parametric study of abrasive wear of co crc based flame sprayed coatings by response surface...

8/11/2019 Parametric Study of Abrasive Wear of Co CrC Based Flame Sprayed Coatings by Response Surface Methodology

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Author's Accepted Manuscript

Parametric study of abrasive wear of Co-CrCbased flame sprayed coatings by Response

Surface Methodology

Satpal Sharma

PII: S0301-679X(14)00091-7DOI: http://dx.doi.org/10.1016/j.triboint.2014.03.004

Reference: JTRI3274

To appear in: Tribology International

Received date: 14 January 2014Accepted date: 4 March 2014

Cite this article as: Satpal Sharma, Parametric study of abrasive wear of Co-CrCbased flame sprayed coatings by Response Surface Methodology, TribologyInternational, http://dx.doi.org/10.1016/j.triboint.2014.03.004

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Parametric study of abrasive wear of Co-CrC based flame sprayed coatings by

Response Surface Methodology

Satpal Sharma

School of Engineering, Gautam Buddha University, Greater Noida, U.P. (India)

[email protected]

Abstract

Co base powder (EWAC1006 EE) was modified with the addition of 20%WC and the same was

further modified by varying amounts of chromium carbide (0, 10 and 20wt.%) in order to develop three

different coatings. Microstructure, elemental mapping XRD, porosity and hardness analysis of the three

coatings was carried out. The effect of CrC concentration (C), load (L), abrasive size (A), sliding distance

(S) and temperature (T) on abrasive wear of these flame sprayed coatings was investigated by response

surface methodology and an abrasive wear model was developed. A comparison of modeled and

experimental results showed 5-9 % error.

Keywords: Coating; Abrasive wear; Microhardness; Response Surface Methodology (RSM).

1 . Introduction

The progressive deterioration of metallic surfaces due to various types of wear (abrasive, erosive,

adhesive, corrosive and chemical wear) in various industries (coal and hydro thermal power plants,

cement, automotive, chemical and cement industry) leads to loss of plant operating efficiency and

frequent breakdown of the components which in turn results in huge financial losses to the industry. The

recognition of this fact has been the driving force behind the continuing development of the surface

modification and surface coating technologies known as surface engineering. The properties of these

surface layers may be different from those of the material as dictated by service requirements.

The cobalt base alloys have found a wide variety of tribological applications for abrasive and

adhesive wear resistance in many industries such as aerospace, automotive, hydro and gas turbines and

cement industry. Some studies [1-6] report the effect of processing techniques, carbide additions and their


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model was evaluated under different abrasive wear conditions by comparing the experimental and

modeled results.

2. Experimental procedure

2.1 Materials and methods

The carbon steel substrate was used for deposition of modified Co base alloy coatings. The

substrate was degreased and roughened to an average surface roughness of Ra 3.15 m (Rmax 18.2 m).

Surface roughness was measured by Mahr Perthometer (M2409). The nominal composition of substrate

and commercially available Co base powder (EWAC 1006 EE) is shown in Table 1. This powder was

modified by adding 20wt.% WC. Further addition of 0, 10 and 20wt.% CrC was carried out to develop

three different compositions ((1006EE + 20wt.% WC+ 0wt.% CrC), (1006EE + 20wt.% WC+ 10wt.%

CrC) and (1006EE + 20wt.% WC+ 20wt.% CrC)). In following sections these modified compositions are

designated by 0, 10 and 20wt.% CrC coatings respectively. These compositions were deposited using

flame spraying process by Super Jet spray torch (L & T India). The flame spraying was carried out using

neutral flame of oxy-acetylene gas where the pressures of oxygen and acetylene were maintained at 0.3

MPa (3kgf/cm2

) and 0.12 MPa (1.2 kgf/cm2

) respectively. The substrate was preheated to 20010o

C. The

spraying parameters are shown in Table 2.

