for plasma ion implantation are observed [42]. Of the techniques of primary ion beam implantation, implantation of nitrogen ions has been predominant in industry worldwide [43, 95, 130], especially applied to cutting and forming tools, less often to machine com- ponents. This technique is responsible for a rise of tool life by 2 to 10 times (Tables 4.11 and 4.12). The life increase obtained depends not only on the type of implanted material and implanting ions, but also, to a great extent, on the mating material of the rubbing pair or of the object treated by the implanted tool [6, 22, 55, 59, 84, 88, 131-134]. Nitrogen ion implantation has a lot in common in the utilitarian sense with gas and/or plasma nitriding, which both also significantly increase the service life of machine parts and tools. Fig. 4.42 shows volumetric wear of stainless steel, nitrided and ion implanted. It can be seen that right until the moment of complete wear of the nitrogen ion implanted layer, the material exhibits a better behavior than the nitrided one [81]. Interesting effects may also be obtained by the implantation by nitrogen ions of prior nitrided layers. © 1999 by CRC Press LLC Table 4.13 Steels used for tooling and their properties after implantation (From Iwaki, M., et al. [133]. With permission from Elsevier Science.) Type of steel AISI grade Chemical composition [%] Heat treat- ment Knoop hardness (under 2N load) Changes CSiMnNiCrMoV Co other hardness wear anodic current 12345678910 11 12 13 14 15 16 Tool steels H13 0.32-0.42 ≤1.5 ≤1.5 ≤0.25 4.5-5.5 1.0-1.5 0.4 - 0.18S PH 430-460 P21 0.15 0.3 1.5 3.0 0.8 0.3 - - 1.0Cu, 1.0Al PH 17-4PH 0.07 - - 4.5 17.0 - - - 3.0Cu, 0.3Nb PH Alloy steels D2 1.5 - - - 12.0 1.0 0.4 - QT 630-690A2 1.0 0.2 0.6 - 5.3 1.1 0.2 - QT H13 0.35-0.42 0.8-1.2 0.3-0.5 - 4.8-5.5 1.2-1.6 0.5-1.1 - 0.13S QT M1 ≤0.03 ≤0.1 ≤0.1 17.0-19.0 - 4.5 - 7.0 8.5 0.3-0.5 Ti0.05-0.15Al SA 520-700M3 ≤0.03 ≤0.1 ≤0.1 17.0-19.0 - 4.5-5.5 - 3.5-9.5 1.2-1.8 Ti0.05-0.15Al SA M4 ≤0.03 ≤0.1 ≤0.1 17.0-19.0 - 3.5-4.5 - 12.0-13.0 1.2-1.8 Ti0.05-0.15Al SA Stainless steels 420 0.38 13.6 - QT 580-600 420 13.6 QT Notation: PH - prehardening, QT - quench and temper, SA - solution annealing and aging - at 2.5•10 17 NO + /cm 2 ; - at 2•10 17 N + /cm 2 © 1999 by CRC Press LLC constitutes the only possibility of obtaining uniformity within a broad range of alloys, in the solid solution, of systems which feature limited solubility in the solid and liquid state [1, 128, 136, 137]. Table 4.14 Possibilities of application of ion mixing Table 4.15 Possibilities of application of dynamic mixing In perspective, one can visualize a combination of implantation with diffusion, made possible by additional heating of the load [25]. 4.8 Advantages and disadvantages of ion implan- tation techniques Advantages of ion implantation are the following: – The already mentioned potential possibility of implantation by any cho- sen element of any material in a short time (of the order of 10 to 100 s/cm 2 of surface) and at any temperature (but not exceeding 600ºC), although very Application Substrate material Elements in mixture, magnetron sputtered, ion plated Ion beam Wear resistance Ti-6Al-4V alloy Sn N + Oxidation resistance Superalloys, steels Y Ar + Surface catalysis Carbon Pt Ar + Corrosion resistance Steel titanium iron CrPd; PtAl; Cr Ar + ; Kr + Ar + Ar + ; Xe + Resistance to surface tarnishing Copper Al; Cr Ne + Improvement of adhesion Al2O3, quartz, ceramic, plastics Al; Cu; Au He + ; Ne + Application Substrate material Vapour deposited elements Ion beam Obtaining of superhard regular boron nitride Steel B N + Strongly adherent hard layers (TiN, HfN) Steel Ti; Hf N + Strongly adherent metallic layers of high density and small porosity Any material Al; Cu; Au Ne + Anti-corrosion coatings Steels Cr; Ta Ne + ; He + Preparation