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1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 116 EFFECT OF THE PROCESS PARAMETERS ON GEOMETRICAL CHARACTERISTICS OF THE PARTS IN DIRECT METAL DEPOSITION: A REVIEW 1 Subodh Kumar, 2 Ajit Kumar Singh Choudhary, 3 Rakesh 1 Department of Production Engineering, B. I. T. Sindri, Dhanbad, Jharkhand(India) 2 Department of Mechanical Engineering, Manav Rachna International University, Faridabad (India) 3 Department of Production Engineering, B. I. T. Sindri, Dhanbad, Jharkhand(India) ABSTRACT Direct Metal Deposition (DMD) is a blending of five common technologies: laser, CAD, CAM, Sensor and Powder Metallurgy. It builds metallic parts layer by layer directly from the CAD data. The process has been widely used in manufacturing, part repairing/coating and metallic rapid prototyping. However, success of this technology depends mainly upon the geometrical quality of the components produced, which in fact strongly dependent upon various parameters such as laser power, beam diameter, scanning speed, powder mass flow rate, etc. This paper presents a review on the DMD process, its parameters and influence of the parameters on geometrical characteristics of the components. Keywords: Direct Metal Deposition, CAD, CAM, Sensor, Powder Metallurgy, Process Parameters, Product Characteristics. 1. INTRODUCTION Direct Metal Deposition (DMD), is one of the material additive rapid manufacturing techniques which in fact is the blending of five common technologies – Laser, CAD, CAM, Sensors and Powder metallurgy [1, 2]. This technique has shown tremendous potential for different fields of application such as rapid manufacturing , parts repairing etc.[4, 5]. The process is known by several names, most of which are trademarks of various machine manufacturers or research establishments, these include laser metal deposition (LMD), direct laser deposition (DLD), laser engineered net shaping (LENS), laser cladding, laser deposition welding and powder fusion welding. In DMD, laser beam is used to form a melt pool on a metallic substrate, into which powder is fed. The powders get melted by the heat of laser and form a deposit on the substrate by fusion bonding. INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 117 Once a layer is deposited, the powder delivery nozzle and focusing lens assembly is incremented up, and another layer is deposited. The process is repeated until the part is complete. When the process is correctly controlled a wide range of metal like Titanium, Nickel, Cobalt, Steel alloys etc. can be deposited. The as-deposited microstructure is similar to that of an as-welded structure, so post- deposition heat treatment may be required.  One of the important features for of the DMD process is the fabrication of parts with accurate geometries. The dimensional accuracy of the parts produced by DMD technique depends on the uniformity and repeatability of deposition height. This can only be achieved if the laser retracted distance is equal to the height of the layer deposited. This fact necessitates knowing in advance the layer thickness deposited so that laser processing head can be retracted by equal distance. This paper, therefore, focuses on a review of the process and various research efforts made to find out the effects of the DMD parameters and the relationship between process parameters and product/process characteristics. Fig1. shows a schematic of the process. Fig.1: Schematic Diagram of the DMD process 2. LBDMD PROCESS PARAMETERS AND PRODUCT CHARACTERISTICS 2.1 Process Parameters In DMD, a large number of operating parameters govern the process. Understanding the relationship between these parameters and their effects on the process are crucial to the geometrical and physical quality of the parts. In general, these parameters are classified into four groups as shown Table 1. Table 1: Main Process Parameters  Laser Motion Device Powder Feeder Materials - Average power - Spot size - Wavelength - Pulsed/CW - Beam profile - Laser pulse shaping - Relative velocity - Relative acceleration - System accuracy - Powder feed rate - Inert gas flow arte - Nozzle specification - Powder stream Profile -Substrate geometry - Composition - Powder size - Surface tension - Metallurgical, thermo-physical and optical properties
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 118 2.2 Parts Quality The properties of the deposited layers using the DMD process can be classified in the following four groups: geometrical, mechanical, metallurgical and qualitative properties. Table 2 shows the parameters which contribute to these four groups. Some of these may be inter-related; for instance, the wear resistance can be affected by hardness, the microstructure, the number of cracks and their depth and direction, and the bonding between base materials and substrate. Table 2: Clad properties  Geometrical Mechanical Metallurgical Qualitative - Clad dimension - Dilution - Roughness - Hardness Distribution - Residual stress - Wear resistance - Tensile strength - Microstructure - Dilution - Grain size - Homogeneity - Corrosion resistance - Porosity - Cracking 3. PROCESS PARAMETERS AND GEOMETRICAL PROPERTIES In order to comprehend in detail the process nature and furthermore, control the process outcome, a number of numerical and analytical models have been developed for simulation of the process. One of the first attempts to model the process was performed by Picaso et al. , who developed a simplified model for predicting the process speed and the powder feed rate for the specified laser power, beam diameter and clad height. Their work concentrated on the multi-pass laser cladding and used analytic three dimensional modelling, having assumed however that powder was pre deposited on the substrate. Kiecher et al.  attempted to relate build parameters to deposition using an energy density approach. They integrated the supplied energy over the area of the layer to be built and were able to show that deposition varied linearly with energy density. Their approach only studied two build parameters – laser power and velocity- and did not consider material input, which must also influence deposition. Toyserkani et al.