2.2 Characterization of coatings

Coated samples were cut transversely for microstructural characterization (SEM, SEM- LEO 435-

VP, England), porosity and hardness. The samples were polished using standard metallographic

procedure and etched with a chemical mixture of 3 parts HCl + 1 part HNO3. SEM micrographs were

used to study microstructure and worn surfaces. The porosity was measured by the point counting method

[14-20]. The average of 25 areas of each coating has been used for porosity measurement. Vickers

hardness of the coating was measured using a load of 5 kg and average of six readings of the coating was

used for study purpose. Scanning electron microscopy of the worn surfaces of coatings was also carried

out to identify the material removal mechanisms under abrasive wear conditions.


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2.3 Factorial design of experiment

The vast amounts of data have been generated by the traditional approach of experiment design in

which one factor is varied at a time (load and abrasive grit size). In this approach it is difficult to evaluate

the combined effects of applied factors. This is the main reason why load has always been considered first

in wear research, whilst other factors, e.g. abrasive grain size, sliding distance and their combined effects

(load and abrasive size, load and speed, abrasive size and sliding distance), which may also be important,

have not been given the attention they deserve. The advantage of the statistical method is obvious [12].

Thus RSM (Response Surface Methodology) with fractional factorial design of experiments with three

levels of each factor has been used in the present study. According to Rabinowiczs classic theory [21]

that claims applied load and hardness (depends upon composition) of materials are the most important

factors affecting the abrasion process, therefore, both these factors were considered along with the

abrasive size and sliding distance in this study. Temperature is also taken as fifth factor in this study.

Thus five factors composition, load, abrasive size, sliding distance and temperature were used in the

present study. These factors were designated as C (composition- % CrC concentration), L (load-N), A

(abrasive size-m), sliding distance(S) and temperature (T) respectively. The coded value of upper,

middle and lower level of the three factors is designated by +1, 0 and -1 respectively. The actual and

coded values (in parentheses) of various factors used in the present study are shown in Table 3. The

experimental design matrix for different runs is shown in Table 4. The relation between the actual and

coded value of a factor is shown below:

2/

conditionstestofRange

conditionstestMeanconditionstestActualvalueCoded

2.4 Wear test

Wear behavior of flame sprayed coatings (0, 10 and 20wt.% CrC) was studied using pin on disc

type wear testing unit. Coated wear pins of size 5535 mm were held against abrasive medium under

different runs. Water proof SiC abrasive papers were used as abrasive medium. Abrasive paper was

mounted on a steel disc (21020 mm), which was rotated at 2004, 2965 and 3685 rpm (revolution per


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minute) corresponding to the sliding distance of 25, 55 and 85 m. The slide carrying the wear pin was

moved radially to get the spiral motion under a constant increment of 0.2 mm of the wear pin. The

abrasive wear pin and disc carrying the abrasive paper was enclosed in a heating chamber. Three

thermocouples were used for measuring the temperature of the heating chamber. The test temperature was

controlled with the temperature controller unit (target temperature 5C). The tester was allowed to run

idle for 2 minute in order to attain the constant rpm (without reciprocating motion); afterwards load was

applied and simultaneously the reciprocating unit was switched on to have a spiral motion of the wear pin.

Wear tests were conducted randomly according to design matrix (Table 4) under different runs and two

replications under each run were taken and average value of abrasive wear has been reported in Table 4.

An electronic Mettler micro balance (accuracy 0.0001 g) was used for weighing the samples after

washing in acetone before and after abrasive wear. Weight loss was used as a measure of abrasive wear

(g).

3 Results and discussion

3.1 Microstructure

The microstructures and EDAX analysis of 0wt.% chromium carbide, 10wt.% chromium carbide

(not shown for brevity) and 20wt.% chromium carbide coatings are shown in Figs. 1 (a-d) - 2 (a-d)

respectively. The microstructures were taken from the center region of the coatings. All the three coatings

mainly showed eutectic (A), W dominated carbides (B) and Cr dominated carbides (C).

The eutectic A is found to be composed of Co, Ni, Fe and Cr with small amount of W and C.

