Simulation of Plasma Transferred ARC (PTA) Hardfaced on Structural Steel with Titanium Carbide

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1 Computers & Applied Sciences (JEC&AS) ISSN No: Volume, No.4, April 013 Simulation of Plasma Transferred ARC (PTA) Hardfaced on Structural Steel with Titanium Carbide S.Balamurugan, Assistant Professor, Department of Mechanical Coimbatore Institute of Technology Coimbatore, INDIA N.Murugan, Professor, Department of Mechanical Coimbatore Institute of Technology Coimbatore, INDIA ABSTRACT Plasma Transferred Arc (PTA) hardfacing performed to improve the surface properties of metallic machine parts locally. Hardfacing process was applied when the surface to be damaged by wear due to hard minerals. The analyses of PTA hardfacing on structural steel with titanium carbide (TiC) are employed using by finite element technique. The aim of this work is to compare the simulated measured weld bead geometry values with experimental results at various heat input conditions and showing good agreement. Key Words: PTA hardfacing, FEM, validation 1. Introduction It was reported that wear resistance could be improved when hard particles were embedded in a tough, metallic matrix [1, ]. Hardfacing is a technique used to improve the surface properties of metallic mechanical parts, such as the resistance against wear and correction. Surface properties and quality depend upon the selected alloys and deposition processes [3, 4]. Depending on the applied technique, common problems encountered in hardfacing are combination of a poor bonding of the applied surface layer to the base material, the occurrence of porosity of the thermal distortion of the workspiece, the mixing of the layer with the base material and the inability of a very local treatment [5]. According to the literature, coatings obtained by PTA present a very good alternative to other hardfacing processes, such as conventional techniques or more recent ones like laser cladding [6, 7]. A significant advantage of PTA surfacing over traditional surface welding processes arises from the fact that the consumable material used is in the powder form. This fact enables a wide range of composition for the coating materials and even mixtures of different material powders. Finite Element (FE) simulation of welding consists of transient thermal analysis to predict the hardfaced structures. The results of simulation of welding can be used to explain the physical essence of the complex phenomena explicitly and can be used for optimizing the process parameters. Therefore, FE simulation of the welding process using ANSYS software has great significance from both theoretical and practical aspects [8]. It is observed that finite element coupled field thermal and structural analytical studies for evaluating residual stresses using ANSYS birth and death analysis have been carried out on butt and fillet welds, but not on hardfacing deposits [9, 10]. Hence, finite element analysis using ANSYS birth and death technique is used in the present work to identify the correct welding parameters like welding current, welding voltage, welding speed, base metal preheat and inter pass temperature requirements, to facilitate crack-free hardfacing and limiting the welding residual stress. The finite element analysis of hardfacing of titanium carbide on structural steel plate is performed using ANSYS software by applying different heat input conditions. The thermal diffusivity of the base material plays a large role - if the diffusivity is high, the material cooling rate is high and the HAZ is relatively small. Alternatively, a low diffusivity leads to slower cooling and a larger HAZ. The amount of heat inputted by the hardfacing process plays an important role. To calculate the heat input for arc welding procedures, the following formula is used: Where Q = heat input (kj/mm), V = voltage (V), I = current (A), and S = welding speed (mm/min). The efficiency depends on the welding process used. For PTA hardfacing efficiency is taken as 0.6 [11] The objective of this work is to compare the experimentally measured weld bead geometry with simulated results at various heat input conditions.. Matrial Properties The chemical composition and mechanical properties are shown in Table 1. The temperature dependent thermal properties of base substrate and TiC are shown in Table. 10

2 Computers & Applied Sciences (JEC&AS) ISSN No: Volume, No.4, April Finite Element Simulation A substrate structural steel plates with dimensions 150 mm x 100 mm x 0 mm thickness and 100 mm X 1 mm X mm hardfaced material placed on the substrate. Hardfaced process is simulated a single pass. The eight-node brick elements are used in meshing the model. To simulate the moving heat source element birth and death technique of ANSYS was used. The element type SOLID70, which has a single degree of freedom, was used for the thermal analysis. For the structural analysis the element type SOLID45, with three translational degrees of freedom at each node, was used. Constraints (all degrees of freedom) are placed at both ends of the plate, as during hardfacing these ends are tack welded to prevent any distortion. Fig.1 shows the meshed model. 4. Experimental Procedure Using PTA hardfacing system, Titanium Carbide (TiC) was deposited onto the structural steel plate of size 150 mm X 100 mm X 5 mm. This was done by changing the welding parameters to achieve different heat input conditions: Low, medium and high. Single hardfacing bead was laid on each plate. Samples were prepared from each hardfaced plate by cutting them at their centre perpendicular to hardfacing direction. Standard metallurgical procedures were employed to prepare the samples from PTA hardfacing deposited at different heat input conditions as shown in Table. 3. Hardfaced plate and typical cross section are shown in Fig. and Fig.3 respectively. Table.1: Chemical Composition and Mechanical Properties of Structural Steel and TiC Elements, Weight % Material Used C Si Mn S P Mg Ti Fe 1 IS:06 (Base Metal) bal Base Metal Titanium Carbide (TiC) (PTA Powder) Hardness Hardfaced Metal Tensile Strength Yield Strength 18 HRC 56HRC 485 MPa 75 MPa Table. The temperature dependent material properties of substrate and TiC. IS 06 MILD STEEL TiC Temp( 0 C) K ( W/m 0 C) C (J/kg 0 C) K(W/m 0 C) C(Jkg 0 C) (average of C to )

