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Journal of Materials Processing Technology 214 (2014) 1102– 1110

Contents lists available at ScienceDirect

Journal of Materials Processing Technology

jou rn al h om epage : www.elsev ier .com/ locate / jmatprotec

evelopment of micro-plasma transferred arc (�-PTA) wireeposition process for additive layer manufacturing applications

uyog Jhavara, N.K. Jaina,∗, C.P. Paulb

Discipline of Mechanical Engineering, Indian Institute of Technology Indore, MP, IndiaLaser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore, MP, India

r t i c l e i n f o

rticle history:eceived 18 October 2013eceived in revised form3 December 2013ccepted 26 December 2013vailable online 7 January 2014

eywords:icro-plasmaire deposition

dditive layer manufacturingepairingemanufacturingies and molds

a b s t r a c t

Micro-plasma transferred arc (�-PTA) deposition process has potential to meet requirements of themeso-sized fabrication and repair of the high value components. This paper reports on the developmentof �-PTA as cost effective and energy efficient alternative process for small sized deposition with anoverall objective to repair and/or remanufacture the defective dies and molds. An experimental setupwas developed to deposit 300 �m diameter wire of AISI P20 tool steel on the substrate of the same mate-rial which is one of the most commonly used materials for making the dies and molds used for variousapplications. Two stage experiments were conducted to indentify the important process parameters gen-erating regular and smooth single bead geometry. The process was further explored for highest possibledeposition rate for fabrication of straight walls through multi-layer deposition. The �-PTA depositionprocess was found to be capable of fabricating straight walls having total wall width of 2.45 mm andeffective wall width of 2.11 mm. The deposition efficiency was found to be 87% for the maximum depo-sition rate of 42 g/h. The microscopic examination and micro-hardness measurements revealed that the

deposited wall is free from cracks, porosity, and inclusions. This study confirms the capability of �-PTA forALM in comparison to the existing high energy deposition processes used for meso-scale fabrication andrepair applications of the dies and molds. This work confirms that �-PTA wire deposition process offersthe advantages of the laser based processes at much lower cost and more energy efficiency thus makingit potential alternative process for repair and remanufacturing of the defective dies and molds. Use offiner wire can further reduce the deposition size enabling �-PTA wire deposition process to fabricate the miniaturized parts.

. Introduction

Production of parts using additive layer manufacturing (ALM) isonsidered to be superior to the subtractive (i.e. various machin-ng processes) and deformative (i.e. various forming processes)

anufacturing processes due to its material and energy efficiency.LM can be used to fabricate near net-shape parts made of metals,olymers, ceramics, composites and functionally graded materials.evy et al. (2003) reviewed the ALM processes (both patented asell as commercialized) for rapid manufacturing and rapid tool-

ng applications and concluded that though technology of ALMor polymer based materials has matured with commercial avail-

bility of many rapid prototyping (RP) machines but, same is notrue for metallic materials and it still remains a challenge to theesearchers. They also mentioned that the type of energy sources one of the major factors differentiating among various ALM

∗ Corresponding author. Tel.: +91 732 4240 702; fax: +91 732 4240 761.E-mail address: nkjain@iiti.ac.in (N.K. Jain).

924-0136/$ – see front matter © 2014 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.jmatprotec.2013.12.016

© 2014 Elsevier B.V. All rights reserved.

processes. For metallic materials, laser, electron beam and elec-tric arc are major energy sources used in ALM. Laser and electronbeam are more precise energy sources than the electric arc there-fore they are more preferred for miniature sized deposition. But, amajor drawback is their poor energy conversion efficiency whichcauses higher energy consumption for fabrication of components,tooling and related applications. Use of energy efficient sourcesand increase in the deposition rates are the two major issues forALM processes. Suryakumar et al. (2011) have mentioned that thedeposition rate achieved by laser or electron beam is of the orderof 2–10 g/min whereas, electric arc based deposition processescan achieve it in the range of 50–130 g/min. Therefore, arc baseddeposition techniques are preferred for bulk deposition of metallicmaterials. Jandric et al. (2004) successfully built 3D-metallic partsusing gas tungsten arc welding (GTAW) process for depositing the

material. The manufactured part was free from cracks, porosity andhad uniform microstructure throughout. Akula and Karunakaran(2006) developed a direct metal rapid tool making process usingmetal inert gas (MIG) and metal active gas (MAG) welding inte-grated with computer numerical controlled (CNC) milling process

essing Technology 214 (2014) 1102– 1110 1103

tsa(s(fotmddbGhcdcsdmh

AdpbcsoKcaoscoul

dcssJmedsoaUrtntr

fTpcdots

Table 1Chemical composition of substrate and deposited material.