EDAX analysis of eutectic showed 30% Co, 24% Ni and 15% Fe (wt%) and other elements such as

8%Cr, 6%W, 5%C (wt%) (average of 6 readings in each case has been reported) (Fig. 1b). The W

dominated carbides B and Cr dominated carbides C are present in the eutectic matrix A. These W

and Cr dominated carbide particles primarily differ in terms of relative amounts of various elements such

as W, Cr and Co etc. The EDAX analysis of W dominated carbides showed 57%W, 10% Co, 10% Cr

and 10% Ni and 4%C (wt.%) (Fig. 1c). The Cr dominated carbides C are rich in Cr and contain


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52%Cr, 15%W, 13%Co, 7%C besides small amounts of Ni and Fe (


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be present in the 10wt.% chromium carbide coating (Fig. 5) besides small amount of Cr7C3, FeNi3 and

Ni31Si12 were also observed in 10wt.% chromium carbide coating. Cr7C3as the main carbides was found

in the 20wt.% chromium carbide coating besides Co3W9C4, FeNi3 and Co7W6 phases (Fig. 6). These

finding are in agreement with the published literature [23- 27]. With the addition 10wt.% and 20wt.%

chromium carbide, the carbides types were changed from M23C6 to Cr23C6 and Cr7C3 and some

intemetallic compounds (Co7W6 and Co3W9C4) also formed.

The various types of carbides (M23C6, Cr3C2and Cr7C3) are not pure phases but also contain Ni,

Co, Cr and Fe as revealed by the elemental mapping (Fig. 3 c-1 to c-5) of the various coatings, where Ni,

Co, Cr and Fe are also present in these phases of coatings. As shown by marked circle area C in Fig. 3

c-1, c-3 and c-6, this region may correspond to chromium carbide (Cr7C3as detected by XRD analysis

(Fig. 6). This area C also contains Co, Ni and Fe as shown in Fig. 3 c-2, c-4 and c-5 respectively. Thus,

it is inferred that these carbides are not pure phases. These results are in agreement with the findings of

Chorcia et al. [27].

3.3 Hardness and porosity

The Vickers hardness (Hv5) and porosity (%) of the three coatings with varying wt.% of

chromium carbide (0 wt.% chromium carbide, 10 wt.% chromium carbide and 20wt.% chromium

carbide) are shown in Fig. 7 (a) and (b) respectively. Vickers hardness of three coatings was measured

using a normal load of 5kg and average value of six readings of hardness of the coating cross-section has

been used for study. The average Vickers hardness (Hv5) of three coatings (0 wt.% chromium carbide, 10

wt.% chromium carbide and 20 wt.% chromium carbide) was found to be 69686 Hv5, 74195 Hv5and

786112 Hv5 respectively (Fig 7a). The average hardness of 20wt.% chromium carbide coating was

found higher (786 Hv5) as compared to 0 wt.% chromium carbide (696 Hv5) and 10 wt.% chromium

carbide (741 Hv5) coatings, however, there was a more scatter in hardness of 20 wt.% chromium carbide

coating as compared to 0 wt.% chromium carbide and 10% chromium carbide coatings may be due to

higher porosity (Fig. 7b).


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The higher hardness of 10 wt.% chromium carbide coating as compared to 0 wt.% chromium

carbide is due to formation of Cr23C6carbides and intemetallic compound Co7W6 as detected by XRD

analysis (Fig. 5). The highest hardness of 20 wt.% chromium carbide coating as compared to other two (0

wt.% chromium carbide and 10 wt.% chromium carbide) is mainly due to formation of Cr7C3carbides as

detected by XRD analysis (Fig. 6). The formation of Cr7C3 and Cr23C6 carbides increases the hardness of

the coating owing to their high hardness. The hardness of Cr7C3 and Cr23C6 is 17.7 GPa and 9.9 GPa

respectively as reported by Lebaili et al. [28]. It has also been reported [24, 25] that some of the

chromium may be replaced by cobalt and/or tungsten with a matrix of eutectic containing the other

constituents of the alloy, thus forming intermetallic compounds. In this investigation also it has been

observed that Co7W6and Co3W9C4intermetallic compounds were formed as found in the XRD analysis

of 10 wt.% chromium carbide and 20 wt.% chromium carbide coating (Fig. 5, 6). Otterloo et al. [24, 25]

reported that the intermetallic compounds (Co7W6and Co3W9C4) also increase the hardness of Co-base

alloys. Thus, the higher hardness of 10 wt.% chromium carbide and 20 wt.% chromium carbide coatings

can also be attributed to formation of these intermetallic compounds as detected by XRD analysis (Fig. 5,

6). The porosity of all the three coatings was found to be 7.7%, 8.6% and 9.2% respectively (Fig. 7b).

