Rajamangala University of Technology Krungthep, 2,Nanglinchee Road, Tungmahamek, Sathorn, Bangkok, 10120, Thailand

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1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland The Effects of Heat Treatment on Microstructure and Mechanical Properties of AISI 4140 for Base Cutter Cane Harvester Wichan Chuaiphan 1,a, Loeshpahn Srijaroenpramong 2,b and Dumrongrit Pinpradub 2,c 1 Department of Mechanical and Industrial Engineering, Faculty of Engineering, Rajamangala University of Technology Krungthep, 2,Nanglinchee Road, Tungmahamek, Sathorn, Bangkok, 10120, Thailand 2 Department of Metallurgical Technology, Faculty of Education, Rajamangala University of Technology Krungthep, 2,Nanglinchee Road, Tungmahamek, Sathorn, Bangkok, 10120, Thailand a wichan.c@rmutk.ac.th, b loeshpahn.s@rmutk.ac.th, c dumrongrit.p@rmutk.ac.th Keywords: Heating process, Quenching medium, process, Microstructure, Mechanical properties, Base cutter. Abstract. The effects of heat treatment on microstructure and mechanical properties of AISI 4140 for base cutter cane harvester were studied. The effect of heat treatment - i.e. the different quenching medium(water, oil and air mediums) and the different heat treatment condition (quenching, quenching+tempering, cover scrap cast iron+ quenching and cover scrap cast iron+ quenching+tempering) on the on microstructure and mechanical properties (hardness, impact toughness and bend test). The material AISI 4140 was purchased from local market in Thailand and an emission spectroscopy was applied to quantify the amount of elements in steel. The specimens were heat treated in an induction furnace. The resultant microstructure of materials AISI 4140 consists of martensite and retained austenite after quenching all mediums, which quenching in water it have more than in oil and air medium respectively. The microstructure of materials AISI 4140 after tempering process consists of bainitic structure (ferrite and epsilon carbide) and retained austenite, which tempering in water quenching condition it have more than in oil and air quenching condition respectively. The hardness, impact toughness and bended test are according to behavior heat transfer of quenching mediums. The material alloy steel grade AISI 4140 is the good candidates to promote the quenching in water,oil and air medium and must be continuous to tempering process. The technique heating by cover scrape cast iron it was good for protected surface and decreased decarburization on surface of steels. But it is not necessary for control microstructure and mechanical properties. Introduction The sugarcane industries, mostly used the agricultural machinery for cane harvester. The base cutter for cane harvester it is very importance, properties of base cutters must be hardness, toughness, durable, strength and ware resistance. From the requirements of best base cutter it can be improvement by heat treatment process[1]. Thus, the objective of this work is to find out the possibility in using water, oil or air for quenching medium and using cover scrap cast iron technique on materials concurrently with tempering process. Heat treatment is a combination of timed heating and cooling applied to a particular metal or alloy in the solid state in such ways as to produce certain microstructure and desired mechanical properties (hardness, toughness, yield strength, ultimate tensile strength, Young s modulus, percentage elongation and percentage reduction)[2]. Annealing, normalizing, hardening and tempering are the most important heat treatments often used to modify the microstructure and mechanical properties of engineering materials particularly steels.[2,3] Steels are normally hardened and tempered to improve their mechanical properties, particularly their strength and wear resistance[4]. In hardening, the steel or its alloy is heated to a temperature high enough to promote the formation of austenite, held at that temperature until the All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-10/05/16,15:00:36)

