Diffusion Carbide Layers, Formed on the Surface of Steel in the Vacuum Titanizing Process

TRANSACTIONS OF MATERIALS AND HEAT TREATMENTVol.25 No.5PROCEEDINGS OF THE 14TH IFHTSE CONGRESSOctober 2004Diffusion Carbide Layers, Formed on the Surface of Steel in the VacuumTitanizing ProcessKASPRZYCKA Ewa, SENATORSKI Jan, NAKONIECZNY Aleksander, BABUL TomaszInstitute of Precision Mechanics, Warsaw, PolandAbstract: Diffusion layers produced on carbon steel surface in vacuum titanizing process were investigated. Studies oflayers thickness, their morphology, titanium, carbon and iron concentration depth profiles in the diffusion zone of titanizedlayers were carried out. The effect of process parameters such as time and temperature on the kinetics of layer growth onsteel surface was investigated. Tribocorrosion resistance of titanized layers was determined.Key words: Diffusion layers, thermochemical treatment, vacuum titanizing, wearlcorrosion resistanceDIFFUSION TITANIZING is applied to increase theIhe resulting layers were investigated by X-raydurability of tools, which operate under wearstructural analysis using Philips diffractometer and byconditions [1]. There is considerable bibliographicalspectral line analysis with SU-30 CAMECA X-raydata concerming the diffusion titanizing process, itmicroanalyser.particular, problems connected with hard titaniumMetallographic examinations andthicknesscarbide layers are quite well elaborated [2-4].measurements of titanized layers were carried out withIn this paper, a novel vacuum titanizing process,an optical microscope. I ayer microstructure waswhich involves treating steel in titanium vapor at therevealed by nital etching. Microhardness of titanizedtemperature over 1000°C under low pressure, has beenlayers was measured by Vickers method.proposed [5]. A porous material containing titaniumTo determine the tribological properties an Amslerwas employed as the source of titanium vapor. Inmachine of A135 type was used.contrast to other titanizing methods (powder, gas, etc.),"he friction unit was disk and plate [9]. Testingneither toxic reagents i.e. chlorides nor a hydrogenparameters were as follows: speed of disk sample (n), .containing atmosphere have been used [6].200 rpm; average sliding friction speed (v), 0.42 m/s;Carbon content plays an important role in theload of frictional system by concentrated contact (P),diffusion titanizing of steels, since its difusion to the25 daN; total friction time (), 2 h. Lubrication withsurface (up hill diffusion) during the process leads to its50% water solution of physiological salt with drip feedcombination with titanium to form carbides. At highof 60 drops/min. Microscopic measurement of linearcarbon content in steels, the obtained diffusion layerswear with accuracy of 5 μm was used to estimateare composed of titanium carbides. Such layers aretribocorrosion damagehard and wear resistant [7-8].The objective of this paper is to determine the2. Resultsmicrostructure，growth kinetics and tribocorrosionX-ray surface structure analysis of titanized surfacesproperties of carbide layers produced on carbon steelon the 45 steel revealed a substantial presence ofsurface during vacuum titanizing process.titanium carbide (TiC) and trace Fe2Ti intermetallic1. Experimentalphase.A metallographic cross-section of carbide layer hasA structural 45 steel (non - alloyed steel of gradeshown that the layer was unetched, as opposed to theequivalent to AISI 1045: 0,45% C) has been selectedsteel base. A decarburized zone was present in the steelfor experiments.base just bellow the layer.Titanizing of this steel was carried out in a coldConcentration depth profiles of Ti, C and Fe in thewall vacuum fumace at the temperature range oflayer diffusion zone are typical of a carbide titanized1000+1100°C with pressure in the range of 10 Pa tolayer (Fig. 1). Concentration of titanium in the carbide10~2 Pa using the novel method [5]. Crucibles of highlayer is about 79 wt. % and of carbon about 19 wt. %.temperature-resistant