3.4 Abrasive wear model

In the present work RSM was applied for developing the mathematical models in the form of

multiple regression equations for the abrasive wear. In applying the RSM the dependent variable

(abrasive wear) is viewed as a surface to which the model is fitted. Evaluation of the parametric effects on

the response (abrasive wear) was done by considering a second order polynomial response surface

mathematical model given by:

rji

k

i

k

ij

ijiii

k

i

i

k

i

i xxbxbxbbWr

1

1 1

2

11

0 (1)

This equation of abrasive wear (assumed surface) Wr contains linear, squared and cross product

terms of variable xis (C, L, A, S and T). b0is the mean response over all the test conditions (intercept), bi


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is the slope or linear effect of the input factor x i (the first-order model coefficients), bii the quadratic

coefficients for the variable i(linear by linear interaction effect between the input factor xiand xi) and bij

is the linear model coefficient for the interaction between factor i and j. The face centered composite

design was used in this experimental study. Significance testing of the coefficients, adequacy of the

model and analysis of variance was carried out to using Design Expert Software to find out the significant

factors, square terms and interactions affecting the response (abrasive and erosive wear). R is the

experimental error.

The analysis of variance (ANOVA) is shown in Table 5. The analysis of variance (ANOVA)

shows the significance of various factors and their interactions at 95% confidence interval. ANOVA

shows the Model as Significant while the Lack of fit is Not significant which are desirable from

a model point of view. The probability values < 0.05 in the Prob.>F column indicates the significant

factors and interactions. The main factors and their interactions are included in the final abrasive wear

model while the insignificant interactions are excluded from the abrasive wear model. Composition (C),

load (L), abrasive size (A) and sliding distance (S) are the significant factors while composition-load

(CL), composition-temperature (CT), load-abrasive size (LA), load-sliding distance (LS) and abrasive

size-sliding distance (AS) are the significant interactions. The abrasive wear model generated in terms of

coded and actual factor values (equation 2 and 3 respectively) is given below:

Wr =0.015 - 4.86 10-3C + 0.013 L + 9.73 10-3A + 0.016 S 2.3310-4 T + 9.9510-3S2 -3.310-3CL

+ 4.2710-3CT + 5.4510-3LA + 8.1310-3LS + 8.42 10-3AS R (2)

Wr =0.053 8.46 10-4C -7.19 10-4L 3.47 10-4A 1.5210-3S 9.02 10-5 T + 1.1110-5S2 -

3.310-5

CL + 8.5510-6

CT + 1.3610-5

LA + 2.7110-5

LS + 7.02 10-6

AS R (3)

3.5 Validity of the abrasive wear model

The validity of the abrasive wear model was evaluated by conducting abrasive wear tests on

coatings at different values of the experimental factors such as applied load (L), abrasive sizes (A), sliding


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distance(S) and temperature (T). The actual and coded value of various factors for confirmation tests are

shown in Table 6. The variations between the experimental and the calculated values are of the order of

59%.

3.6 Effect of individual variables on wear rate

The effect of individual factors on abrasive wear is shown in Fig. 8 (a-e). The effect of

composition (C), load (L), abrasive size (A), sliding distance(S) and temperature (T) and that of their

interactions on abrasive wear are given in equation (2) which exhibits the abrasive wear in terms of coded

value and equation (3) in terms of actual values of factors and their interactions. However, the effects of

individual factors are discussed by considering the equation (2) because all the factors are at the same

level (+1, 0 and -1). The constant 0.015 in the equation (2) indicates the overall mean of the abrasive wear

of coatings under all the test conditions. This equation further indicates that the coefficient (-4.8610 -3)

associated with composition (%CrC concentration) is negative, which signifies a decrease of abrasive

