Surface Engineering of Metals - Principles, Equipment and Technologies Part 15 ppsx

Burakowski, T., and Senatorski, J.: Comparison of resistance to tribological wear of carbur-ized and nitrided layers in Polish, Trybologia, No.. Piaskowski, Z.: The effect of surface de

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6 8 Morel, S., and Cuba≈a, J.: Catalysing burn effect of rest CO and reduction emission NOx

by ceramic coatings Proc.: Research Problems in Heating Energy, Warsaw, 8-10 December,

1993, p 235-242.

69 Sulima, A.M., Sulov, V.A., and Yagodnitski, Yu.D.: Superficial layer and service properties of

machine components (in Russian) Publ Masinostroenye, Moscow 1988.

70 Kocañda, S., and Szala, J.: Fundamentals of fatigue calculations (in Polish) PWN, Warsaw,

1985.

7 1 Katarzyñski, S., Kocañda, S., and Zakrzewski, M.: Research of mechanical properties of

metals (in Polish) Edition III, WNT, Warsaw 1967.

72 Dyl˙g, Z., and Or≈oœ, Z.: Fatigue strength of materials (in Polish) WNT, Warsaw, 1961.

73 Joint Report: Metal fatigue (translation from English) WNT, Warsaw 1962.

74 ISO R 373-1964 General principles for fatigue testing.

7 5 Przybylski, W.: Burnishing technology WNT, Warsaw 1987.

76 Nakonieczny, A., and Szyrle, W.: Fatigue strength, residual stresses and microstructure of

carburized and shot-peened layer (in Polish) Proc.: II Polish Conference Surface Treatment,

13-15 October, 1993, Kule/Czestochowa, pp 61-66.

7 7 Gurnej, T.R.: Fatigue of welded structures (translation from English) WNT, Warsaw 1973.

78 Olszañski, W., Su≈kowski, I., Tacikowski, J., and Zyœk, J.: Thermo-chemical treatment (Heat

treatment of metals) (in Polish) Vol 5, ODOK SIMP - IMP, Warsaw 1979.

7 9 DIN 50323 Tribologie Begriffe Deutsches Institut für Normung 1990.

80 Senatorski, J.: Evaluation of materials for sliding friction nodes (in Polish) Dissertation

Insti-tute of Precision Mechanics, Warsaw 1994.

81 Jastrzêbski, Z.D.: The nature and properties of engineering materials John Wiley and Sons, New

York 1976.

82 Krzemiñski-Freda, H.: Ball-bearings (in Polish) PWN, Warsaw 1989.

83 £uszczak, A., Machel, M., and Wachal, A.: Tribology Friction and lubrication of machine

com-ponents (in Polish) Vol I and II Military Technical Academy, Warsaw 1979.

84 I¿ycki, B., Maliszewski, J., Piwowar, S., and Wierzchoñ, T.: Diffusion brazing (in Polish).

WNT, Warsaw 1974.

85 Garkunov, D.N.: Selective transportation in heavily loaded friction nodes (in Russian) Publ.

Masinostroenye, Moscow 1982.

86 Simons, E.N.: Metal wear: a brief outline Frederick Muller Limited, London 1972.

87 Bowden, F.P., and Tabor, D.: Introduction to tribology (translation from English) WNT,

War-saw 1980.

88 Wranglen, G.: Fundamentals of corrosion and metal protection (in Polish) WNT, Warsaw 1985.

89 Burakowski, T., and Senatorski, J.: Comparison of resistance to tribological wear of

carbur-ized and nitrided layers (in Polish), Trybologia, No 3, 1984, pp 4-8

90 Burakowski, T., Senatorski, J., and Tacikowski, J.: Effect of microstructure of diffusion

lay-ers on their tribological properties (in Polish) Trybologia, No 6, 1986, pp 4-8

91 Senatorski, J., and Tacikowski, J.: Tribological properties of diffusion layers on structural

and tool steels Trybologia, No 2, 1988, pp 11-13.

