EFFECT OF PLASMA SPRAY NANO COMPOSITE COATING ON … · 2020. 8. 27. · N PPM 50 100 1.1 Coating Materials Preparation: In the plasma spraying process, particles of Al 2O 3:13%TiO

International Journal of Engineering Technology, Management and Applied Sciences

www.ijetmas.com September 2014, Volume 2 Issue 4, ISSN 2349-4476

1 P.Vijayanand, Amitesh kumar, K.R.Vijayakumar , K RameshBabu

EFFECT OF PLASMA SPRAY

NANO COMPOSITE COATING ON MILD STEEL

P.Vijayanand1

Amitesh kumar2

K.R.Vijaya kumar3

Research scholar, Ranchi University, Assistant. Professor, NIFFT Professor, Dr.MGR.ERIU

Md.Nazir Hussain

4 P.Kumaran

5 K RameshBabu

6

Associate Professor, CIT, Associate Professor, Saveetha University Professor & HOD, ADCET, S.U.

ABSTRACT

The development of nanotechnology enables to reinforce or improve the metallurgical and mechanical properties of

the deposited layer. In this work, coating of mild steel using the nano Composite material of Al2O3 with 13%TiO2 &

0.2%Graphene will be carried out and metallurgical and morphological changes in the resulting coating will be

examined. The coating is produced by different processes, which are the Plasma spray coating, wire arc, HVOF etc.

In this review is based on characterization of plasma sprayed nano structured coatings on Mild steel. By adding nano

particles, the properties are investigated like hardness, wear resistance etc. Consequently, investigation of the

resulting coating properties becomes essential. The objective of the present study is to investigate the metallurgical

and morphological changes in the coatings produced by plasma spraying process using nano powders.

Keywords

Al2O3:13% TiO2coating, Graphene microstructure, plasma spraying process.

1. INTRODUCTION

A coating is produced by a process in which molten or softened particles are applied by impact

onto a substrate. A common feature of all thermal spray coatings is their lenticular or lamellar

grain structure resulting from the rapid solidification of small globules, flattened from striking a

cold surface at high velocities. Figure 1 shows schematic sketch of thermal spray process.

Thermal Spraying is a technique of coating manufacturing implementing a wide variety of

processes and materials. Atmospheric plasma spraying (APS) is one of these processes based on

the creation of a plasma jet to melt a feedstock powder. Powder particles are injected with the aid

of a carrier gas; they gain their velocity and temperature by thermal and momentum transfers

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from the plasma jet. At the surface of the substrate, particles flatten and solidify rapidly forming

a stack of lamellae. Micro-cracks appear also in the microstructure as a consequence of stress

Accommodation due to the high spray temperature and a large difference in thermal dilation

coefficients between the substrate and coating. This is mainly the case for ceramic coatings

deposited on metallic substrates (3).

Fig 1: Thermal spray coating process

Thermal spray techniques such as plasma spray, molten and accelerated toward a substrate where

it impacts creating a coating are widely used in industry (4)

Plasma sprayed ceramic coatings, for their higher strength-to-weight ratio and superior wear-

resistant properties, are preferred in most tribological applications. The suitability of a ceramic

coating on metal substrates depends on (a) the adherence strength at coating–substrate interface

and (b) stability at operating conditions. Critical components in high-tech industries operate

under extremely hostile conditions of temperature, gas flow, heat flux, and corrosive media,

which severely limit their service life. This problem can be overcome by using composite





Structures consisting of the core material with a suitable surface coating. Plasma spray

technology, the process of preparing overlay coating on any surface, is one of the most widely

used techniques to prepare such composite structural parts with improved properties and

increased life span. Composite coatings are defined as the deposits produced by thermal spraying

containing at least two distinctive, intentionally present phases apart from porosity.