[11,12] investigated the laser cladding process by using transient three dimensional finite element modelling. The effect of the powder feed rate as well as the travel speed were investigated in  where as the laser pulse shaping effect was investigated in . These investigations have showed that the clad height increases by decreasing the process speed, or by increasing the powder feed rate and the laser pulse energy or the laser pulse frequency. Kummailil et al. studied the effect of laser power, scan velocity, hatch spacing and powder mass flow rate on deposition using two level fractional designed experiment to develop simple relationships between build parameters and deposition. Their approach did not consider material properties. Result of their designed experiment suggests that increasing mass flow rate or laser power increases deposition, while increasing hatch spacing or scan velocity decreases deposition. According to them mass flow rate and scan velocity seem to have the highest effect on deposition. Also, deposition appears to be related to the product of energy per unit area and mass flow rate through a power relationship as:
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 119 a xu PAm Z ∆ ∝ (1) where P is the power; A, the absorptivity; m, the mass flow rate rate; ∆x, the hatch spacing and u, the scan velocity. Apart from these four build parameters studied in , Kumar et al;  considered other builds parameters and material properties also for developing their generalized theoretical model to calculate the layer thickness. They used dimensional analysis as their modelling tool. For physical modelling they have considered DMD as a function of both material delivery and energy delivery. Accordingly, they developed material delivery model and energy delivery model separately considering their associated factors and finally combined them as: 4 1 4 4 1 2 )( − ∆ = u PPm TC h CZ c mp f DMD ρ ε Where ZDMD is the layer thickness, ρ the powder density, m powder flow rate, u laser scan velocity, ε absorptivity, hf heat of fusion, Cp specific heat capacity, ∆Tm temperature difference, P laser power, Pc critical power and C dimensionless constant. The validity of this generalized model has been verified from experimental data of H13 and Ti material and it was found in good agreement with experimental finding by other researcher. The error of prediction using this model is 12.899%. Both the model developed in  and , deposition appears to be through a power relationship within the range of parameters tested. In model by , it seems that increasing velocity by one unit should be approximately equivalent to decreasing the mass flow rate by one unit, however, it is not so in model developed by . It is probably due to the other build parameters and material properties considered in same model. Considering surface tension as a dominant phenomenon, Lalas et al. developed an analytical model to estimate the clad width, depth and height. They first calculated the liquid clad volume per unit length by the powder feed rate assuming the substrate is still solid. They then considered substrate and powder both liquefied and estimated the clad geometry. Their model estimates the clad width with a deviation of 1.5% for high powder feed rate and 13% with low powder feed rate when compared with the experimental results. Zhu et al. fabricated thin wall parts of stainless steel 316L with different laser and powder defocusing distances. The found that adopting the powder focussed below the substrate and laser focussed above the substrate process can improve the surface quality. Smuggerskey et al. conducted a set of statistically designed experiments with LENS apparatus consisting of 1.8 kW continuous wave Nd:YAG laser to sort through the various process parameters and identify significant process variable for improving surface finish. With their test material as stainless steel 316L their experimental result suggests that the optimal surface finish is primarily a function of laser power and powder volume. The best surface finish (8 micrometers) should be achieved at an intermediate power of 325 watts, an intermediate flow rate, and will be independent of travel speed. However, Ludovico et al; , performed roughness test on Nickel alloy, using six axis machine equipped with a welding head and with a CO2 laser with a maximum power of 3kW. Result for roughness showed that it increases with powder flow rate and laser power but it decreases with scanning speed. It means that good surface sample can be obtained setting the powder flow rate and laser power to the minimum value and the scanning speed to the maximum value. (2)