92 Senatorski, J.: Problems related to increasing of tribological properties of parts by heat treatment (in

Russian) Series: Scientific-technological progress in machine-building, Edition 28 tions of International Center for Scientific and Technical Information - A.A Blagonravov Institute for Machine Building Research of the Academy of Sience of USSR, Moscow 1991.

Publica-93 Rogalski, Z., and Senatorski, J.: Über den Einfluss der thermochemischen

Ober-flächenbehandlung auf die Fressbeständigkeit von Konstruktionsstählen IfL-Mitteilungen,

1967, pp 11-16.

94 Kostetski, B.I., Barmosenko, A.I., and Slaviskaya, L.V.: The role of crystalline structure and

orientation of monocrystals in the formation of the internal wear process (in Russian).

Metallofizika, No 40, 1972, pp 24-30.

95 Piaskowski, Z.: The effect of surface deformation on the wear resistance of the superficial

layer (in Polish) Trybologia, No 6, 1987, pp 13-15.

96 Janowski, S., Senatorski, J., and Szyrle, W.: Initial research of the effect of residual stresses

on wear resistance (in Polish) Science Periodicals of Rzeszów Technical University, No 82, Mechanika, vol 28, 1991, pp 127-132.

97 Marczak, R.: Progress in investigations of the Garkunov effect (in Polish) Proc.: Problems of

wear-free friction in machines, Radom, 12-13 May, 1993, pp 126-137.

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98 Krol, M.: The application of metal polymers for improvement of efficiency and reliability of

combustion engines (in Polish) Proc.: Problems of wear-free friction in machines, Radom, 12-13

May, 1993, pp 196-204.

99 Garkunov, D.N.: Introductory presentation Proc.: Problems of wear-free friction in machines,

Radom, 12-13 May, 1993, pp 6-11.

100 Firkowski, A.: The mechanism of selective transportation effect and its usable aspect (in

Polish) Proc.: XVI Fall School of Tribology, Pi≈a-Tuczno 1988, pp 96-102.

101 Marczak, R.: The effect of wear-free friction (in Polish) Paper presented at the meeing of the

Committee for Machine Building of the Polish Academy of Sciences, in Borków (Poland), 3-4 October, 1991.

102 Korzyñski, M.: The application of burnishing to improve tribological properties of machine

components (in Polish) Science Publications of Rzeszów Technical University, No 36, Mechanika, vol 15, 1987, pp 131-133.

103 Willis, E.: Surface finish in relation to cylinder liners Wear, No.109, 1986, pp 351-366.

104 Prowans, S.: Physical metallurgy (in Polish) PWN, Warsaw 1988.

105 Przyby≈owicz, K.: Physical metallurgy (in Polish) Edition II WNT, Warsaw 1992.

106 Uhlig, H.: Corrosion and protection against it (translation from English) WNT, Warsaw 1976.

107 Tomashov, D.N.: Theory of corrosion and metal protection (Polish translation from Russian).

110 Tacikowski, J., and Zyœk, J.: Modern methods of gas nitriding Proc.: Monotheme

Confer-ence on Nitriding and Related Processes, Rzeszów, 26 June 1980, pp 24-42.

111 Surface treatment for improved performance and properties Edited by J.J Burke, V.Weiss Plenum

Press, New York - London 1982.

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Fig 5.22 Thickness of nitrided layer on surfaces A and B of a titanium sample, vs time

of nitriding; process temperature T = 900ºC, p = 3 hPa (From Roliñski, E., [20] With

permission.)