In plasma arc spray, an electric arc is used to indirectly melt the coating material by creating a

plasma flame. The plasma flame is achieved by ionizing a plasma gas mixture such as argon,

nitrogen, helium or hydrogen. The inert gas temperature must be increased to elevated levels, to

reach the ionization state of the gas. As a result, an electric arc, this has a temperature in

excess of 5,000oK, is used and maintained along with the constant flow of the inert gas to

maintain the plasma flame. Using plasma as a heat source, it is possible to thermally spray a

wide range of materials that is not limited to polymers and metals only, but also extended to high

melting temperature materials such as ceramics. The coating material is generally in the powder

form. Commercial agglomerated nano powders are now avail- able. However, the process must

be carefully controlled in order to keep the initial nanostructure in the final coating (6).

Fig 2: Plasma spray process





The Plasma Spray Process is basically the spraying of molten or heat softened material onto a

surface to provide a coating. Material in the form of powder is injected into a very high

temperature plasma flame, where it is rapidly heated and accelerated to a high velocity. The hot

material impacts on the substrate surface and rapidly cools forming a coating.

Plasma spraying of nano sized powder is a well-established process in this decade (2).Below

composition of HR Plate of IS2062 can be used as Substrate.

Table 1: Chemical Composition & Mechanical Composition for IS2062 HR Plate

Chemical

Composition percentage Range

Carbon 0.14 0.23Max

Manganese 0.81 1.5Max

Sulphur 0.021 0.045Max

Phosphorous 0.025 0.045Max

Aluminum 0.027 0.02Min

Silicon 0.109 0.4Max

C equivalent 0.275 0.42Max

YS 355 255Min

UTS 458 410Min

Elongation 34 23Min

Bend ok

N PPM 50 100

1.1 Coating Materials Preparation:

In the plasma spraying process, particles of Al2O3:13%TiO2 and graphene powder are injected

into plasma jet and are rapidly melted and accelerated to produce stream of molten particles that

are spray onto the substrate Mild steel plate(40mmx80mmx4mm).

And using Graphene nano sized powders feedstock to generate nano structured coatings presents

new challenges as well as new opportunities. The typical spraying parameters for

Al2O3:13%TiO2also carried out of similar substrate used. Graphene powder of 0.2% added in the

Al2O3:13%TiO2. The thickness of the Graphene powder is 5nm. The purity of Carbon in the

graphene is 99%.





1.2 Plasma spraying parameters:

This is a typical plasma spray system operating in the non-transferred mode. The major

components of this set-up include the plasma torch, power supply, power feeder, plasma gas

supply, control console, cooling water, and the spray booth. Prior to spraying, the substrates are

grit blasted by compressed air at a pressure of 3 kgf/cm2.Acurrent regulated DC power supply is

used. A four stage closed loop centrifugal pump at a pressure of 10 kgf/cm2 supplies cooling

water for the system.

The primary plasma gas (argon) and the secondary gas (hydrogen) are taken from normal

cylinders at an outlet pressure of 4kgf/cm2. The plasma torch input power is varied from 11 to

21kW by controlling the gas flow rate, plasma arc current, and the arc voltage. The powder feed

rate is kept constant at about 11.5 g/min by a turntable type volumetric powder feeder. Operating

parameters used during the spraying are given in Table 2

Table 2: Operating parameters used during the plasma Spraying process.

Parameters used

in the SutzlerMetco USA

Range

Spray Torch 9MB

Operating Power 11-21KW

Current 500A

Voltage 65-70V

Plasma gas (Ar) flow rate 100psi

Secondary gas (H2) flow rate 15psi

Powder feed rate 11.5gm/min

Spray Distance 13”

Pre-work Grit Blasting





2. RESULT & DISCUSSION:

2.1 Hardness of the coatings: Vickers micro hardness measurements were performed under a 0.5Kg load

for 15s on the cross-sections of the coatings. A total of 6 micro hardness measurements were carried out for each

coating. The mean micro hardness of both coating is about 3200& 1400. The observed hardness difference is

believed to result partially from different coating due to grapheme powder affects the coating hardness.

Fig 3: Vickers Micro hardness Machine Table 3: Vickers Micro hardness

2.2 Adhesive test: Tap Test method as per ASTM D3359.

On metal substrates, a more formal version of the knife test is the tape test. Pressure sensitive

tape is applied and removed over cuts made in the coating. There are two variants of this test; the

X-cut tape test and the cross hatch tape test.