2 1060 Advanced Technologies in Manufacturing, Engineering and Materials desired amount of carbon has been dissolved and then quench in oil or water at a suitable rate[5]. Also, in the harden condition, the steel should have 100% martensite to attain maximum yield strength, but it is very brittle too and thus, as quenched steels are used for very few engineering applications. By tempering, the properties of quenched steel could be modified to decrease hardness and increase ductility and impact strength gradually[2]. The resulting microstructures are bainite or carbide precipitate in a matrix of ferrite depending on the tempering temperature. Steel is an alloy of iron with definite percentage of carbon ranges from % [6], plain carbon steels are those containing % [7]. There are two main reasons for the popular use of steel: (1) It is abundant in the earth s crust in form of Fe2O3 and little energy is required to convert it to Fe. (2) It can be made to exhibit great variety of microstructures and thus a wide range of mechanical properties[2]. Alloy steel grade AISI 4140 is one of the commercial alloy steel are widely used for agricultural machinery of Thailand. It used for cutting tool of cane harvester, cane planter, cassava stem and cassava planter. Mainly, agriculturist used it on the commercial condition, they are found the cutting tools are tool life short. For this reason, the authors are investigate the effects of heat treatment on microstructure and mechanical properties of AISI 4140 for base cutter cane harvester for supported agriculturist of Thailand. Experimental material and procedure The material used for this study is a low alloy steel grade AISI 4140 for base cutter cane harvester. The chemical compositions of material is given in Table 1. The material are machined to the dimension of 250x85x6 mm, cutting edge 30 and drill 6 point according to the standard the base cutter cane harvester is shown in Fig.1. Fig. 1 Specimen base cutter for sugar cane harvester Table 1 Chemical composition of materials (wt%) Element (wt%) Materials C Si Mn P Cr Mo S Bal. Standard Fe AISI max max Specimen Fe Heat treatment The specimen preparation under heat treatment process was carried out in line with the standard procedure outline below[8]. Three sets of specimen were prepared in this way: (1) set water quenching, (2) set oil quenching and (3) set air quenching. Each set consist of four condition are shown detail in Table 2. The heat treatment process of each condition are shown in Fig.1.

3 Advanced Materials Research Vols Table 2 Condition of Heat Treatment and specimen Set Water Quenching W1 Oil Quenching O1 Air Quenching A1 Condition of Heat Treatment Water Quenching+ W2 Oil Quenching+ O2 Air Quenching+ A2 Cover cast iron scrap and Water Quenching W3 Cover cast iron scrap and Oil Quenching O3 Cover cast iron scrap and Air Quenching A3 Cover cast iron scrap and Water Quenching+ W4 Cover cast iron scrap and Oil Quenching+ O4 Cover cast iron scrap and Air Quenching + A4 Fig. 2 Schematic illustration of heat treatment process for prepared specimen

4 1062 Advanced Technologies in Manufacturing, Engineering and Materials Condition of heat treatment specimens Condition W1,O1and A1. Heat the furnace to 200 C; load samples into the furnace and continuous heating to 860 C; holding for 30 min at 860 C. Next step take out the samples and water quenching(for W1), oil quenching(for O1) and air quenching(for A1). Condition W2, O2 and A2. Heat the furnace to 200 C; load samples into the furnace and continuous heating to 860 C; holding for 30 min at 860 C. Next step take out the samples from furnace and water quenching(for W2), oil quenching(for O2) and air quenching(for A2), cool to room temperature. And continuous tempering process; load samples after water, oil and air quenching inside tempering furnace, heating to tempering temperature at 400 C; hold for 30 min at 400 C. After holding for 30 minutes, shut off the furnace door to allow the samples to cool inside the furnace until to room temperature. Condition W3,O3and A3. Heat the furnace to 200 C; load samples into the furnace and use scrap cast iron cover the samples under heating together, continuous heating to 860 C; holding for 30 min at 860 C. Next step take out the samples and water quenching(for W3), oil quenching(for O3) and air quenching(for A3) until samples cool to room temperature. Condition W4,O4and A4. Heat the furnace to 200 C; load samples into the furnace and use scrap cast iron cover the samples under heating together, continuous heating to 860 C; holding for 30 min at 860 C. Next step take out the samples and water quenching(for W4), oil quenching(for O4) and air quenching(for A4) until samples cool to room temperature. And next step continuous tempering process; load samples after water, oil and air quenching inside tempering furnace, heating to tempering temperature at 400 C; hold for 30 min at 400 C. After holding for 30 minutes, shut off the furnace door to allow the samples to cool inside the furnace until to room temperature. Microstructure and Mechanical testing The metallographic examinations, several specimens were prepared from all heat treatment conditions. The specimen were prepared by grinding using 150, 220, 320, 400,500, 800, 1000 and 1200 grits of SiC paper, followed by the final polishing 0.3 µm Al 2 O 3 powders. Then, the specimens were etched in solution of 2 %v/v nital. The microstructure are analyzed using an optical microscopy(om). The mechanical properties tests samples include Vicker hardness, Bending U shape test and Charpy V notch impact test. Impact tests are performed with sub-size specimens (55 mm x 6 mm x 6 mm) at room temperature. Results and discussion Microstructure Fig. 3 shows the microstructure of untreated specimen AISI 4140 grade, it is a combination of ferrite and pearlite. The microstructure of heat treatment set water quenching shown in Fig.4(a)-(d). For Fig.4(a) microstructure consists of martensite and retained austenite[9], while the microstructure of the heat treatment condition quenching+tempering and condition cover scrap cast iron+ quenching are shown in Fig. 4 (b)-(c) respectively. It were found that microstructure combine of bainitic structure (ferrite and epsilon carbide) and retained austenite[9]. For the heat treatment condition cover scrap cast iron+ quenching+tempering was expressed in Fig. 4(d), according to these microstructure it is consists of cementite precipitate and ferrite matrix[10]. For this resulting to confirm effect of tempering process it can be control microstructure of steels. Fig. 5(a-d) and Fig.6(a-d) are shown the microstructure of heat treatment set oil quenching and air quenching respectively. They were observed microstructure slightly different compare with the heat treatment set water quenching all condition. However, the martensite structure under condition