the body of the torch and the copper nozzle through charging ofplasma gas flowing between them. This arc was transferred to theworkpiece through an additional circuit provided between plasmanozzle and the substrate. The intense heat produced throughplasma causes melting and fusion of filler wire along with little

S. Jhavar et al. / Journal of Materials Proc

o manufacture the metallic dies and molds. Micro-arc based depo-ition is one of the recent ALM techniques having prospectivepplications in repairs and fabrication at meso-scale. Horii et al.2009) reported success in making 3D-structures using micro-ized wire for miniature deposition using micro-tungsten inert gas�-TIG) welding system. They mentioned that this can be usefulor meso-scale net-shaping. Almeida and Williams (2010) devel-ped out-of-chamber ALM using gas metal arc welding (GMAW)o deposit a wall of Ti-6Al-4V. Baufeld et al. (2011) deposited

ulti-layered single bead wall using a combination of laser beameposition and GTAW with the help of a 6-axis robotic system. Theyid comparative study of the mechanical properties of the depositsy both the processes. Their results confirm that both laser andTAW processes can be used for ALM applications. Few researchersave explored use of energy efficient processes for ALM appli-ations. Rangesh and O’Neill (2012) developed a free space metaleposition system using a lead-free soldering iron for ALM appli-ations. They used soldering arm as the heat source as well as aupport for the deposition. Martina et al. (2012) used plasma wireeposition to make walls of Ti-6Al-4V. They designed their experi-ents using D-optimal design method and achieved 1.8 kg/h as the

ighest deposition rate feeding 1.2 mm diameter wire at 100 mm/s.Form of the filler material is an important parameter in the

LM processes. It can be in the form of wire, micron-sized pow-er or combination of both. Paul et al. (2012) have mentioned thatowdered form of deposition material is preferred for the laserased processes. Whereas, wire form is preferred for fabrication ofomponents involving continuous deposition because intermittenttart and stop results in discontinuity in the deposited material. Usef wire also results in almost 100% material utilization efficiency.ukreja et al. (2012) have shown that the material utilization effi-iency in case of powdered filler material depends on the catchmentrea of the energy source. Powdered filler materials which fall outf the catchment area are often required to be recycled for rea-ons of cost effectiveness and environment friendliness. But, theirontamination hinders their recycling process. Moreover, storagef powdered filler material is also very challenging. Consequently,se of filler material in the form of wire is preferable because it is

ess complex, environment friendly and minimizes health hazards.Various defects in the dies and molds such as plastically

eformed geometries, minor cracks, deteriorated edges, heathecks, dents are mainly developed due to local impacts, thermaltresses and corrosion. If these defects can be identified at earlytage then they can be corrected through small sized deposition.havar et al. (2013) reviewed the various failure modes of dies and

olds and their repairing options and concluded that use of energyfficient ALM process to repair and/or remanufacture the defectiveies and molds can significantly improve their performance, lifepan and profitability. Rao (2012) in her survey on global scenariof dies and molds producers has concluded that the majority of diesnd molds producers are small and medium enterprises (SMEs).se of high energy beam processes (i.e. laser and electron beam) to

emanufacture/repair the defective dies and molds are limited dueo very high initial investment and higher operating cost which can-ot be afforded by SMEs. Therefore, there is an impending demando develop a low cost, material and energy efficient process forepair and remanufacturing of the defective dies and molds.

The present work attempts to develop micro-plasma trans-erred arc (�-PTA) wire deposition process to meet this demand.he paper reports a systematic study to indentify the optimumrocess parameters and characterizing its performance at various

ombinations of the input parameters. An experimental setup waseveloped to deposit AISI P20 tool steel wire of 300 �m diametern the substrate of the same material. Experiments were conductedo indentify the process parameters for producing regular andmooth single bead geometry. The process was further explored

Elements C Mn Cr Mo Si Cu Ni

Substrate 0.40 1.5 1.9 0.2 0.1 – –Deposited wire 0.1 0.97 1.9 1.03 0.54 0.03 0.03

for highest possible deposition rate to fabricate multi-layer straightwalls.

