Właściwości mikromechaniczne i tribologiczne stopów tytanu po azotowaniu i tlenoazotowaniu jarzeniowym

• Autorzy: Kot M. , Moskalewicz T. , Zimowski S. , Czyrska-Ftlemonowicz A. , Rakowski W.

Warianty tytułu

EN

Micromechanical and tribological properties of titanium alloys after glow discharge nitriding and oxynitriding

• Języki publikacji: PL

Abstrakty

PL

W artykule przedstawiono wyniki badań mikrostruktury i właściwości mikromechanicznych oraz tribologicznych warstw wytworzonych metodą azotowania i tlenoazotowania jarzeniowego na stopach tytanu Ti-6Al-4V oraz Timetal 834. Szczegółowe badania mikrostruktury przeprowadzone za pomocą TEM umożliwiły określenie składu fazowego oraz grubości poszczególnych stref warstwy wierzchniej. Wyznaczono gradient twardości i odporność na zarysowanie warstw oraz ich odporność na zużycie. Twardość warstwy azotowanej na stopie Timetal 834 wynosi ponad 2100 HV, a warstw tlenoazotowanych ok. 900 HV. Azotowanie jarzeniowe zwiększa odporność stopu Timetal 834 na zużycie przez tarcie ponad 130 razy. Odporność na zużycie stopu Ti-6Al-4V po tlenoazotowaniu jest taka sama, jak po azotowaniu. Dla stopu Timetal 834 jest prawie dwukrotnie niższa dla tlenoazotowania niż azotowania.

EN

Titanium alloys are nowadays frequently used because of their high strength, low density and maximum working temperature up to 600° C (Timetal 834) and find many applications especially in aerospace, marine industry and as biomaterials eg. for endoprotesis. But they have found little use in mechanical engineering. The main problem for titanium alloys is their poor tribological properties, low hardness, low resistance to wear and tendency to galling. Titanium alloys are subjected to various surface treatments giving hard external layers to improve mechanical properties, reduce coefficient of friction and wear. Titanium alloys: two-phase Ti-6A1-4V and pseudo-alfa Timetal 834 after nitriding and oxynitriding under glow discharge have been tested. The microstructural analyses were performed using light microscopy (LM) and analytical transmission electron microscopy (TEM). Nitrided layer on Ti-6A1-4V alloy has thickness 130-200 žm. For timetal 834 nitrided layer is thinner 70-180 žm. TEM investigations of cross-sectional thin foils revealed graded character with sublayers: outermost delta-TiN followed by delta'-Ti2N, epsilon-Ti2N and nitrogen-rich alfa(N) solid solution. Oxynitrided layers are thinner - 10 žm and 40 žm for Ti-6A1-4V and Timetal 834 respectively. These layers have also graded character with TiO, epsilon-Ti2N nitrogen-rich alfa(N) solid solution sublayers. Microhardness, Young modulus, resistance to scratch and tribological properties have been measured for all layers. A Micro-Combi-Tester of CSEM Instruments was used to measure hardness and Young Modulus and scratch resistance. Microindentations have been done on cross-sectional samples using Vickers indenter and 50 mN load. Rockwell C indenter, 200 mm tip radius has been used for scratch tests. Wear tests were performed on the ball-on-disc equipment under 2N load, track radius r = 5 mm, linear speed v = 0,03 m/s. AI2O3 balls - 1 mm diameter have been used. Wear rate was calculated from wear profiles after 1800 cycles. Hardness of nitrided layers is higher than oxynitrided for both alloys. Delta-TiN sublayer on Timetal 834 after nitriding has hardness 2100HV0,005. Outermost sublayers TiO produced by oxynitrification have hardness 900HV0,005. Graded character of all tested layers lead to gradient of hardness, which is gradually lower and lower for next sublayers. All tested layers show very good adhesion. For nitrided layers neither fracture nor delamination have been observed for load up to 20 and 25 N for Ti-6A1-4V and Timetal 834 respectively. Small area spallation, shell shaped cracks and delaminations occurred above these loads. Cohesive cracks have been observed above 20 N and 24 N for oxynitriding layers on Ti-6A1-4V and Timetal 834. Nitrided layer on Timetal 834 has highest wear resistance (Ws = 6,7 [L. mm3/(N*m)]*10-6). For Ti-6Al-4V wear is two times higher and is similar to wear of both oxynitriding layers. Nitrification and oxynitrification improve wear resistance. Wear is 60-130 times smaller than for untreated alloys. Results of all performed tests show than nitrification and oxynitrification under glow discharge is a prospective method for titanium alloys treatment to obtain light elements with high strength and wear resistance.