wear with an increase of CrC concentration (Fig. 8 a). This is attributed to the increase in hardness of the

coating with increasing CrC concentration. Increase in hardness of material lowers the depth of

penetration of abrasive particles, therefore, results in shallow and finer wear grooves and reduced volume

of material removed. The effect of load, abrasive size, sliding distance and temperature on abrasive wear

is shown in Fig. 8 (b-e). The coefficient associated with load, abrasive size, sliding distance and

temperature are 0.013, 9.7310-30.016 and -2.3310-4respectively. This signifies that sliding distance has

a more detrimental effect than the applied load on the abrasive wear of the coating. This is due to the fact

that the load determines the depth of penetration of abrasive in the material whereas there is a prolonged

interaction of abrasives at higher sliding distances. Thus, for the same load the abrasive wear increases

with the increase in sliding distance as shown in Fig. 8d. The effect of abrasive size on the wear is less as

compared to sliding distance and load. The abrasive wear increases with the increase in abrasive size (Fig.

8) as there is a greater tendency for large penetration of sharp abrasives with the increase of abrasive size,

attributed to increase in actual contact area and hence the effective load [12]. This leads to deeper and

wider grooves and finally causes more severe wear of the coating. The penetration of the small size


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abrasives is limited to its height of projection in the specimen surface. Thus the depth of penetration is

reduced even with the increase in load on small abrasive sizes which results in reduced wear of coatings.

The reduction in abrasive wear at higher temperature may be due to removal of some abrasive particles

from the abrasive paper.

3.7 Interaction effect of the different variables

The coefficients associated with the interaction terms CL (composition-load), CT (composition-

temperature), LA (load-abrasive size), LS (load-sliding distance) and AS (abrasive size-sliding distance)

in equation (2) are -3.310-3, 4.2710-3, 5.4510-3, 8.1310-3 and 8.42 10-3 respectively showed the

extent of interaction (combined) effect of different factors on abrasive wear of coatings. The effect of

interactions among the different factors on abrasive wear is almost same order as of their individual

effects. The combined effect of composition -load (CL) is the lowest from all significant interactions.

The combined effect of various abrasive wear test parameters on the wear behavior of coatings

has been shown in the form of response surface plots (Fig. 9 a-e). The combined effect of CL

(composition-load) interaction can be explained by considering equation 2 and Fig. 9 (a). The ve sign

associated with the coefficient of CL interaction shows the reduction in wear of the coating. The Fig.9 (a)

shows that the abrasive wear increases with the increase in load due to more penetration effect of abrasive

in the coating while the wear reduces due to increase of CrC concentration from 0 to 20wt.%. The

reduction in wear at high CrC concentration is due to increase in hardens of coating. The overall effect of

CL interaction is to reduce the wear of the coating. The CT (composition-temperature) interaction can be

explained on similar lines by considering equation 2 and Fig. 9 (b).

The combined effect of load and abrasive size (LA) on wear of coatings shows that the wear of

coatings increases with an increase in both the load and abrasive size. Moreover, the effect of increase in

load at high abrasive size is more predominant than at low abrasive size. Further, it can be observed from

response surface plot that the effect of increase in abrasive size on wear of coatings is more at high loads

than at low loads. This is attributed to the fact that at high load and large abrasive size, the depth of


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The chromium carbide concentration increases the wear resistance of the coatings. Experimental

and confirmation test results showed that the weight loss in 20% CrC coating is lowest. The weight loss

of 20% chromium carbide coating is 1.5 times lower as compared to 0% chromium carbide coating. This

is attributed to higher hardness of the coating.

4 Conclusions

The following conclusions can be drawn from the present study:

1. The hardness increases with the increases in chromium carbide concentration. The maximum hardness

was obtained with 20wt.% chromium carbide. The increase in hardness is due to formation of new

phases and inetrmetallic compounds.

2. Response Surface Methodology (RSM) with fractional factorial design approach is an excellent tool,

which can be successfully used to develop an empirical equation for the prediction and understanding

of wear behavior of coatings in terms of individual factors (C, L, A, S and T) as well as in terms of the

combined effects (CL, CT, LA, LS and AS) of various factors.