Surface A (external) was subjected to bombardment by ions and tral particles formed in the plasma during glow discharge, while on sur-face B only adsorption processes took place because glow discharge doesnot penetrate such a narrow gap Obtained were nitrided layers of thesame phase composition and thickness on both surfaces A and B [20].Fig 5.22 shows thicknesses of the nitrided layer on surfaces A and B of thetitanium samples vs time of nitriding The significant role of chemisorp-tion is also illustrated by investigations concerning the formation of tita-nium nitride layers in a chamber with the so-called hot anode, whichyielded surface layers both on the cathode, as well as on the anode attemperatures of the order of 550ϒC [46]

neu-On transition metals, chemisorption of most gases, e.g., of nitrogen ontitanium, is a non-activated process In the case of the nitrogen-iron system,however, a relatively small activation energy of approximately 80 kJ/mole

is needed [3, 20] In the presence of atomic nitrogen, however, under glowdischarge conditions, chemisorption proceeds freely without the need foractivation energy Chemisorbed particles may be deformed at the surfaceand dissociation chemisorption may take place [38], with the formation offree atoms and radicals For these reasons, chemisorbed particles are chemi-cally more active [4] During chemisorption, when additional energy ap-pears, a chemical reaction may proceed As an example, in the process offormation of titanium carbide layers, the adsorbed lower titanium chlorides(TiCl2 and TiCl3) may react with carbon from the steel matrix, in accordancewith the reactions:

TiCl2(g) + 2H + C(s) ♦ TiC(s) + 2HCl(g) ∆G°1000 K = -373 kJ/mole (5.4)TiCl3(g) + 3H + C(s) ♦ TiC(s) + 3HCl(g) ∆G°1000 K = -450 kJ/mole (5.5)where: ∆Gϒ1000 K - molar free enthalpy of the reaction under standard pres-sure at a temperature of 1000 K

Recapitulating, the effect of chemisorption plays a basic role in glowdischarge treatments because, intensified to a large extent by ion sputter-

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ing, it affects the process in which the following separate stages, in modynamic equilibrium, can be distinguished These are

ther-1) chemical reactions in the gas phase, constituting a condition of ply of active particles of elements forming the superficial layer,

sup-2) chemisorption of these particles at the treated surface,

3) processes of diffusion and the associated phase transformations (e.g.,glow discharge nitriding and boriding) or chemical reactions at the loadsurface (PACVD methods, Fig 5.23)

Fig 5.23 Changes in free enthalpy (∆GϒT) of a chemical reactions determining the formation of a titanium carbide layer under glow discharge conditions.

It follows then that the formation of the superficial layer may be enced primarily by the direction of chemical reactions in the gas atmo-

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sphere This depends on the chemical composition and flow rate of the gasmixture, as well as electrical parameters It is also influenced by the appro-priate preparation of new load surface from the point of view of chemisorp-tion, which has a direct effect on diffusion processes and on the course ofchancel reactions which are the essential condition of formation of superfi-cial layers in PACVD methods.

5.3 Glow discharge furnaces

Units for carrying out thermo-chemical treatment of the time described in

preceding sections is called the glow discharge furnace and are utilized

for such diffusion processes as e.g., nitriding, carbonitriding or boriding, aswell as for PACVD methods They are composed of: a working chamber, avoltage generator, a system for metering reactive gases, a vacuum systemand a control-measurement system They may differ by the shape of theworking chamber, by the power of the voltage generator, design of currentfeed-throughs, method of load fixturing, and by the method of metering

of reactive gases, in particular of chlorides and metal-organic compounds

In the case of furnaces used for PACVD methods, such furnaces may fer by the design of the working chamber and by the method of elimina-tion of harmful components of the gas atmosphere exiting the workingchamber, such as vapors of BCl3, HCl, TiCl2, TiCl3, etc

dif-In all types of glow discharge furnaces, dynamic vacuum is used Thisallows the establishment of a dynamic equilibrium between the basic stages

of the process, i.e chemical reactions in the gas atmosphere, with the aid

of technological parameters such as temperature, partial pressure andchemical composition of the gas mixture The chemical reactions are es-sential to guarantee a supply of active particles forming the layer throughchemisorption, diffusion and the resultant phase transformations or chemi-cal reactions of adsorbed active particles The appropriate selection of thegas mixture and treatment conditions creates a possibility of process con-trol, in particular of microstructure and phase composition of the layerbeing formed, i.e of its properties

Fig 5.24 Schematic of equipment used for glow discharge nitriding; 1 furnace; 2

-direct current supply; 3 - load; 4 - system for metering the mixture of reactive gases; 5

- vacuum system.