The X-cut tape test is primarily intended for use at job sites. Using a sharp razor blade, scalpel,

knife or other cutting device, two cuts are made into the coating with a 30o – 45

o angle between

legs and down to the substrate which intersects to form an “X”. A steel or other hard metal

S.

no

Al2O3+TiO2

H.V @ 0.5 Kg

Load :Dwell:

10s

Al2O3+TiO2+Graphene 0.2%

H.V @ 0.5 Kg Load :Dwell: 10s

1

3197.0

1391.0

2

210.0

1395.0

3

3194.0

1411.0

4

3220.0

1413.0

5

3194.0

1395.0

6

3220.0

14130





Straight edge is used to ensure straight cuts. Tape is placed on the center of the intersection of

the cuts and then removed rapidly. The X-cut area is then inspected for removal of coating from

the substrate or previous coating and rated.

The cross hatch tape test is primarily intended for use in the laboratory on coatings less than 5

miles (125 microns) thick. It uses a cross-hatch pattern rather than the X pattern. A cutting guide

or a special cross-hatch cutter with multiple preset blades is needed to make sure the incisions

are properly spaced and parallel. After the tape has been applied and pulled off, the cut area is

then inspected and rated.

Fig 4.1-Al2O3:13%TiO2 (before) Fig 5.1 -Al2O3:13%TiO2:0.2%Graphene (before)

Fig 4.2 -Al2O3:13%TiO2 (After) Fig 5.2 - Al2O3:13%TiO2: 0.2%Graphene (After)





Fig6-Pasting tape on Substrate Fig 7- Peel-Off tape from Substrate

Sharp 450 hatched lines made at equidistance with the help of sharp H.S.S. tool bit on the

surfaces of Al2O3 : 13%TiO2(Fig 4.1 &4.2) & Al2O3 : 13%TiO2:0.2%Graphene( Fig 5.1, 5.2)The

image shows the hatched surface after the peel off test is conducted(Fig7). The complete squares

are intact and no coating has been removed from the coated surface of the Al2O3:13%TiO2 &

Al2O3:13%TiO2: 0.2%Graphene.Both the coated has good adhesive strength.

A rough surface provides a good coating adhesion. A rough surface provides enough room for

anchorage of the splats facilitating bonding through mechanical interlocking (3).

2.3 Coating Characterization:

EDX analysis was performed to determine the atomic composition of the different phases found

in the coatings of Al2O3:13%TiO2 & Al2O3:13%TiO2: 0.2% Graphene. Coatings are confirmed to

be formed by melted matrix particles of TiO2& Graphene.





Fig 8 EDX Analysis of nano structured Al2O3: 13%TiO2

Fig 9 EDX Analysis of Nano structured Al2O3 : 13%TiO2: 0.2%Graphene

2.4 Coating Micro Structure:

The Cross section of the coatings was studied with FESEM. The coatings Al2O3:13%TiO2

relatively denser compared to their Al2O3:TiO2:0.2%Graphene due to oxidation effect. Oxidation

of metals and alloys took place when they are heated to elevated temperatures in air or highly

oxidizing environment (14).





Fig 10. SEM analysis of Al2O3 :13%TiO2 coated surface of SubstrateAl2O3 : 13%TiO2: 0.2% Graphene

Fig 11 .SEM analysis of Al2O3:13%TiO2 coated surface of Substrate





3. RESULTS:

I. Effects of Plasma sprayed coatings have different composition with different parameters

analyzed.

II. Determination of mechanical properties like hardness, Adhesive in the coated mild steel

plates.

III. Addition of Graphene powder in the Al2O3:13%TiO2 have shown lesser Micro hardness &

can be used in the application of bending work.

IV. If uniformly deposited, shows improved properties like more surface adhesive &Micro

hardness.

V. Mild steel substrate of Hot rolled materials (IS2062) have analyzed by adhesive, hardness

test.

VI. If graphene content increases, electrical conductivity & Thermal conductivity also increases.

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EFFECT OF PLASMA SPRAY NANO COMPOSITE COATING ON … · 2020. 8. 27. · N PPM 50 100 1.1 Coating Materials Preparation: In the plasma spraying process, particles of Al 2O 3:13%TiO