In the paper we investigate the relationship between the wear intensity of two nodular cast irons and their heat treatment conditions. Disks tempered by austempering and isothermal procedure were used. The wear test was realized by using Pin and Disk tribometer. Measurement of the disks wear, after the contact for duration of 30 min, was done by the PQ meter. The quantity of the wear products in lubricant is determined by the PQ index. The best wear resistance posses the disk isothermally tempering with 30 minutes holding at 390 °C temperature.U ovom radu je ispitivana zavisnost između intenziteta habanja dva nodularna lijeva kao i uvjeta pri njihovoj toplinskoj obradi. Uzorci za ispitivanje nodularnog lijeva su bili poboljšani klasičnim i izotermalnim postupkom. Ispitivanje intenziteta habanja je realizirano uz pomoć Pin on Disc tribometra. Mjerenje pohabanosti diska, nakon trenja u trajanju od 30 minuta, je obavljeno na PQ metru. Količina čestica nastalih kao produkti habanja, u sredstvu za hlađenje i podmazivanje je određena PQ indexom. Najveću otpornost na habanje posjeduje disk izotermalno temperovan na 390 °C u trajanju od 30 minuta

D. Golubović

D. Ješić

M. Gostimirović

P. Kovač

V. Pucovsky

Hrčak - Portal of scientific journals of Croatia

518  METALURGIJA 51 (2012) 4, 518-520D. GOLUBOVIĆ, P. KOVAČ, D. JEŠIĆ, M. GOSTIMIROVIĆ, V. PUCOVSKYWEAR INTENSITY OF DIFERENT HEAT TREATED NODULAR CAST IRONSReceived – Prispjelo: 2011-12-05Accepted – Prihvaćeno: 2012-04-30Preliminary Note – Prethodno priopćenje ISSN 0543-5846METABK 51(4) 518-520 (2012)UDC – UDK 669.13:620.178.1:621.78=111D. Golubović, Faculty of Mechanical Engineering, East Sarajevo, Bosnia and Herzegovina.P. Kovač, M. Gostimirović, V. Pucovsky, Faculty of Technical Science, University of Novi Sad, Serbia.D. Ješić, Faculty of Engineering, University of Banja Luka, Bosnia and Herzegovina.INTRODUCTIONWear intensity of the tribomechanical systems de-pends, not only on physical and chemical characteristics of materials that they are made of, but also, to a signifi -cant extent, on the kind and conditions of their heat treatment.Experimental investigations of tribological and oth-er characteristics of nodular cast irons, that were con-ducted at several laboratories of large industrial systems and universities, have shown that they also depend on conditions of their heat treatment [1, 2, 3]. Measure-ment methodology and election of tribomechanical sys-tem materials is presented in [4].Ductile iron with different nodule counts was used austempered by conventional and successive austem-pering processes at 315 and 375 °C for different period [5]. Specimens with the optimal mechanical properties were used to study the effect of austempering process on the wear behavior of austempered ductile iron (ADI). The paper [6] details the heat treatment of ductile cast iron to yield ADI and also examines its mechanical and abrasive properties. Study of effect of graphite mor-In the paper we investigate the relationship between the wear intensity of two nodular cast irons and their heat treatment conditions. Disks tempered by austempering and isothermal procedure were used. The wear test was realized by using Pin and Disk tribometer. Measurement of the disks wear, after the contact for duration of 30 min, was done by the PQ meter. The quantity of the wear products in lubricant is determined by the PQ index. The best wear resistance posses the disk isothermally tempering with 30 minutes holding at 390 °C temperature.Key words: nodular cast iron, wear, heat treatmentIntenzitet habanja kod različito toplinski poboljšanog nodularnog lijeva. U ovom radu je ispitivana zavisnost između intenziteta habanja dva nodularna lijeva kao i uvjeta pri njihovoj toplinskoj obradi. Uzorci za ispitivanje nodularnog lijeva su bili poboljšani klasičnim i izotermalnim postupkom. Ispitivanje intenziteta habanja je realizi-rano uz pomoć Pin on Disc tribometra. Mjerenje pohabanosti diska, nakon trenja u trajanju od 30 minuta, je