2. Experimentation

2.1. Material

In the present study, pre-hardened AISI P-20 tool steel samplesof size 100 mm × 180 mm × 9 mm were used as substrate. AISI P20tool steel is chromium–molybdenum steel, which can withstandthe forces encountered in the zinc die casting and plastic mold-ing. Chromium provides resistance to the oxidizing environment.Molybdenum helps it to resist pitting, crevice corrosion and resis-tance to non-oxidizing environment. This tool steel can be polishedto extremely high surface finish hence it is best suited for extrusiondies, press-brake dies, casting dies for aluminum, injection molds,medium and large size molds, and forming tools. The substrate sam-ples were cut, machined, shot blasted and cleaned with acetonebefore using for deposition (Table 1).

2.2. Experimental setup

Fig. 1 depicts the schematic of the experimental setup devel-oped for �-PTA deposition process. It was developed by integratingmicro-plasma welding system and an indigenously developed wirefeeding system with an X-Y worktable on which the substrate wasmounted. The spool of AISI P20 wire was loaded on the wire-feeding system which can feed the wire at rate of 850, 1275 and1700 mm/min. The nozzle of micro-plasma welding system wassuitably modified for feeding the wire to the melt-pool. Argongas was used for both plasma generation and shielding. An arcwas established between the tungsten electrode positioned within

Fig. 1. Schematic of the experimental setup developed for �-PTA deposition pro-cess.

1104 S. Jhavar et al. / Journal of Materials Processing Technology 214 (2014) 1102– 1110

Table 2Ranges (values) of the input parameters used in the pilot (main) experiments.

Parameter name Range for the pilot experiments Values for the main experiments

Plasma power (W) 50–450 350, 400, 450Travel speed of worktable (mm/min) 40–160 40, 50, 63, 80, 100Wire feed rate (mm/min) 850–1700 850, 1275, 1700Wire feed angle (degrees) 20–60 45Stand-off distance (mm) 5–8 5

matvtY

2

pwnrwsrw

ttemtp(acotflattdpd

pits3wste3ofwtdi

Plasma gas flow rate (nl/min) 0.1–0.5

Shield gas flow rate (nl/min) 3.0–8.0

elting of the substrate. The melt pool was protected by providingn envelope of the shielding gas throughout the process. This sys-em had maximum plasma power capacity of 450 W with currentarying in the range of 0.1–18 A with a step of 0.1 A. The work-able had travel length of 300 mm in X-direction, 160 mm in the-direction and a maximum travel speed of 100 mm/min.

.3. Experimental procedure and observations

The experiments were planned and conducted in two stages: (a)ilot experiments and (b) main experiments. The pilot experimentsere conducted (i) to bracket the ranges of three input parametersamely plasma power (P), travel speed of worktable (v), wire feedate (f) for the main experiments, and (ii) to find optimum value ofire feed angle, stand-off distance (SOD), plasma gas flow rate and

hield gas flow rate for main experiments. Table 2 mentions theanges of the input parameters used in the pilot experiments alongith the ranges or values identified for the main experiments.

During the pilot experiments, wire feed angle of 45◦ was foundo produce the highest deposition efficiency with front feeding ofhe wire and same is also confirmed by previous work by Abioyet al. (2013). Stand-off distance of 5 mm was found to be opti-um as it allowed smooth wire feeding to the melt zone through

he wire feed nozzle while, higher stand-off distance decreasedlasma power. This matches with the conclusions of Wang et al.2003) who studied the variation in the plasma power with SODnd plasma current and found that the maximum plasma poweran be obtained at SOD between 4 and 6 mm. Plasma gas flow ratef 0.4 normal liter per minute (nl/min) was found to be sufficiento transfer plasma power toward the substrate while, shield gasow rate of 5 nl/min was found sufficient to protect melt pool fromtmospheric contamination. It was observed that lower values ofhe shield gas flow rate allowed the atmospheric gases to react withhe melt pool resulting in porous and uneven deposition and spatteruring deposition whereas, higher values caused spread of moltenool generating dimple like impression over the top surface of theeposit.