3. The load and sliding distance has a more severe effect on abrasive wear of the coating as compared to

abrasive size.

4. Interactions effects of various factors on abrasive wear is almost of same order less than their main

factor effects. The interaction effect of abrasive size-sliding distance (AS) is considerably higher than

load-abrasive size (LA). Increasing (%) CrC concentration; reducing load, abrasive size and sliding

distance minimize the abrasive wear significantly.

5. Increase in chromium carbide concentration increases the abrasive wear resistance of the coatings.

Abrasive wear rate of 20wt.% chromium carbide coating is lower as compared to 0wt.% chromium

carbide coatings.

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Table Captions

Table 1 Chemical composition (wt. %) of substrate and surfacing powder

Table 2 Flame spray parameters

Table 3 Various factors and their levels

Table 4 Design matrix and various factors with their actual and coded values (in parentheses)

Table 5 Analysis of variance (ANOVA)

Table 6 Confirmations test results


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2 20 (+1) 25 (+1) 20 (-1) 85 (+1) 50 (-1) 0.0209

3 0(-1) 15 (0) 60 (0) 55 (0) 100 (0) 0.0146

4 10 (0) 25 (+1) 60 (0) 55 (0) 100 (0) 0.0215

5 10 (0) 15 (0) 100 (+1) 55 (0) 100 (0) 0.0172

6 0(-1) 25 (+1) 100 (+1) 85 (+1) 50 (-1) 0.104

7 10 (0) 15 (0) 20 (-1) 55 (0) 100 (0) 0.0061

8 10 (0) 5 (-1) 60 (0) 55 (0) 100 (0) 0.0066

9 20 (+1) 25 (+1) 100 (+1) 25 (-1) 50 (-1) 0.0151

10 10 (0) 15 (0) 60 (0) 55 (0) 150 (+1) 0.0144

11 20 (+1) 15 (0) 60 (0) 55 (0) 100 (0) 0.0147

12 10 (0) 15 (0) 60 (0) 55 (0) 100 (0) 0.0161

13 0(-1) 5 (-1) 100 (+1) 85 (+1) 150 (+1) 0.0338

14 20 (+1) 25 (+1) 20 (-1) 25 (-1) 150 (+1) 0.0057

15 20 (+1) 5 (-1) 20 (-1) 25 (-1) 50 (-1) 0.0028

16 0(-1) 25 (+1) 100 (+1) 25 (-1) 150 (+1) 0.0205

17 0(-1) 5 (-1) 20 (-1) 85 (+1) 50 (-1) 0.012

18 0(-1) 5 (-1) 20 (-1) 25 (-1) 150 (+1) 0.0051

19 10 (0) 15 (0) 60 (0) 25 (-1) 100 (0) 0.0048

20 0(-1) 25 (+1) 20 (-1) 85 (+1) 150 (+1) 0.0473

21 10 (0) 15 (0) 60 (0) 85 (+1) 100 (0) 0.0356

22 20 (+1) 5 (-1) 20 (-1) 85 (+1) 150 (+1) 0.0097

23 20 (+1) 25 (+1) 100 (+1) 85 (+1) 150 (+1) 0.0778

24 20 (+1) 5 (-1) 100 (+1) 85 (+1) 50(-1) 0.0237

25 20 (+1) 5 (-1) 100 (+1) 25 (-1) 150 (+1) 0.0039

26 10 (0) 15 (0) 60 (0) 55 (0) 50(-1) 0.0194

27 0(-1) 5 (-1) 100 (+1) 25 (-1) 50 (-1) 0.0066

28 10 (0) 15 (0) 60 (0) 55 (0) 100 (0) 0.0151

29 10 (0) 15 (0) 60 (0) 55 (0) 100 (0) 0.0188

30 10 (0) 15 (0) 60 (0) 55 (0) 100 (0) 0.0142

Table 5 Analysis of variance (ANOVA)