of substrate for PVD coatings Any material Ti N + © 1999 by CRC Press LLC limited in practical applications; furthermore, the possibility of introducing combinations of alloying additives. – Possibility of obtaining concentrations of alloying additives which exceed their solubility in the alloyed material (usually approximately 20%, up to over 50% maximum). – Ease of electrical process control, as well as possibility of precise control of concentration and distribution of alloying additives by pro- gramming the dose and energy of ions, with the possibility of monitoring. – Possibility of conducting the process at low temperatures (usually below 200ºC), allowing its application independently of classical heat treat- ment of finished components, without changes of shape and dimensions. This technique allows the retention of tool tolerances down to several nm without the need for subsequent finishing operations [39]. – Independence of technique of the effect of adhesion. – Low electrical energy consumption. – Cleanliness of process (vacuum) and non-pollution of the environ- ment. – Material economy. Among the disadvantages are - The inherent beam characteristic of the process (it is possible to im- plant only surfaces in the line of beam operation; best results are obtained on surfaces which are perpendicular to the ion beam axis). This does not apply to plasma ion implantation. - Small depth of implantation (maximum up to 1 µm) in the case of beam implantation and greater in the case of plasma ion implantation, which increases, however, during service. - Impossibility of implantation of loads with complex geometrical shapes and walls of deep holes (this does not apply to plasma ion implantation). - Very high cost of ion beam implanters, of the order of $150,000 to 200,000 U.S. As an example, the price of a the big “Tecvac 221” implanter is £200,000 (pound sterling). - High operating costs of implantation, from $0.03 to $0.10 per cm 2 [19] to $0.4 to $0.65 per cm 2 [105] of implanted surface. - Necessity of very thorough cleaning of load surface prior to implan- tation. - Differences between technological possibilities of implantation. As an example, it is relatively easy to implant metallic materials with nitrogen, boron, carbon, aluminum, tin, cerium or silicon but difficult to implant with titanium, palladium, yttrium and very difficult with platinum. - Requirement of very highly trained and qualified personnel to oper- ate implanters. - Necessity to use radiological shields, protecting the operator from X-ray radiation which occurs during the operation of ion beam implanters. - Only small automation of the implantation process: to this day single chamber implanters are being built. It is possible, however, to build a three-chamber implanter (Fig. 4.43), in a manner similar to vacuum cham- © 1999 by CRC Press LLC [...]... Journal of Metals, No 35, 1983, pp 1 7-2 2 81 Cohen, A., and Rosen, A.: The influence of nitriding process on the dry wear resistance of 1 5-5 PH stainless steel Wear, Vol 108 , No 2, 1986, pp 10 7-1 58 82 Dillich, S.A., and Singer, I.L.: Effect of Ti implantation on the friction and surface chemistry of Co-Cr-W alloy Thin Solid Films, 108 , 1983, pp 21 9-2 27 83 Erck, R.A., Fenske, G.R., Erdemir, A., and Nichols... 