Based on the pilot experiments, three parameters namelylasma power, travel speed of worktable and wire feed rate were

dentified as most significant parameters for the further studies inhe main experiments for depositing single track over AISI P20 toolteel. It was observed during the pilot experiments that a minimum00 W of plasma power was required to melt the stationary AISI P20ire of 300 �m. A small portion of heat is also required to melt the

ubstrate during �-PTA deposition called wetting which is requiredo develop strong bond between the substrate and consecutive lay-rs. Therefore, plasma power was bracketed to vary in the range of50–450 W for the main experiments. Discontinuous tracks werebserved for the travel speed of worktable more than 100 mm/min

or the maximum wire feed rate. Hence, a range of 40–100 mm/minas bracketed for travel speed of the worktable. All three values of

he wire feed rate available with the fabricated system were useduring the main experiments. Consequently, forty five main exper-

ments were planned and conducted using full factorial approach

0.45.0

to study the effects of plasma power, travel speed of the worktable,and wire feed rate on the width, height and quality of the singlebead deposited track. Each experiment was repeated thrice and thebest result in terms of bead quality for each experiment is reportedin this paper. Table 3 presents the values of the input parametersand corresponding responses for main experiments.

Each deposited track was cut in the direction transverse to thedeposition direction and the sample was prepared using standardmetallographic procedure for optical microscopy. Leica DM IL com-pact inverted microscope was used to measure the height andwidth of the deposited track. The quality of each deposition trackwas determined through visual examination. Based on the depo-sition quality, selected tracks were further analyzed to evaluateenergy input per unit traverse length ‘El’ in J/mm, volumetric feedrate of wire per unit traverse length ‘Vl’ in mm3/mm and materialdeposition rate ‘G’ in g/h. The combination of the process param-eters that deposited the track with the lowest energy input perunit traverse length and highest deposition rate was selected formulti-layer deposition to fabricate straight walls. The cross-sectionof deposited wall was analyzed with the help of AutoCAD softwareto calculate surface waviness and deposition efficiency. Scanningelectron microscopy (SEM) was done on Zeiss supra 55 to examinepresence of any porosity, inclusion and cracks in the multi-layerdeposition. The micro-hardness was measured using UHL VMHTapplying a load of 500 gf for the duration of 15 s.

3. Results and analysis

It was observed during the experiments that use of higher valuesof plasma power and lower wire feed rate caused over-melting ofthe base and filler material and even evaporation of the depositedmaterial which led to discontinuity, cavities and either no or verylitter deposition. On the contrary, use of lower plasma power andhigher wire feed rate resulted in lower bonding between the sub-strate and the filler material due to insufficient melting of the fillermaterial and its collision with the substrate in the extreme case. Thecollision produced during deposition may deflect delivery of thefiller wire offsetting it from the center position. As wire position-ing to plasma delivery center is very important in order to utilizethe maximum plasma energy and produce sound deposition, centeroffsetting may cause wrong wire positioning and irregular deposits.It was noted that there is a balance of plasma power and wire feedrate required for the sound deposition.

From the experimental results presented in Table 3, those ninecombinations of input parameters (corresponding to the exp. no.12, 13, 14, 27, 28, 29, 38, 39 and 40) producing regular and smoothsingle track geometry were identified for further investigations. Itcan be observed that the values of the width and height of depositedtrack for these parametric combinations ranges from 1.3 to 2 mm

and 0.6 to 1 mm respectively.

Fig. 2 depicts optical micro-graphs for these nine samples. Thegeometry of the track deposited by �-PTA depends on the inter-action of micro-plasma (i.e. heat source) and the type of materialbeing deposited. Two parameters namely plasma energy per unit

S. Jhavar et al. / Journal of Materials Processing Technology 214 (2014) 1102– 1110 1105

Table 3Values of variable input parameters and corresponding responses for the main experiments.

Exp. no. Variable input parameters Responses

Plasma power‘P’ (W)

Travel speed of worktable‘v’ (mm/min)

Wire feed rate‘f’ (mm/min)

Deposited trackwidth (mm)

Deposited trackheight (mm)