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 120 The size of the molten pool is also influenced by the heat stored in the substrate or in the previously deposited material. If the heat loss occurs very quickly, the width of the molten pool decreases, on contrary, if the heat loss occurs very slowly, the width of the molten pool increases. Setting the laser power and the processing speed, the width of the molten pool can be determined. This is important because size of the molten pool affects the properties of the final product. Vasinonta et al. has provided a more fundamental understanding of the dependence of melt pool size on process parameters by presenting melt pool length prediction for thin walled structures in the form of “process map” based on non-dimensional process variables. They demonstrated that melt pool length is a strong function of laser power and velocity, and a weak function of preheat temperature. Fig. 2: Parameters interaction and their effect on geometrical characteristics of part 4. CONCLUSION Various parameters involved in Direct Metal Deposition process has been categorized on the basis of laser, motion drive of the system, powder feeder and materials properties. Also, the property of the deposited layer has been classified into different groups such as geometrical, mechanical, metallurgical and qualitative properties. Interaction of these parameters such as dilution, laser power distribution, powder flow rate etc has been discussed and finally the research conducted by various authors and their methodology in terms of geometrical characteristics of the parts produced through Direct Metal Deposition has been reviewed and presented in the table.3. Direct Metal Deposition Energy Delivery System & associated factors: Laser power Critical power to initiate melting Absorptivity Focal point position Spot size Temperature difference Specific heat capacity Heat of fusion Material Delivery System & associated factors: Powder shape, size Nozzle geometry Nozzle stand-off-distance Shielding gas flow rate Feeder type Powder composition Powder density Thermal property of powder Laser Power Density Powder flow rate Melt pool temperature Dilution Laser scan velocity Clad heightClad width Cladding rate Overlap factor Surface finish Geometrical characteristics Miscellaneous factors: Powder catchment efficiency Substrate temperature Interaction time Microstructure Layer bonding
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 121 Table 3: Summary of the reviewed papers S. No. Author Title of the Paper Year Parameters considered Characteristics of the parts studied Methodology 1. Picaso et.al A simple but realistic model for laser cladding 1994 Process speed and the powder feed rate Clad height Analytic three – dimensional modelling 2. Kiecher et al. The laser forming of metallic components using particulate materials 1997 Laser power and scanning speed Deposition Energy density approach. 3. Smugeresky et. al Laser Engineered Net Shaping(LENSTM ) Process: Optimization of Surface finish and Microstructural Properties 1997 Laser power and powder volume Surface finish Design of Experiment *4. Lewis et.al Practical considerations and capabilities for laser assisted direct metal deposition 2000 laser power and the processing speed Melt pool size 5. Vasinonta et.al A process map for consistent build conditions in the solid freeform fabrication of Thin – Walled Structure 2001 Laser power and velocity Melt –Pool length Process Map 6. Toyserkani et. al Three- dimensional finite element modelling of laser cladding by powder injection: effect of powder feed rate and travel speed on the process 2003 Powder feed rate and travel speed Clad height Transient three dimensional finite element modelling 7. Toyserkani et. al Three- dimensional finite element modelling of laser cladding by powder injection: effect of laser pulse shaping on the process 2004 Laser pulse shaping Clad height Transient three dimensional finite element modelling 8. Kummailil et.al Effect of select LENSTM processing parameters on the deposition of Ti- 6Al-4V 2005 Laser power, scan velocity, hatch spacing and powder mass flow rate Clad height Two level fractional designed experiment 9. Lalas et. Al An analytical model of the laser clad geometry 2007 Powder feed rate Clad geometry Analytical modelling 11. Zhu et. Al The influence of laser and powder defocusing characteristics on the surface quality in laser direct metal deposition 2012 laser and powder defocusing characteristics Track height & Surface quality Theoretical calculation, adjusting relative locations of focus points 10. KumarS et. Al Determination of layer thickness in direct metal deposition using dimensional analysis 2013 Both build parameters and material properties Layer thickness Dimensional analysis 12. Ludovico et.al Experimental analysis of the direct laser metal deposition process 2013 powder flow rate and laser power Roughness Design of Experiment 5. REFERENCES  Krar S (2007) Direct metal deposition: manufacturing at the speed of light. p 3  Bieler TR et al (1998) Trends in materials and manufacturing technologies for transportation industries and powder metallurgy research and development in th transportation industry. Wiley, p. 406.  Xiuli H, Lijun S, Gang Y et al (2011) Solute transport and composition profile during direct metal deposition with coaxial powder injection. Appl Surf Sci 258:898-907.  Santos EC, Shiomi M, Osakada K, Laoui T (2006) Rapid manufacturing of metal components by laser forming. Int J Mech Tool Manuf 46:1459-1468.