1986, 3, pp 10 1-1 05 49 Kaut, R.A., and Sartwell, B.D.: Ion beam enhancement of vapour deposited coatings Journal of Vacuum Science and Technology, A, 1985, Vol 3, No 6, pp 267 5-2 676 50 Barnavon, Th., Jaffrezic, H., Marest, G., Moncoffre, N., Tousset, J., and Fayeulle, S.: Influence of temperature of nitrogen implanted steel and iron Materials Science and Engineering, No 69, 1985, pp 53 1-5 37 51 Dearnaley,... friction and wear behaviour of a phosphor bronze Wear, Vol 82, No 2, 1982, pp 23 3-2 55 107 Ohmae, N.: Recent work on tribology of ion plated thin films Journal Vacuum Science and Technology, 1976, Vol 4, pp 8 2-8 7 108 Sioshansi, P., and Au, J.J.: Improvement of sliding wear for bearing grade steel implanted with Ti and C Materials Science and Engineering, No 69, 1985, pp 16 1-1 66 109 Wanka, K., Kimura, T., and. .. ion beam implanted vapour deposition and the resulting improvement of the wear resistance Tetsuo-Hagane, 1988, Vol 74, No 11, pp 21772184 110 Yust, C.S., McHargue, C., and Harris, L.A.: Friction and wear of ion-implanted TiB2 Materials Science and Engineering, Dec 1988, T.A 105 /106 , pp 48 9-4 96 111 £abêdŸ J.: The effect of ion implantation on the fatigue life of self-aligning ball bearings Proc.: 5th... system and connected with the movement of masses, charges and atoms, © 1999 by CRC Press LLC as well as their interaction) and their product pV; V - volume; p - pressure; σ - surface tension; s - surface; µ - chemical potential; n - number of moles; ϕ - electrical potential; q - electrical charge The system remains in equilibrium when the sum of the components of the equation (5.1) is constant In the... 1985, pp 22 7-2 31 © 1999 by CRC Press LLC 104 Zhai, C.F., De, L.L and Zhong, Z.X.: Modification of tribological characteristics of metals of N implantation Nuclear Instruments and Methods, 209, 10, 1983, pp 88 1-8 87 105 Richter, E.: Verschleissshutz durch Ionenimplantation Schmierungstechnik, No 11, 1985, pp 32 4-3 26 106 Saritas, S., Procter, R.P.M., Ashworth, V., and Grant, W.A.: The effect of ion implantation... Polish) Proc.: Conference on Technology of Superficial Layer Formation on Metals, Rzeszów (Poland), 9-1 0 June 1988, pp 10 6-1 13 25 Burakowski, T.: Trends in development of heat treating (in Polish) Section for Fundamentals of Technology of the Machine-Building Committee of the Polish Academy of Sciences, Institute of Precision Mechanics, Warsaw, March 1988, pp 7 8-8 4 © 1999 by CRC Press LLC 26 Piekoszewski,... implantation Thin Solid Films, No 109 , 1983, pp 3 7-4 5 96 Singer, I.L., and Jeffries, R.A.: Effects of implantation energy and carbon concentration on the friction and wear of Ti-implanted steel Appl Phys Lett., No 43, 1983, pp 92 5-9 27 97 Singer, I.L., and Jeffries, R.A.: Surface chemistry and friction behaviour of Tiimplanted 5 2100 steel Vacuum Science Technology, A, Vol 1, No 2, Part 1, AprJune 1983, p 317... pp 1 3-1 5 117 Hohmuth, K., Richter, E., Rauschenbach, B., and Blochowitz, C.: Fatigue and wear of metalloid-ion-implanted metals Materials Science and Engineering, No 69, 1985, pp 19 1-2 01 118 Hirvonen, I.P., Stone, D., Nastasi, M., and Hannula, S.P.: Hardening of graphite surface by ion beam amorphisation Scripta Metallurgica, Vol 20, No 5, May 1986, pp 64 9-6 52 119 Follstaedt, D.M., Knapp, J.A., and. .. during the service of the object, e.g as a result of loading, wear, chemical action of the environment The structure of the superficial layer, constituting a “set of elements of the real surface of the object and structure of its superficial layer, such as geometrical elements of the surface and physical properties of the material, e.g., grain size,” evidently also depends on the type of treatment Researchers . 0.4 - QT 63 0-6 90A2 1.0 0.2 0.6 - 5.3 1.1 0.2 - QT H13 0.3 5-0 .42 0. 8-1 .2 0. 3-0 .5 - 4. 8-5 .5 1. 2-1 .6 0. 5-1 .1 - 0.13S QT M1 ≤0.03 ≤0.1 ≤0.1 17. 0-1 9.0 - 4.5 - 7.0 8.5 0. 3-0 .5 Ti0.0 5-0 .15Al SA 52 0-7 00M3. 16 Tool steels H13 0.3 2-0 .42 ≤1.5 ≤1.5 ≤0.25 4. 5-5 .5 1. 0-1 .5 0.4 - 0.18S PH 43 0-4 60 P21 0.15 0.3 1.5 3.0 0.8 0.3 - - 1.0Cu, 1.0Al PH 1 7-4 PH 0.07 - - 4.5 17.0 - - - 3.0Cu, 0.3Nb PH Alloy steels D2 1.5 - - - 12.0. ≤0.1 ≤0.1 17. 0-1 9.0 - 4. 5-5 .5 - 3. 5-9 .5 1. 2-1 .8 Ti0.0 5-0 .15Al SA M4 ≤0.03 ≤0.1 ≤0.1 17. 0-1 9.0 - 3. 5-4 .5 - 12. 0-1 3.0 1. 2-1 .8 Ti0.0 5-0 .15Al SA Stainless steels 420 0.38 13.6 - QT 58 0-6 00 420 13.6