Felületmódosítás

1. Felületmódosítás Korszerű anyagok és technológiák, MSc 2015

2. A felületi tulajdonságok tudománya: átfogó (interdiszciplináris) terület • A felület a tiszta fizikai és kémiai tulajdonságok szemszögéből. • Topográfiával kapcsolatos tulajdonságok (felületi érdesség). • Tágabb értelemben: „surface engineering”: komplex nézőpont • Kapcsolat a felületi tulajdonságok, az alkalmazás és az alkalmazott technológiák között. • (Tiszta fizikai és kémiai tulajdonságok: alapkutatás szemszöge.) • A felületek tulajdonsága a felhasználók szempontjából: „surface engineering”.

3. Kondenzált anyagok nagy fajlagos felülettel:a „komplexitás” alapja a felület • Felületi tulajdonságok kialakulása ← klaszterek tulajdonsága(mérethatás): • „Méretfüggő” tulajdonságok: átmenet az önálló atomtulajdonságok és a termodinamikailag stabil makroszkópos tulajdonságok között; A redukált ionizációs energia különböző szabadfelületű fémklaszterek esetében a klaszterátmérő reciprokának függvényében

6. Aim: the local modification of surface properties changing either the local composition or the structure orboth of them. The desired surface properties are often contradict to those in the bulk! (i.e. local hardness, local corrosion resistance) examples: development of peculiar compositional relations on the surface of semiconductors The development of hard, wear- or corrosion-resistant surfaces on cutting, drilling tools Development of optical or decorative layers Two alternatives: Covering the surface with protective layer (corrosion resistant layers) Structural or compositional changes in the surface layer

7. Inductor Inductor Cog wheel Cog wheel Traditional methods Increase of non-metallic element concentration in the surface layer, using heterogeneous reaction. i.e. iron/steel heating in appropriate gas-mixture (carbonization, decarbonization, nitridation) CH4 [C]Fe + 2H2 CH4/H2 2NH3  [N]Fe + 3H2 NH3/H2 Layer deposition using electrochemical or chemical methods Hard chromium-layer (3-500 μm, HV 900-1100) Ni-P amorphous layer (3-30 μm, HV 1300) Surface hardening using inductive heating and subsequent rapid cooling

9. forrás: Szurdán Szabolcs

11. x Példa: Al-Si bevonat „press hardening” technológiához ausztenitesítés: 880-950°C - ~ 10 % Si

12. Deposition of thin layers by physical methods (Physical Vapour Deposition, PVD) • favour: • High melting point metals can be deposited to low substrat temperature because • T substrat can be low • The electrical conductivity of substrate not necessary • Complex multilayers can be deposited • Alloy deposition is also possible • „clean technology” (without the formation of products causing environmental pollution) • limits: • Expensive (vacuum circumstances)

13. PVD (physical vapor deposition) The original, traditional technologies: chemical reactions are not included ( i.e. mirror production) Heating Substrate Source Vacuum system Chamber Cover plate Substrateholder Mask Layer thickness measure Window Valve Evaporate source Freezer Diffusion pump Pre-vacuum pumps Source Schematic illustration of the principle The technical arrangement Crucial in every deposition is the layer duration, which is influenced mainly by the surface preparation (cleaning)

14. Physical Vapour Deposition Source: Platit

16. The real structure of the deposited layer versus the substrat to melting point temperature Deposition of TiN layer on the surface of tools for the purpose of surface hardenening

17. The dimensions Source: Platit

18. Some another exmples Source: Platit

19. Machined length [m] Machined length [m] Cutting speed [m/min] Feed [mm/rev] The machined length versus the main machining parameters: cutting speed (a) and feed (b) ( •TiN coated, o TiN coated and newly grinded, □nitride coating ■ without coating

20. Chemical Vapour Deposition, (CVD) basic principles In the original form, the procedure consist of two isothermal reactions: a.) at T1 temperature M +nXMXn (M layer forming metal , X halogen) At T1 a volatile compound is formed b.) at T2 (T2 > T1 ) MXnM + nX Thermal decomposition of MXnoccur on the substrate surface Subsequently the decomposition process, the halogen molecule is circuated (in order to form new volatile molecules) Typical chemical reactions in the CVD procedure: Metal-halogenides are often used as precursor materials in these techniques. The reason: volatile compounds (high tension even at low temperatures!) (see tables) Besides the metal-layer depositions, the method also used for compound depositions(refractory carbides, silicides, borides)

21. Typical CVD reactions Typical reactants, processing parameters for a few depositions

22. Typical reactants, processing parameters for a few depositions

23. The important metals and ceramics produced by the CVD method

24. Examples for the compound-layer deposition • The TiN layer deposition: • 2 TiCl4 +4 H2 +N2 2 TiN +8HCl • Al2O3 layer deposition: • 2AlCl3 +3CO2 +H2  Al2O3 +3CO +6HCl

25. Halide preparatory Outgoing gas cleaner and neutralizer Gases Gas mixer Vacuum pump Programming unit Heating bell Heating bell Deposition chambers Heating controller Gas supply The scheme of complete unit for CVD technology

26. The properties of deposits produced by CVD , layer-substrate: the compatibility

27. Favour: -high temperature:deposit accomodat even the complicated, irregular surfaces (inner surfaces can be covered)

28. Another example Tantállal bevont gégecső

29. The limits: • The high substrat temperature (for example for structural or carbon steels is not recommended! 6-800 oC!) • Expensive reactants

30. Polymer DLC Graphite Diamond Gyémánt és gyémántszerű amorf rétegek DLC: Diamond-Like Carbon The properties of CVD-produced policrystalline diamond layers: high chemical resistance, high hardness, high wear resistance, low frictional resistance

31. Hardness and young moduli of carbon- based coated layers Me: fém az elektromos vezetőképesség növeléséhez, fém-karbidok H: hidrogéntartalom a C2H2 elbomlásából a: amorf fázis tartalmú réteg Si: szilíciumtartalom i-C: mátrix sp3-as kötésekkel, de amorf

32. The techniques of plasma spraying Plazmagáz energiatartalma Helium Hővezetési tényező

33. Shematic drawing of plasma spraying and the SEM photograph of the sprayed coating

34. Characteristics of plasma-sprayed layers Improvement of Succesfully applied for • Abrasive properties • Hardness • Corrosion resistance • (Especially in those cases, when the base material is low-cost • improvement of bio-compatibility (implanted parts) • the surface improvement of carbon-steels • surface hardness increase • corrosion resistance increase

35. The modes of plasma welding: inner, outher wire supply, powder supply

36. The laser surface treatments

37. Excimer laser Nd::YaG laser Diode laser CO2 laser Iron Absorption degree [%] Wavelength (mm) The effectivity highly depends on the absorption degree Excimer laser The absorption degree of various laser beams as a function of wavelengths

38. Milled surface Grinded surface Polished surface Material: CMo4 Hardened layer thicjness [mm] Feed [mm/min] The absorption degree also depends on the surface roughness The thickness of hardened layer as a function scanning rate on steels with various surface roughness

39. Laser marking on steel surfaces

40. The local structural change as the basis of code formation Depending on the applied energy density various structural changes can be induced (phase transformation, recrystallisation etc)