3 Computers & Applied Sciences (JEC&AS) ISSN No: Volume, No.4, April 013 Fig.1Meshed model of the PTA hardfaced plate Fig 1. Photograph of hardfaced plate Fig. Typical cross section of hardfaced plate Table. 3 PTA Hardfacing Experimental Conditions Parameters Heat Input, I S F H T kj/mm Low Heat Input(LHI) Medium Heat Input(MHI) High Heat Input(HHI) I =Welding Current (amps); S = Welding Speed (mm/min); F = Powder feed rate (gm/min); Oscillation Width (mm); T = Pre heat temperature ( 0 C). H = 5. Result And Discussion The results of simulation obtained for three heat input condition as shown in the Table. 4. Transverse section is taken from Q-Slice option available in ANSYS, used to find the penetration and longitudinal temperature plots are used to find bead width of the weld profile. From the Figures and 3, it is understood the heat input increases, penetration increases. From the simulated results, it is concluded that bead width and penetration are strongly affected by applied heat input during the TiC hardfacing of plates. The measured bead geometry parameters of the plates are compared with simulation results which are presented in Table 4 and Figure 4. Thus to obtain a good weld bead profile, selection of process parameters is important. It is evident that, Finite Element results are less deviated when compared to experimental results and these deviations are due to the assumptions made in finite element analysis. 1

4 Computers & Applied Sciences (JEC&AS) ISSN No: Volume, No.4, April 013 Fig. Typical Temperature Contour plot of hardfaced plate. Fig.3 Typical Temperature Counter plot cut the transverse direction of hardfaced plate Table 4 Comparison of measured and predicted bead geometry of hardfaced plate. 1 3 Heat Input, (kj/mm) LHI MHI HHI Exp Penetration(mm) FEM % Error Exp Bead width (mm) FEM % Error

5 Computers & Applied Sciences (JEC&AS) ISSN No: Volume, No.4, April 013 Fig.4 Comparison of effect of heat input on bead width and penetration 6. Conclusion Three dimensional thermal models is employed to predict the bead geometry parameters such as penetration and bead width and the predicted results are compared with experimental results. 7. References [1] U.Draugelats, B. Bouaifi and T. Plegge. Weld Res. Abroad, 4,(11), pp , [] A. K. Jha, B. K. Prasad, R. Dasgupta, et al.; J.Mater.Eng.Perform, 8, (), pp , [3] J.R.Davis and Associates, Hardfacing, weld cladding and dissimilar metal joining in; ASM Handbook Welding, Brazing and Soldering, Vol.6, 10 th Ed, ASM metals Park, OH, 1993, pp [4] E.Lugscheider,U.Morkramor, A. Ait- Proceeding of the Fourth National Thermal Spray Conference, Pittsburgh, PA, USA, Makideche, Advances in PTA surfacing, [5] Wolfgang Whal, Stuttgart, Trends for Hardfacing, uploads/1683/drwhal006.pdf [6] D Oliveira, A.S.C.M., Yaedu, A.E and Silva P..S.C.P, Influence of dilution on microstructure and mechanical properties of cobalt- based alloy depositedd by Plasma Transferred Arc Welding, International Conference on Advanced materials, their processes and applications, materials week, Muchen, 00. [7] Agustin Gualo Hernan G. Svoboda Estela S.Surian and Luis A. de vedia, Effect of welding procedure on wear behavior of a modified martenstic tool steel hardfacing deposit, Materials & Design, Elsevier, 011. [8] Ivana Vasovic, Dragi Stamenkovic, Finite element analysis of residual stress in butt welding two similar plates, Scientific Technical Review, Vol. LIX, No.1, 009, pp [9] Xiangyang Lu, Tasnim Hassan, Finite residual stresses in butt and socket welded joints, Transactions, SMiRT 16, Paper No. 1983, 001 [10] ASM ready reference: Thermal properties of metals, ASM [ 11] FU Yue-chun, SHI Nan-lin, Zhang De-zhi, YANG Rui. Preparation of SiC/Ti composites by powder cloth technique[j]. The Chinese Journal of Nonferrous Metals, 004, 14(3): (in Chinese) 14