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20

Source Sum

Squares

Degrees

Of

Freedom

Mean

Square

F

Value

Prob>F

Model 0.013 11 1.2110-3 48.45 < 0.0001 Significant

Composition- C 4.2510-4 1 4.2510-4 17.10 0.0006

Load-L 2.85010-3 1 2.85010-3 114.58 < 0.0001

Abrasive size

A

1.70310-3 1 1.70310-3 68.48 < 0.0001

Sliding

distance- S

4.43110-3 1 4.43110-3 178.12 < 0.0001

Temperature -

T

9.80010-7 1 9.80010-7 0.039 0.8449

Interaction CL 1.74210-4 1 1.74210-4 7.00 0.0164

Interaction CT 2.9210-4 1 2.9210-4 11.76 0.0030

Interaction LA 4.75210-4 1 4.75210-4 19.11 0.0004

Interaction LS 1.05610-3 1 1.05610-3 42.46 < 0.0001

Interaction AS 1.13610-3 1 1.13610-3 45.66 < 0.0001

Residual error 4.47710-4 18 2.48710-5

Lack of fit 4.35810-4 15 2.90610-5 7.33 0.0632 Not

significant

Pure error 1.18910-5 3 3.96310-6

Table 6 Confirmations test results


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21

Composition (C)

% CrC

Load

(L),

N

Abrasive

size(A) m

{grit size}

Sliding

distance

(S) m

Temperature

(T) C

Modeled

abrasive

wear (g)

Experimental

abrasive wear

(g)

%

Error

0 (-1) 15 (0) 422

{320}(-0.5)

70 (+0.5) 100 (+0.5) 0.0238 0.0250 4.8

10 (0) 15 (0) 422 {320}

(-0.5)

70 (+0.5) 100 (+0.5) 0.019 0.0173 8.95

20 (+1) 15 (0) 422 {320}

(-0.5)

70 (+0.5) 100 (+0.5) 0.0141 0.0152 7.24


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22

Research Highlights

The hardness increases with the increases in chromium carbide concentration.

The load and sliding distance has more severe effect on abrasive wear of coating.

Abrasive wear rate of 20wt.% chromium carbide coating is lower as compared to 0wt.%.


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19

Fig. 1 Microstructure and EDAX analysis of 0wt.% chromium carbide coating (a)

microstructure of coating, (b) EDAX analysis of eutectic, (c) EDAX analysis of

W dominated carbide and (d) EDAX analysis of Cr dominated carbide.

Eutectic A

c

b

dW dominatedcarbides B Cr dominated

Carbides C

Cr dominatedCarbides C

EutecticA

W dominatedcarbides B

aEutectic A


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20

Fig. 2 Microstructure and EDAX analysis of 20wt.% chromium carbide coating (a)

microstructure of coating, (b) EDAX analysis of eutectic, (c) EDAX analysis of

W dominated carbide and (d) EDAX analysis of Cr dominated carbide.

a

Eutectic A W dominatedcarbides B


c

b

d

Eutectic A

W dominatedcarbides B



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21

(a)

(b)

(c)

Fig.3Continued.

Co

Co

C

o

3a-1

3a-2

3b-2

3c-2

3b-1

3c-1

AreaC

AreaC


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22

(a)

(b)

(c)

Fig.3Continued.

Cr

Ni

Cr

C

r

N

i

Ni

3a-3

3a-4

3b-4

3c-4

3b-3

3c-3

AreaC

AreaC


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23

(a)

(b)

(c)

Fig.3Elementalmaps

showingthedistributionofCo,Cr,Ni,Fe,andCin(a)0wt.%c

hromiumcarbide,(b)10wt.%c

hromi

umcarbideand

(c)20wt.%ch

romiumcarbidecoatings.

Fe C

Fe

Fe C

C

3a-5

3a-6

3b-6

3c-6

3b-5

3c-5

AreaC

AreaC


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24

4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

Fig. 4 XRD spectrum showing various phases in 0 wt.% chromium carbide coating.

4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

1 8 0

Fig. 5 XRD spectrum showing various phases in 10wt.% chromium carbide coating.