Quality of deposition

1 350 40 1700 1.9 1.8 Non-uniform deposit2 350 50 1700 1.8 1.6 Non-uniform deposit3 350 63 1700 1.5 1.3 Non-uniform deposit4 350 80 1700 1.4 1.2 Non-uniform deposit5 350 100 1700 1.2 1 Non-uniform deposit6 350 40 1275 1.6 1.4 Non-uniform deposit7 350 50 1275 1.5 1.3 Non-uniform deposit8 350 63 1275 1.4 1.2 Non-uniform deposit9 350 80 1275 1.2 1 Non-uniform deposit10 350 100 1275 1.1 0.8 Non-uniform deposit11 350 40 850 1.5 1.2 Non-uniform deposit12 350 50 850 1.3 1 Regular deposit13 350 63 850 1.3 0.8 Regular deposit14 350 80 850 1.4 0.7 Regular deposit15 350 100 850 1.5 0.6 Non-uniform deposit16 400 40 1700 2 1.6 Non-uniform deposit17 400 50 1700 2 1.4 Non-uniform deposit18 400 63 1700 1.9 1.1 Non-uniform deposit19 400 80 1700 1.8 0.9 Non-uniform deposit20 400 100 1700 1.9 0.8 Non-uniform deposit21 400 40 1275 1.9 1.4 Non-uniform deposit22 400 50 1275 1.8 1.2 Non-uniform deposit23 400 63 1275 1.8 1 Non-uniform deposit24 400 80 1275 1.9 0.9 Non-uniform deposit25 400 100 1275 2 0.8 Non-uniform deposit26 400 40 850 1.8 0.9 Non-uniform deposit27 400 50 850 1.7 0.8 Regular deposit28 400 63 850 1.6 0.7 Regular deposit29 400 80 850 1.8 0.6 Regular deposit30 400 100 850 1.9 0.5 Non-uniform deposit31 450 40 1700 2.1 1.5 Non-uniform deposit32 450 50 1700 2.1 1.3 Non-uniform deposit33 450 63 1700 2 1 Non-uniform deposit34 450 80 1700 1.9 0.9 Non-uniform deposit35 450 100 1700 2.1 0.8 Non-uniform deposit36 450 40 1275 2.2 1.3 Non-uniform deposit37 450 50 1275 2.1 1.1 Non-uniform deposit38 450 63 1275 1.9 0.9 Regular deposit39 450 80 1275 1.7 0.7 Regular deposit40 450 100 1275 2 0.6 Regular deposit41 450 40 850 1.9 0.9 Non-uniform deposit

tefmlTpo

TI

42 450 50 850

43 450 63 850

44 450 80 850

45 450 100 850

raverse length (El) and volumetric feed rate of wire per unit trav-rse length (Vl) governs the consumption of plasma energy andeed material for a single track deposition thus determining the

aterial deposition rate (G). The three parameters were calcu-ated using equations (1a)–(1c). These calculations are shown inable 4. It can be observed from data that the threshold values oflasma energy per unit of traverse length and volumetric feed ratef wire per unit traverse length are 262 J/mm and 10.6 mm3/mm

able 4dentified experimental conditions giving the regular deposition.

Exp. no. Plasma power‘P’ (W)

Travel speed ofworktable ‘v’(mm/min)

Wire feed rate ‘f’(mm/min)

Plaun(J/m

12 350 50 850 4213 350 63 850 3314 350 80 850 2627 400 50 850 4828 400 63 850 3829 400 80 850 3038 450 63 1275 4239 450 80 1275 3340 450 100 1275 270

2.1 0.8 Non-uniform deposit1.8 0.6 Non-uniform deposit2 0.4 Non-uniform deposit0.6 0.1 Non-uniform deposit

respectively for the regular and smooth deposition yielding a depo-sition rate of 28.1 g/h.

60P

El (J/mm) =

V(1a)

Vl (mm3/mm) = Awf

v(1b)

sma energy input perit traverse length ‘El ’

m)

Volumetric feed rate ofwire per unit traverselength ‘Vl ’ (mm3/mm)

Material depositionrate ‘G’ (g/h)

0.00 17 28.13.33 13.49 28.12.50 10.63 28.10.00 17 28.10.95 13.49 28.10.00 10.63 28.18.57 20.24 42.27.50 15.94 42.2

.00 12.75 42.2

1106 S. Jhavar et al. / Journal of Materials Processing Technology 214 (2014) 1102– 1110

havin

G

Hd

Fig. 2. Optical micrographs of the nine samples

(g/h) = 60Awf�w (1c)

ere, Aw is the cross section area of the wire (mm2) and �w is theensity of the wire (g/mm3).

g regular and uniform single-bead deposition.