5 Advanced Materials Research Vols oil quenching it was contain more than condition air quenching. This was due to oil medium it was heat transfer better than air medium[10]. Fig. 3 Microstructure of material AISI 4140 commercial grade Fig. 4 Microstructure of set water quenching (a) quenching, (b) quenching+tempering, (c)cover scrap cast iron+ quenching and (d) cover scrap cast iron+ quenching+tempering

6 1064 Advanced Technologies in Manufacturing, Engineering and Materials Fig. 5 Microstructure of set oil quenching (a) quenching, (b) quenching+tempering, (c)cover scrap cast iron+ quenching and (d) cover scrap cast iron+ quenching+tempering Fig. 6 Microstructure of set air quenching (a) quenching, (b) quenching+tempering, (c)cover scrap cast iron+ quenching and (d) cover scrap cast iron+ quenching+tempering

7 Advanced Materials Research Vols Hardness test The variation of hardness against type of quenching medium (water quenching, oil quenching and air quenching) and against different heat treatment condition (quenching, quenching+tempering, cover scrap cast iron+ quenching and cover scrap cast iron+ quenching+tempering) are shown in Fig. 7. When discuss hardness value of samples different quenching medium. It was found that the specimen water quenching has a hardness higher than oil quenching and air quenching respectively. This was due to effect of cooling rate of quenching medium[3]. Furthermore, when discuss hardness value against different heat treatment condition. It was clearly seen that the specimens in quenching condition has a hardness value higher than the quenching+tempering condition, cover scrap cast iron+ quenching condition and cover scrap cast iron+ quenching+tempering condition respectively of three quenching medium. The difference of hardness in difference heat treatment condition these can be explain to the tempering process, general observation for normal steels that hardness decreases[9]. While, the cover scrap cast iron condition it is a general observation for protect decarburization on surface steel. However, the hardness value of the cover scrap cast iron condition are accept in standard of steels[11]. Impact Toughness test Fig. 7 Variation of hardness against different of heat treatment The variation of impact strength against type of quenching medium and against different heat treatment condition are shown in Fig. 8. It was found that the specimens under air quenching it has impact toughness higher than oil quenching and water quenching respectively. This was due to air quenching medium it is low cooling rate more than oil and water quenching medium, it cause the low hardness properties because the cooling rate can be control hardness properties of heat treatment steels[3]. Therefore, at the high level hardness will low impact toughness. When discuss impact toughness under different heat treatment condition. It was clearly seen that the impact toughness lowest of specimen quenching condition and impact toughness increases of quenching+tempering, cover scrap cast iron+ quenching and cover scrap cast iron+ quenching+tempering respectively. When considerate this results it was seen relationship between hardness and impact toughness which is a general observation for normal steels[12].