obav-ljeno na PQ metru. Količina čestica nastalih kao produkti habanja, u sredstvu za hlađenje i podmazivanje je određe-na PQ indexom. Najveću otpornost na habanje posjeduje disk izotermalno temperovan na 390 °C u trajanju od 30 minuta.Ključne riječi: nodularni lijev, habanje, toplinska obradaphologies on the tribological behavior of austempered cast iron is in [7].In this paper a part of results of tribological investi-gations of two kinds of nodular cast irons characteris-tics, in sliding conditions with and without lubrication, is presented. Investigations were conducted within the framework of a larger scientifi c research program of tri-bological character.MATERIAL AND METHODIn investigation program, two types of nodular cast irons were included: GJL-500-7 and GJL-700-2. Micro-structure of nodular cast iron used in this study is shown in Figure 1 and Figure 2. The material chemical compo-sition is shown in Table 1. Test operations were per-formed on tribometerPin on Disk with linear contact. Nodular cast irons disks were used as samples, tempered by austempering and isothermal procedure.In Table 2 conditions under of the heat treatment of disks made of nodular cast irons GJS-500-7 and GJS-700-2 are shown.The part of the experimental program, which results are presented in this paper, was conducted on tribometer with the sliding speed of 1,3 m/s and external loading F = 20 daN. The conditions of limiting lubrication were realized in all test operations. The study included ex-perimental tests in the duration of 60 minutes of effec-519METALURGIJA 51 (2012) 4, 518-520D. GOLUBOVIĆ et al.: WEAR INTENSITY OF DIFERENT HEAT TREATED NODULAR CAST IRONStive contact. In all the experimental operations lubrica-tion was realized by passing of the lower part of disk through the oil bath, where there was always the same quantity (2-3 ml) of the POI-AR 32K oil. The oil was changed at the same time as the disk and putted into the special containers for further wear products measure-ment.Pins were made of steel C 40E and cast iron GJL-250. Measurement of the disks wear, after the duration contact of 30 min, was done by the PQ 2000 Particle Quantifi er. The quantity of the wear products in lubri-cant was determined by the PQ index.RESULTS AND DISCUSSIONThe procedure of austempering of disks was realized by their heating up to the austenization temperature (900 °C), keeping them at that temperature for 90 min-utes, and quick cooling (in water or air) down to tem-perature of 520 °C.Isothermal tempering of both kinds of disks from nodular cast irons was done by their heating up to the temperature of 900 °C, keeping on that temperature for 60 minutes and quick cooling down to the temperature of 390 °C. At this temperature the formation of marten-site still does not begin. At the temperature of 390 °C disks of both nodular cast irons were kept for 90 respec-tively 30 minutes. In this way the ausferritic microstruc-ture was obtained, that should lead to a smaller wear intensity of disks, namely the elements of tribomechan-ical systems.Indices of wear intensities of disks made of nodular cast iron GJS-500-7 are shown in Figure 3, as a function of the kind of the heat treatment. Two pins were used in the experiments (steel C 40E and cast iron GJL-250).The same type of results obtained for disks made of nodular cast iron GJS-700-2, also for two pins (steel C 40E and cast iron SL250), are shown in Figure 4.The wear intensity on both Figures was obtained by measuring the PQ index and by dividing the obtained values with contact duration time, for both nodular cast irons and two pins.The value of this PQ index is directly proportional to the quantity of wear products (greater than 5 ÷ 10 mi-crons) that is contained in the oil used for lubrication of the contact zone during the sliding of disk along the pin. PQ = K · Q (1)Q is the quantity of wear products per mg of oil pro-duced during sliding of one element of the tribome-chanical system over the other for t minutes. K is con-stant