steel were used to contain theKinetics of layer growth on the 45 steel surface wassteel samples in contact with porous materialstudied by performing a series of titanizing processescontaining titanium. After the crucibles were placed infor va中国煤化工8 and 10 h at thethe vacuum furmace, the pumping system was startedtempet1100°C.and, then, heating was activated. After the process wasff ICNMHGknes for variousterminated, the batch was cooled with the furnace.temperatures is illustrated on Fig. 2. A parabolicVol.25 No.5TRANSACTIONS OF MATERIALS AND HEAT TREATMENT647dependence of layer thickness on the time suggests that250titanizing process is controlled by the diffusion in steel.10Ti200gE80o✧✧写150黄蛋40LayerCoregoo_o501520!2Depth [μm]Fig. 1. Depth profles of Cr, Fe and C concentration of carbide0,51,5layer produced on the 45 steel surface.Friction time [h]Fig.3. Run of linear wear of toughened (1) and diffusiontitanized 45 steel (2) subjected to the tribocorrosiondamage% 10The results obtained show very high wear resistancef titanized steel in conditions of sliding friction by2concentrated contact in the presence of corrosionmedium.3. ConclusionsOn the base of obtained results it is possible toformulate the following conclusions:48(1) Application of the vacuum titanizing enablesProcess time [h]a formation of titanium carbide layers on the surfaceof 45 steel, with microhardness about 2400 HV.Titanium concentration in the layer was 79 wt. %.Fig. 2.Thickness of titanized layers produced on theCarbon concentration in this layer was about 19 wt. %.45 steel surface versus process time forThe carbide layer thickness reached about 15 um in 10temperatures: 1- 1025%C, 2- 1050°C,3- 1075*C,hours at temperature 1100C.4 -1100C.(2) Titanized carbide layers growth on steel surfaceThickness of carbide layers produced on the 45 steelis controlled by the diffusion in steel.(3) Diffusion layers obtained in the vacuumsurface during vacuum titanizing process reached about15 μm in 10 hours at temperature of 1100°C. Layertitanizing process are characterized by hightribocorrosion resistance.microhardness was about 2400 HV.Results of wear resistance of the titanized layersubjected to the tribocorrosion damage are presented inAcknowledgementFig. 3, which shows linear wear as a function of frictionThis中国煤化工2Committee Scientifictime. For comparison, the tribological characteristicRe19)obtained for toughened 45 steel is also given.:MYHCNMHG648PROCEEDINGS OF THE 14TH IFHTSE CONGRESSOctober 2004Referencesand titanising processes. Proceedings of the EuropeanCongress EUROCORR'96,Nice, France, ASM1. Rudolph G, Schlamp G. Der Eisengehalt von TiC SchichtenInternational, 1996.auf Stahl. Matalloberflache, 1970 (24) 4: 130-132.3. Kasprzycka E, Senatorski J. Tribocorrosion resistant layers2. Huang J, Xiao J, Ouyang J, Zou G and Yuan S. A study onproduced on steel surface in vacuum titanizing process.the powder titanization. Heat Treatment of Metals, 1991 (2):Physico-Chemical Mechanics of Materials (Ukraine), 2004(4): 553-555.3. Zhang L, Li M and Sun X. Study on titanizing in neutral. Senatorski J and Kasprzycka E. Tribological properties ofsalt bath. Heat Treatment of Metals, 1996 (8): 21-24.chromized diffusion layers in conditions of sliding friction. Wang J and Gao G. Powder titanizing of steel under lowand concentrated contact, Tribologia 2002 (6): 1595-1599vacuum. Heat Treatment of Metals, 1997(1): 42-44.5. Kasprzycka E and Tacikowski J. Vacuum titanizing ofCorresponding author: Ewa Kasprzycka, Assistant ProfessorEmail: kasp@ imp.edu.plsteel. R. P. Patent 159325, Warsaw (1993).6. Kasprzycka E. Corrosion resistant layers produced fromMail address: Institute of Precision MechanicsDuchnicka 3, 01-796 Warsaw, Polandmetals vapors (Cr, Ti) under low pressure, Edited byPhone: +48 22 5602911,Institute of Precision Mechanics, Warsaw (2002).7. Kasprzycka E. Corrosion resistance of diffusion layersFAX: +4839120449, +48 226634317, +48 22 5602922produced on steel surface by means of vacuum chromising中国煤化工MYHCNMHG