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Fig 5.25 Schematic of equipment for carrying out glow discharge processes in chloride-vased atmospheres, containing vapors of

metal-organic compounds: 1 - work chamber; 2 - cathode; 3 - internal screens; 4 - direct current supply; 5 - refrigerating system; 6, 7, 20 - vacuum valves; 8 - “mechanical” filter; 9 - vacuum pump; 10 - water seal; 11¸14 - metering and cut-off valves; 15 - reservoir, e.g with boron chloride

or Ti(OC3H7)4; 16 - thermostat; 17, 19 - gas purifiers, 18 - gas cylinders; 21 - temperature measuring device; 22 - flow meters.

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In glow discharge diffusion processes, especially in those accomplished

by PACVD methods, two types of working chambers are used:

- cold wall (cooled anode - chamber wall) in which the load (cathode)

is heated by glow discharge;

- hot wall, i.e., with auxiliary heating of the chamber (retort) walls which

allows more favorable conditions of gas flow and the utilization of loadpolarization other than cathodic, as well as conduction of thermo-chemicaltreatments under reduced pressure (LPCVD methods) [33, 47, 48]

Diagrams of glow discharge furnaces for nitriding and its tions, e.g., sulfo-nitriding, oxy-nitriding, oxy-carbonitriding and boriding, aswell as diagrams of versatile furnaces for diffusion treatments and PACVDand LPCVD processes are shown in Figs 5.24 to 5.27

modifica-Fig 5.26 Schematic of a versatile unit for glow discharge diffusion processes by the PACVD

and LPCVD methods: 1 - work chamber; 2 - internal screens; 3 - resistance heated retort furnace; 4 - system for temperature stabilization and measurement; 5 - gas metering system; 6 - metering unit for the layer forming element, e.g TiCl4, Ti(OC3H7)4; 7 - vacuum system; 8 - pressure gauge; 9 - voltage supply; 10 - current feed-through; 11 - load.

Fig 5.27 Schematic of a stand for glow discharge nitriding with a JONIMP-500/900

bell-type furnace [48]: 1 - glow discharge furnace; 2 - vacuum pump system; 3 - nace hearth; 4 - load; 5 - supply and control cabinets (From Trojanowski, J., [48] With

fur-permission.)

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Fig 5.28 Schematic of the JON-PEG furnace for glow discharge nitriding: 1 - resistance

furnace; 2 - electrical supply unit for resistance furnace; 3 - work chamber (vacuum retort); 4 - lid; 5 - vacuum system; 6 - load; 7 - thyristor direct current supply unit; 8 - reactive atmosphere metering system (From Trojanowski, J., [48] With permission.)

For nitriding and its modifications these are furnaces used on a wideindustrial scale They are of the pit or bell type with dimensions depen-dent on the size of the load Working chambers in pit-type furnaces aredesignated for slender and log parts which are usually nitrided in thesuspended position, e.g., crankshafts, injection mold screws, cylinders Onaccount of their big heights (up to 6 m) they are installed in pits Modulardesign makes possible their extension as the need arises Chambers withbigger usable diameters are designed as bell type and in this case, the load isplaced on a base Often they are designed with double base and an exchange-able working chamber which allows a more effective utilization of the fur-nace (Fig 5.28) Such a furnace is used for glow discharge nitriding of bigand heavy parts placed in an upright position, e.g., dies [48]

A glow discharge furnace for thermo-chemical treatment of complexshaped loads has been designed and built at the Institute of PrecisionMechanics in Warsaw, Poland (see Fig 5.28) [48] The selection of power

of the direct current power generator depends on the surface area of thetreated load For example, in the nitriding process, power supply units arerated at up to 150 kW

In thermo-chemical treatment with electric activation pulsed currentpower supply may also be used, where changes of voltage (frequency)constitute a new parameter, independent of discharge power and of otherprocess parameters, e.g., substrate temperature, treatment time, pressure andcomposition of gas mixture [49-51] Schematics of furnaces powered

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