3.1. Characteristics of multi-layer deposits

Out of the nine parametric combinations, the one which gavethe lowest plasma energy input per unit traverse length and high-est deposition rate (i.e. experiment no. 40 in Table 4) was selected

S. Jhavar et al. / Journal of Materials Processing Technology 214 (2014) 1102– 1110 1107

and (b

fewspstgFattdwaisidga

awcwwrEl

Fig. 3. Typical multi-layer deposition (a) geometry

or multi-layer deposition of a straight wall consisting of 15 lay-rs with deposition length of 50 mm for each layer. The depositionas started from the end point of the previous layer for each sub-

equent layer. The experiment was repeated thrice to confirm therocess accuracy. The average values of deposition height mea-ured from the substrate were 7.6 mm, 8 mm and 7.8 mm for thehree fabricated multi-layer deposited straight walls. Fig. 3a showseometry of the best quality multi-layer deposited sample, whileig. 3b depicts the SEM images of deposition at various locationslong the height of straight wall. It can be seen from these figureshat the multi-layer deposition gave smooth but little wavy surfaceopography necessitating some finishing operation to achieve planeeposition surface. It also signifies the complete melting of fillerire during deposition and good bonding between the intermedi-

te layers. The samples were subjected to dye penetration tests andt was confirmed that the deposited samples were free from defectsuch as cracks, porosity and inclusions at the surface. From the SEMmages shown in Fig. 3b, it can be observed that the multi-layereposition has dense structure having uniform and non-dendriticrains at a particular location and is free from porosity, inclusionsnd cracks.

The deposited wall of the best multi-layer sample was furthernalyzed for calculating total wall width (TWW), effective wallidth (EWW) and deposition efficiency. For this, the wall was

ut in the transverse direction to deposition. The deposited walls

ere observed to be irregular over side surfaces due to inter-layeraviness and required subsequent finishing. Martina et al. (2012)

eferred wall width before and after the finishing as TWW andWW respectively. The sample was prepared using standard metal-ographic procedure for optical microscopy. The optical micrograph

) SEM images at various locations along its height.

image was processed in the AutoCAD software of Autodesk Inc. forthe calculation of TWW, EWW, surface waviness (Eq. (2)) and depo-sition efficiency (Eq. (3)). The AutoCAD post-processed micrographof the transverse section is shown in Fig. 4.

Surface waviness = Total wall width − Effective wall width2

(2)

Deposition efficiency = Area‘A’Area‘A’ + Area‘B’ + Area‘C’

(3)

Microscopy of the samples also confirmed that there was nointer-layer or trans-layer porosity in the samples and the depositswere smooth and have good bonding strength with the substrateand inter-layer deposits. The �-PTA deposition process was ableto fabricate straight wall having TWW of 2.45 mm and EWW of2.11 mm. The deposition efficiency was found to be 87% with a max-imum deposition rate of 42 g/h. The surface waviness was found tobe 0.17 mm.

3.2. Micro-hardness measurement

The micro-hardness of the �-PTA deposited material across thecross-section was measured. Fig. 5 shows values of the micro-hardness along the height of deposition.

A minimum hardness value of 253 HV was found near to the top

layer and a maximum hardness value of 616 HV in the HAZ. Lit-tle variation in micro-hardness was found within a particular layerwhereas, there is a significant variation across the deposited lay-ers. It can also be observed that the higher values of micro-hardnessoccur near the heat affected zone (HAZ) which spreads up to few

1108 S. Jhavar et al. / Journal of Materials Processing Technology 214 (2014) 1102– 1110

Fm

mqlatatihto

height (LH). It reveals that though plasma wire deposition (PWD)can achieve smaller size deposition than the gas metal arc welding

TC

ig. 4. Optical micrograph showing various parameters used to judge the quality ofulti-layer wall deposition by �-PTA process.

illimeters. The micro-hardness decreases slightly with subse-uent layers toward the top. This is due to the fact that the initial

ayers are deposited over a substrate at room temperature, whichcts as a heat sink giving relatively higher cooling rate as comparedo the subsequent layers for which the previous deposited layersct as heat sink. Higher carbon content of the substrate also con-ributes to higher hardness values near the substrate. The hardnessn the HAZ can be minimized using a preheated substrate or giving

eat treatment after the deposition. The deposition above few ini-ial layers were found almost harmonized and the hardness valuesf these zones were found near to that of the substrate.

able 5omparison of the outcome of the present work with some of the most recent experimen

Authors (year) Type of energysource

Filler materialand its form

Energy consumptiper unit traverse le(J/mm)

Bi and Gasser (2011) Nd:YAG laser Powder ofNi-based superalloy

36

Gharbi et al. (2013) Yb:YAG laser Powder ofTi-6Al-4V

48–75

Ravi et al. (2013) Disk laser Powder ofSC420

7.0–67.5

Zhao et al. (2012) GMAW 1.2 mmdiameter wireof H08Mn2Si

1490

Present work Micro-plasma 0.3 mmdiameter wireof AISI P-20steel

270

Fig. 5. Micro-hardness profile for the best quality multi-layer deposited sample.