Słowa kluczowe

PL

warstwy powierzchniowe; stopy tytanu; mikrostruktura; twardość; odporność na zużycie przez tarcie

EN

surface layers; titanium alloys; microstructure; hardness; wear resistance

• Wydawca: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
• Czasopismo: Tribologia
• Rocznik: 2007
• Tom: nr 2
• Strony: 261--271
• Opis fizyczny: Bibliogr. 15 poz., rys., tab.

Twórcy

autor

Kot M.

autor

Moskalewicz T.

autor

Zimowski S.

autor

Czyrska-Ftlemonowicz A.

autor

Rakowski W.

• Akademia Górniczo-Hutnicza, Wydział Inżynierii Mechanicznej i Robotyki, 30-059 Kraków, al. Mickiewicza 30,

Bibliografia

• 1. Boyer R.R.: An overview on the use of titanium in the aerospace industry. Materials Science and Engineering A, 213 (1996) 103-114.
• 2. Gorynin I.V.: Titanium alloys for marine application. Materials Science and Engineering A, 263 (1999) 112-116.
• 3. Wang K.: The use of titanium for medical apllication in USA. Materials Science and Engineering A, 213 (1996) 134-137.
• 4. Gunawarman B., Niinomi M., Akahori T., Souma T., Ikeda M., Toda H.: Mechanical properties and microstructures of low cost alfa titanium alloys for healthcare applications. Materials Science and Engineering C, 25 (2005) 304-311.
• 5. Long M., Rack H.J.: Friction and surface behaviour of selected titanium alloys during reciprocating-sliding motion. Wear, 249 (2001) 158-168.
• 6. Avelar-Batista J.C., Spain E., Housden J., Matthews A., Fuentes G.G.: Plasma nitriding of Ti6A14V alloy and AISIM2 steel substrates using D.C. glow discharges under a triode configuration. Surface and Coatings Technology, 200 (2005)1954-1961.
• 7. Zhecheva A., Sha W., Malinov S., Long A.: Enhancing the microstructure and properties of titanium alloys through nitriding and other surface engineering methods. Surface and Coatings Technology, 200 (2005) 2192-2207.
• 8. Sobiecki J.R., Wierzchoń T., Rudnicki J.: The influence of glow discharge nitriding, oxynitriding and carbonitriding on surface modification of Ti-lAl-lMn titanium alloy. Wear, 64 (2002) 41-46.
• 9. Wierzchoń T.: Surface engineering of titanium alloys: New prospective applications. Materials Science Forum, 426-432 (2003) 2563-2568.
• 10. Czyrska-Filemonowicz A., Buffat P.A., Łucki M., Moskalewicz T., Rakowski W., Lekki J., Wierzchoń T.: Transmission electron microscopy and atomic force microscopy characterisation of titanium-base alloys nitrided under glow-discharge. Acta Materialia, 53 (2005) 4367-4377.
• 11. Moskalewicz T., Zimowski S., Kitano Y., Wierzchoń T., Czyrska-Filemonowicz A.: Microstructure and properties of the oxynitrided Ti-6Al-4V alloy, Kovove Materialy-Metallic Materials, 44 (2006) 133-138.
• 12. Moskalewicz T., Czyrska-Filemonowicz A.: Microstructure and properties of surface treated Timetal 834. International Journal of Materials Research, 97 (2006) 1059-106.
• 13. Kot M., Rakowski W.: Wpływ podłoża i chropowatości powierzchni na pomiar twardości cienkich warstw. Zagadnienia Eksploatacji Maszyn, 40 (2005) 17-30.
• 14. Langier M.T.: An energy approach to the adhesion of coatings using the scratch test. Thin Solid Films, 117 (1984) 243-249.
• 15. Bull S.J., Berasategui E.G.: An overview of the potential quantitative coating adhesion measurement by scratch testing. Tribology International, 39 (2006) 99-114.