8 1066 Advanced Technologies in Manufacturing, Engineering and Materials Bending Test Fig. 8 Variation of Impact toughness against different of heat treatment In the bending test, on the specimen of different quenching medium and against different heat treatment condition present in Fig. 9. When considerate specimens after bending test, it was found that specimens after water, oil and air quenching, without tempering process crack and fracture all specimens are shown in Fig. 9 (a). This was because specimen was high hardness and high brittleness. On the other hand, specimen under tempering and cover scrap cast iron condition heat treatment all specimen not crack and not fracture are shown in Fig. 9(b). This result can be expand to effect of hardness value from different heat treatment. Fig. 9 Bended test specimen against different of heat treatment (a) example specimens fracture and (b) example specimen not fracture Conclusions From the results of investigation on the effect of heat treatment on microstructure and mechanical properties of alloy steel grade AISI 4140 for base cutter cane harvester, the following conclusions were made.

9 Advanced Materials Research Vols The microstructure of materials AISI 4140 consists of martensite and retained austenite after quenching all mediums, which quenching in water it have more than in oil and air medium respectively. 2. The microstructure of materials AISI 4140 after tempering process consists of bainitic structure (ferrite and epsilon carbide) and retained austenite, which tempering in water quenching condition it have more than in oil and air quenching condition respectively. 3. The hardness, impact toughness and bended test are according to behavior heat transfer of quenching mediums. 4. The material alloy steel grade AISI 4140 is the good candidates to promote the quenching in water,oil and air medium and must be continuous to tempering process. 5. The technique heating by cover scrape cast iron it was good for protected surface and decreased decarburization on surface of steels. But it is not necessary for control microstructure and mechanical properties. Acknowledgements The authors would like to thank the Research & Development Institute, Department of Industrial Engineering, Faculty of Engineering and Department of Metallurgical Technology, Faculty of Education, Rajamangala University of Technology Krungthep for supporting this project. References [1] T. Senthilkumar and T.K. Ajiboye: J. Min. Mater. Charact. & Eng. Vol. 11(2) (2012), p. 143 [2] D.A. Fadare, T.G. Fadara and O.Y. Akanbi: J. Min. Mater. Char. & Eng. Vol. 10(3) (2011), p. 299 [3] A. Calik: J. Phys. Sci. Vol. 4(9) (2009), p. 514 [4] M.S. Htun, S.T. Kyaw and K.T. Lwin: J. Met. Mater. and Min. Vol. 18(2) (2008), p. 191 [5] National Metal and Materials Technology Center, Pathumthani, Thailand: J. Met. Mater. and Min. Vol. 21(1) (2011), p. 67 [6] V.B. John, in: Introduction to Engineering Materials, edtied by Macmillan Publishing Company Ltd., (1980) [7] A.J. Alawode, in: Effect of Cold Work and Stress Relief Annealing Cycle on the Mechanical Properties and Residual Stresses of Cold-Draw Mild Steel Rod. M. Engineering Thesis, Mechanical Engineering Department, University of Ilorin, Nigeria. (1995) [8] G.E. Totten, in: Steel Heat Treatment: Metallurgy and Technologies. Taylors & Ferancies Group, NY (2007) [9] ASM International, in: ASM Handbook: Heat Treatment, Vol. 4 American Society for Metals Park, Ohio (1991) [10] P.O. Offer, C.C. Daniel and D.O.N. Obikwelu: Nigerian Journal of Technology Vol. 29(2) (2010) [11] V. Singh: Heat Treatment of Metals, Standard Publishers Distributors, Delhi (1998) [12] R.C. Fan, M. Gao, Y. Ma, X. Zha, X.C. Hao and K. Liu: J. Mater. Sci. Technol. Vol. 28(11) (2012), p.1059

10 Advanced Technologies in Manufacturing, Engineering and Materials / The Effects of Heat Treatment on Microstructure and Mechanical Properties of AISI 4140 for Base Cutter Cane Harvester / DOI References [12] R.C. Fan, M. Gao, Y. Ma, X. Zha, X.C. Hao and K. Liu: J. Mater. Sci. Technol. Vol. 28(11) (2012), p /S (12)60173-X