3.3. Comparison with other competitive processes

Table 5 presents comparison of the results of present workwith some of the most recent experimental studies on multi-layerwall deposition using single bead geometry in terms of the energysource used, filler material and its form, energy consumption perunit traverse length (J/mm), consumption rate of the filler mate-rial, power consumption per unit filler material consumption andTWW. It can be observed from this comparison that though thelaser based deposition processes require very less energy inputper unit traverse length but their power consumption per unit offiller material consumption is very high. Moreover, they have poorenergy conversion efficiency. While, conventional arc based depo-sition processes require very high energy per unit traverse lengthand use high feed rate of the filler material but consume less powerper unit filler material consumption. They also focus higher amountof heat over larger area therefore it is difficult to use these pro-cesses for meso-scale deposition. It is evident from Table 5 that�-PTA wire deposition process is very economical and energy effi-cient because it requires much less power consumption per unitfiller material consumption as compared to the laser and arc basedprocesses. Fig. 6 compares the performance of the �-PTA deposi-tion process with the other competitive processes as reported byMartina et al. (2012) in terms of terms of TWW, EWW and layer

(GMAW) based processes it cannot achieve very small size deposi-tion which can be achieved by the laser based processes. It is alsoevident from the comparison of Fig. 6 that �-PTA wire deposition

tal studies on single bead multi-layer wall deposition.

onngth

Consumption rateof the fillermaterial

Power consumptionper unit filler materialconsumption

TWW

1.5 g/min 12,000 J/g 1.3 mm

1 g/min 19,200–30,000 J/g 1.9–2.1 mm

2.6–12 g/min 2304–9000 J/g 0.5–4.0 mm

2880 mm/min 50.4 J/mm N.A.

1275 mm/min 21.1 J/mm 2.45 mm

S. Jhavar et al. / Journal of Materials Processing Technology 214 (2014) 1102– 1110 1109

F tal wp

ppetmc

4

sauw

1

2

3

4

5

6

ig. 6. Comparison of �-PTA process with other deposition processes in terms of torocesses taken from Martina et al. (2012)].

rocess can bridge this gap and can fabricate the meso-scale com-onents. Use of finer wire can further reduce the deposition sizenabling �-PTA wire deposition process to fabricate the minia-urized parts and offer the capabilities of laser based processes at

uch lower cost and power consumption per unit filler materialonsumption.

. Conclusions

This paper reported on the development of �-PTA wire depo-ition process for various additive layered manufacturing (ALM)pplications involving meso-scale deposition for repair and reman-facturing. Following conclusion can be drawn from the presentork:

. The plasma energy per unit of traverse length and volumetricwire feed rate of wire per unit traverse length were found to havethreshold values of 262 J/mm and 10.6 mm3/mm respectively forthe regular and smooth deposition yielding a deposition rate of28.1 g/h.

. Multi-layer deposited geometry consisted of fully dense struc-ture of good surface quality.

. The deposition above few initial layers was found to be homoge-neous and the hardness values of these zones were found nearto that of the substrate.

. The �-PTA wire deposition process was able to fabricate straightwall consisting of 15 layers having TWW of 2.45 mm with anEWW of 2.11 mm with a deposition efficiency of 87% and couldachieve a maximum deposition rate of 42 g/h.

. �-PTA wire deposition process confirmed to be cost-effective,energy efficient and environmental friendly process for multi-layer deposition and has potential to become alternative processfor repairing and remanufacturing of the defective dies andmolds and other high value engineering components.

. The present study used 300 �m diameter wire but it can be fur-

ther extended using smaller wire size for the finer deposition andusing variety of the filler and substrate materials and to charac-terize the deposition. Use of finer wire can further reduce thedeposition size enabling �-PTA wire deposition process to fab-ricate the miniaturized parts and offer the capabilities of laser

all width (TWW), effective wall width (EWW) and layer height (LH) [data for other

based processes at much lower cost and power consumption perunit consumption of the filler material.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.jmatprotec.2013.12.016.

References

Abioye, T.E., Folkes, J., Clare, A.T., 2013. A parametric study of Inconel 625wire laser deposition. Journal of Materials Processing Technology 212,203–210.