parameter dependent on the many variables of contact condition (sliding speed normal force, type of oil etc.).Table 2 Conditions of heat treatment of disks made of nodular cast ironsType of materialHeat treatment Results of heat treatmentTa °C Tp °C/t in min Average HB The base information of structuresGJS-500-7 /30´900390/30´ 363 Nodules of graphite in the ausferritic matrixGJS-700-2 /30´GJS-500-7 /C520/90´ 302 Deformation nodules of graphite in the martensitic matrixGJS-700-2 /CTable 1 Chemical composition of nodular cast irons GJL-500-7 and GJS-700-2 / wt %Type of material C Si Mn Mg P S CuGJS-500-7 3,85 2,9 0,076 0,035 0,02 0,04 1,3GJS-700-2 3,76 2,35 0,51 0,02 0,004 1,43Figure 1  Microstructure of EN-GJS-500-7, charge 5815-13, magnifi ed 500 times and corroded, with ferrite-perlite baseFigure 2  Microstructure of EN-GJS-700-2, charge 5766-13, magnifi ed 500 times and corroded, with mainly-perlite base520  METALURGIJA 51 (2012) 4, 518-520D. GOLUBOVIĆ et al.: WEAR INTENSITY OF DIFERENT HEAT TREATED NODULAR CAST IRONSPQ index in % is defi ned: IPQ = (PQi /PQc) · 100 % (2)where: PQi - the measured value of the PQ index, name-ly the quantity of wear products in the sample of oil used in realization of contact of Pin and Disk heat treat-ed by isothermal procedure; PQc - the measured value of the PQ index, in realization of contact of Pin and Disk austempered.CONCLUSIONSAccording to obtained results the following conclu-sion can be suggested:•  In contact with steel and cast iron the biggest wear resistance posses the disk isothermally tempered with 30 minutes holding at 390 °C temperature;•  The infl uence of kind of heat treatment on wear intensity depends also on the type of material of the contact pair;•  Differences in the wear intensity of disks made of nodular cast irons GJS-500-7 and GJS-700-2 are smaller in realization of contact with steel than with cast iron pin.In order to determine the optimal conditions of heat treatment of nodular cast irons, from the wear point of view, it is necessary to realize the complex program of investigations. In this program variables would also show the sliding speed and external loading.REFERENCES[1] D. Ješić, Tribological Properties of Nodular Cast Iron, mo-nography Journal of the Balkan Tribological Association, Sofi a, 2000, p 125.[2] H. Mayer, B. Barbezat: Proceeding of the 2nd International Conference on Austempered Ductile Iron, University of Michigan, Ann Arbor (1986), pp. 99-115.[3] K. Brandenberg, Machining Austempered Ductile Iron, Manufacturing Engineering, 128 (2002) 5.[4] B. Sovilj, I. Sovilj-Nikić, D. Ješić, Metalurgija, 50 (2011) 2, 107-111.[5] M. N. Ahmadabadi, H.M. Ghasemi, A.M. Osia, Wear, 231 (1999) 2, 293-300.[6] J. Zimba, D. J. Simbi, E. Navara, Cement Concrete Com-posites, 25 (2003) 6, 643-649.[7] A. R. Ghaderi, M.N. Ahmadabadi, H.M. Ghasemi, Wear, 255 (2003) 1-6, 410-416.Note:  The responsible for English language is Gordana Rašković, The Sworn Court Interpreter, Novi Sad, Serbia.Figure 3  Wear intensity indices for disks made of nodular cast iron GJS-500-7, with diff erent heat treatmentFigure 4  Wear intensity indices for disks made of nodular cast iron GJS-700-2, with diff erent heat treatmentFigure 5 The infl uence of disc material on wear intensity.Both materials had better PQ index in % when pin GJL-250 was used and vice versa. From Figure 2 and Figure 3 it is obvious that best PQ index in % had nodu-lar cast iron GJS-700-2 /C and then GJS-700-2 /30´ with pin GJL-250.In Figure 5 the infl uence of disk material type on wear intensity for both austempering (C) and isothermal tempering procedure (30 and 90 minutes) is illustrated. The highest wear resistance posses the disk isothermal-ly tempered for 30 minutes holding at temperature of 390 °C.

Intenzitet habanja kod različito toplinski poboljšanog nodularnog lijeva

Abstract

Similar works

Full text

Available Versions

Hrčak - Portal of scientific journals of Croatia

HRČAK - Portal of Croatian Scientific and Professional Journals