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 116-122 © IAEME 122  Kumar A, Paul CP, Pathak AK (2012) A finer modelling approach for numerically predicting single track geometry in two dimensions during Laser Rapid Manufacturing. Opt Laser Technol 44:559-565.  Pinkerton AJ, Wang Li L (2008) Component repair using laser direct metal deposition. Proc ImechE Part B: J Eng Manuf 222:827-835.  Schneider M, (1998) “Laser cladding with powder: effect of some machining parameters on clad properties”, Ph.D thesis University of Twente, Enshede, The Netherlands  Kumar S, Sharma V, Kumar, Choudhary AKS, et al (2013) Determination of layer thickness in direct metal deposition using dimensional analysis: Int J Adv Manuf Technol, 67:2681-2687.  Picaso M. Marsden CF, Wagniere JD, Frenk A, Rappaz M (1994) A simple but realistic model for laser cladding. Metall Mater Trans (25B): 281-291.  Kiecher, D.M. and Smugeresky, J.E (1997) The laser forming of metallic components using particulate materials. Journal of materials 49(5):51-54.  Toyserkani E, Khajepour A, Corbin S (2003) Three- dimensional finite element modelling of laser cladding by powder injection: effect of powder feed rate and travel speed on the process. J Laser Appl 15(3): 153-160.  Toyserkani E, Khajepour A, Corbin S (2004) Three- dimensional finite element modelling of laser cladding by powder injection: effect of laser pulse shaping on the process. Opt Laser Eng. 41: 849-869.  Kummaili J,Sammarco C, Skinner D, Brown C. A, Rong K (2005) Effect of select LENSTM processing parameters on the deposition of Ti-6Al-4V. J of Manufacturing Processes 7(1): 42-50.  Lalas C, Tsirbas K, Salonitis K, Chryssolouris G (2007) An analytical model of the laser clad geometry. Int J Adv Manuf Technol 32:34-41.  Zhu Gangxian, Li Dichen, Zhang Anfeng, Pi Gang, Tang Yiping (2012) The influence of laser and powder defocusing characteristics on the surface quality in laser direct metal deposition. Optics & Laser Technology 44:349-356.  Smugeresky J.E, Keicher D.M, Romero J.A, Griffith M.L and Harwell L.D (1997) Laser Engineered Net Shaping(LENSTM ) Process: Optimization of Surface finish and Microstructural Properties. OSTI:SAND-97-8652C.  Ludovico A. D., Angelastro A and Campanelli S. L(2013) Experimental analysis of the direct laser metal deposition process. www.intechopen.com.  Lewis G.K & Schlienger E (2000) Practical considerations and capabilities for laser assisted direct metal deposition. Materials and Design 21(4):417-423.  Vasinonta A., Beuth J. L., Griffith M. (2001) A process map for consistent build conditions in the solid freeform fabrication of Thin – Walled Structure. J. Manuf. Sci. Eng., 123:615-622.  S.Natarajan, Dr.S.Muralidharan and N.L.Maharaja, “Investigation of Significance in Phase Transformation of Powder Metallurgy Steel Components During Heat Treatment- A Practicable Approach”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 2, 2013, pp. 189 - 195, ISSN Print: 0976-6340, ISSN Online: 0976-6359.  Iessa Sabbe Moosa, “Powder Metallurgy and its Application in the Production of Permanent Magnets”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 6, 2013, pp. 127 - 141, ISSN Print: 0976-6480, ISSN Online: 0976-6499.
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