Akula, S., Karunakaran, K.P., 2006. Hybrid adaptive layer manufacturing: an intelli-gent art of direct metal rapid tooling process. Robotics and Computer-IntegratedManufacturing 22, 113–123.

Almeida, P.M.S., Williams, S., 2010. Innovative process model of Ti-6Al-4V addi-tive layer manufacturing using cold metal transfer (CMT). In: Proceedingsof the 21st Annual International Solid Freeform Fabrication Symposium,pp. 25–36.

Baufeld, B., Brandl, E., Biest, O.V.D., 2011. Wire based additive layer manufacturing:comparison of microstructure and mechanical properties of Ti–6Al–4V compo-nents fabricated by laser-beam deposition and shaped metal deposition. Journalof Materials Processing Technology 211, 1146–1158.

Bi, G., Gasser, A., 2011. Restoration of nickel-base turbine blade knife-edgeswith controlled laser aided additive manufacturing. Physics Procedia 12,402–409.

Gharbi, M., Peyre, P., Gorny, C., Carin, M., Morville, S., Masson, P.L., Carron, D., Fabbro,R., 2013. Influence of various process conditions on surface finishes inducedby the direct metal deposition laser technique on a Ti–6Al–4V alloy. Journal ofMaterials Processing Technology 213, 791–800.

Horii, T., Kirihara, S., Miyamoto, Y., 2009. Freeform fabrication of superalloy objectsby 3D micro welding. Materials & Design 30, 1093–1097.

Jandric, Z., Labudovic, M., Kovacevic, R., 2004. Effect of heat sink on microstruc-ture of three-dimensional parts built by welding-based deposition. InternationalJournal of Machine Tools & Manufacture 44, 785–796.

Jhavar, S., Paul, C.P., Jain, N.K., 2013. Causes of failure and repairing optionsfor dies and molds: a review. Engineering Failure Analysis 34, 519–535,http://dx.doi.org/10.1016/j.engfailanal.2013.09.006.

Kukreja, L.M., Kaul, R., Paul, C.P., Ganesh, P., Rao, B.T., 2012. Emerging laser mate-rials processing techniques for future industrial applications. In: Manna, I.,

Majumder, J. (Eds.), Laser Assisted Fabrication of Materials. Springer-Verlag,Berlin, pp. 423–478.

Levy, G.N., Schindel, R., Kruth, J.P., 2003. Rapid manufacturing and rapidtooling with layer manufacturing (LM) technologies: state of the artand future perspectives. CIRP Annals – Manufacturing Technology 52 (2),589–609.

1 cessing

M

P

R

R

110 S. Jhavar et al. / Journal of Materials Pro

artina, F., Mehnen, J., Williams, S.W., Colegrove, P., Wang, F., 2012. Inves-tigation of the benefits of plasma deposition for the additive layermanufacture of Ti–6Al–4V. Journal of Materials Processing Technology 212,1377–1386.

aul, C.P., Bhargava, P., Kumar, A., Pathak, A.K., Kukreja, L.M., 2012. Laserrapid manufacturing: technology, applications, modeling and futureprospects. In: Davim, J.P. (Ed.), Lasers in Manufacturing. Wiley-ISTE, London,

pp. 1–67.

angesh, A., O’Neill, W., 2012. The foundations of a new approach to additive man-ufacturing: characteristics of free space metal deposition. Journal of MaterialsProcessing Technology 212, 203–210.

ao, I., 2012. Casting Dies for a Sustainable Future. Efficient Manufacturing, India,pp. 26–28.

Technology 214 (2014) 1102– 1110

Ravi, G.A., Hao, X.J., Wain, N., Wu, X., Attallah, M.M., 2013. Direct laser fabrication ofthree dimensional components using SC420 stainless steel. Materials and Design47, 731–736.

Suryakumar, S., Karunakaran, K.P., Bernard, A., Chandrasekhar, U., Raghavender,N., Sharma, D., 2011. Weld bead modeling and process optimiza-tion in hybrid layered manufacturing. Computer-Aided Design 43,331–344.

Wang, H., Jiang, W., Valant, M., Kovacevic, R., 2003. Microplasma powder depositionas a new solid freeform fabrication process. Proceedings of the Institution ofMechanical Engineers 217, 1641–1650.

Zhao, H., Zhang, G., Yin, Z., Wu, L., 2012. Three-dimensional finite element analysis ofthermal stress in single-pass multi-layer weld-based rapid prototyping. Journalof Materials Processing Technology 212, 276–285.