4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

1 8 0

2 0 0

2 2 0

Fig. 6 XRD spectrum showing various phases in 20wt.% chromium carbide coating

1- Ni-Cr-Fe-C

1, 3,5, 6

2- M23C6

1, 2, 3 2

3- Ni4W

4

4- CoWSi

4

6- Fe2O3

7

56

5- Fe3C 7- NiO2

8- Cr2O3

5

8 78

5- FeNi31- Cr23C6 2- Cr7C3 3- Co7W6 4- WSi2

1, 2, 3, 4,

1, 2, 531

4

11

1

1, 2, 3, 4

1- Cr7C3 2- Co3 W9 C4 3- Ni31 Si12 5- FeNi34- Fe3C

3, 51

21

54

Relativ

eIntensity

Diffraction angle 2

RelativeIntensity

RelativeIntensity

Diffraction angle 2

Diffraction angle 2


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25

640

660

680

700

720

740

760

780

800

0 wt.% 10 wt.% 20 wt.%

Vickershardness(Hv5)

Wt.% Chromium carbide

0

1

2

3

4

5

6

7

8

9

10

0 wt.% 10 wt.% 20 wt.%

P

orosity(%)

Wt.% Chromium carbide

Fig. 7 Effect of chromium carbide addition in 1006-20wt.%WC powder coating

on (a) hardness (Hv5) and (b) porosity (%).

0.00 5.00 10.00 15.00 20.00

0.0028

0.0281

0.0534

0.0787

0.104 a

Composition (C), wt.%CrC

Abrasivewear,g

:

25.00 40.00 55.00 70.00 85.00

0.0028

0.0281

0.0534

0.0787

0.104 d

Sliding Distance (S), m

Abras

ivewear,g

20.00 40.00 60.00 80.00 100.00

0.0000

0.0153

0.0306

0.0459

0.0612 c

Abrasive size (A), m

Abras

ivewear,g

5.00 10.00 15.00 20.00 25.00

-0.0005

0.0150

0.0304

0.0458

0.0612

Load (L), N

b

Abrasivewear,g

69686

74195

786112a b

7.7

8.69.2


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26

Fig. 8Effects of individual factors such as (a) %CrC-concentration (C), (b) load (L), (c)

abrasive size (A) (d) sliding distance (S) and (e) temperature (T) on abrasive

wear.

50.00 75.00 100.00 125.00 150.00

0.0028

0.0281

0.0534

0.0787

0.104 e

Temperature (T), C

Abrasiv

ewear,g

0.0000

0.0153

0.0306

0.0459

0.0612

0.00

5.00

10.00

15.00

20.00

5.00

10.00

15.00

20.00

25.00

a

Abrasivewear,g

Load (L), N

0.0000

0.0153

0.0306

0.0459

0.0612

0.00

5.00

10.00

15.00

20.00

50.00

75.00

100.00

125.00

150.00

b

Abrasivewear,g

Temperature

(T), CComposition (C),

wt.%CrC

Composition (C),

wt.%CrC


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27

Fig. 9 Effects of interactions (a) composition-load (CL), (b) composition-temperature

(CT), (c) load-abrasive size (LA), (d) load-sliding distance (LS) and (e) abrasive

size and-sliding distance (AS) on abrasive wear.

0.0000

0.0153

0.0306

0.0459

0.0612

5.00

10.00

15.00

20.00

25.00

20.00

40.00

60.00

80.00

100.00

c

Abrasivewear,g

Abrasive size

(A), m

0.0000

0.0153

0.0306

0.0459

0.0612

5.00

10.00

15.00

20.00

25.00

25.00

40.00

55.00

70.00

85.00

d

Abrasive

wear,g

Sliding Distance

(S), m

0.0000

0.0153

0.0306

0.0459

0.0612

20.00

40.00

60.00

80.00

100.00

25.00

40.00

55.00

70.00

85.00

e

Abrasivewear,g

Sliding Distance

(S), m

Load (L), NLoad (L), N

Abrasive size(A), m


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Fig.10 SEM micrographsof worn surfaces (a) 0%wt. chromium carbide, (b) 10%wt. chromium

carbide .

b

Cutting

a

Ploughing

Sliding Direction

parametric study of abrasive wear of co crc based flame sprayed coatings by response surface...

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