The study of corrosion–wear mechanism of Ni–W–P alloy

F.J. He n, Y.Z. Fang, S.J. JinState Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China

a r t i c l e i n f o

Article history:Received 13 July 2013Received in revised form25 December 2013Accepted 31 December 2013Available online 8 January 2014

Keywords:Ni–W–P alloyHardnessCorrosion–wearWear mechanismSynergy effect

a b s t r a c t

The wear resistance of Ni–P alloys can be improved by the addition of W; however, it is not wellunderstood how that addition will affect the corrosion–wear characteristics of the alloy. Therefore, a Ni–W–P alloy was prepared by electrodeposition and used for tribo-testing. The corrosion–wear behavior ofthe alloy, both in the as-prepared and heat-treated states, was investigated using a submerged ball ondisk apparatus in deionized water and in 3.5 wt% NaCl solution. The ball material was Cr bearing steel.The 400 1C heat-treated Ni–W–P alloy had the minimum wear rate in both deionized water and 3.5 wt%NaCl solution. In the 3.5 wt% NaCl solution, the heat-treated alloy displayed pitting and abrasive wear.The Ni–W–P alloy as-prepared, showed uniform corrosion. Its main wear process was corrosive, and itshowed adhesive wear when tested in the 3.5 wt% NaCl solution. In deionized water, the wear of theNi–W–P alloy was caused by abrasion whether as-prepared or heat-treated. A synergy effect betweenwear and corrosion existed in Ni–W–P alloy, both in the as-prepared and heat-treated states when testedin a saline environment.

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1. Introduction

The corrosion–wear behavior refers to the material loss whichis caused by mechanical wear and associated with chemical orelectrochemical corrosion. It widely exists in the equipment of coalmining, oil and chemical engineering, and electricity industrial etc.during their service processes. The material failure, which iscaused by corrosion and wear, has resulted in a huge loss to thenational economy [1–3].

As a discipline Friction and Wear emerged in the 1960s. Thetopic about corrosion–wear appeared more recently. It attracts thepeople0s interest because of its great harm and serious damages.The material failure caused by corrosion–wear was not merelya summation of static corrosion and mechanical wear, but muchlarger than that. In the corrosion–wear environment, materialfailure is usually accelerated by synergistic interaction betweenthe mechanical action of wear/rubbing and the corrosion reactionsoccurring on the wear surfaces. A lot of research works have beenreported on the corrosion–wear synergy effect [4–12]. Lee [13]investigated the synergy between corrosion and wear of Ni–Pelectrodeposits in NaCl solution using a block-on-ring testerapparatus. Sun [14] studied the tribocorrosion behavior of AISI304 stainless steel under unidirectional sliding in 0.5 M NaClsolution using a pin-on-disk tribometer integrated with a poten-tiostat for electrochemical control. Bateni [15] investigated wear

and corrosion–wear of medium carbon steel and 304 stainlesssteel in 3.5 wt% NaCl solution using a pin-on-disk tribometer toperform wear and corrosive wear tests. Dong [16] studied ontribological properties of Al2O3 ceramics/1Cr18Ni9Ti stainless steelrubbing pairs using a MMW-1 tribo-tester under pure water anddifferent concentrations of hydrogen peroxide (H2O2) solutions.Ma [17] investigated the tribological properties of a Fe3Al materialin an aqueous solution of 1 M H2SO4 corrosive environment slidingagainst a Si3N4 ceramic ball. It is of significant practical importancefor such research in many engineering systems, where materialsforming tribological contacts are exposed to a corrosive environ-ment in various forms. The study of corrosion–wear mechanism isvery important for reducing the loss of the material, the properuse of metals and alloys and the control of corrosion–wear rate.

Ni–W–P alloy has characteristics of high hardness, high wearresistance, high thermal stability, good corrosion resistance. Pala-niappa [18] studied the deposition and tribological characteristicsof electroless binary Ni–P and ternary Ni–W–P alloy coatings. Theexperimental results proved that coatings with high tungstencontent exhibited very good wear resistance compared to binaryNi–P as well as low tungsten ternary alloy deposits. Gao [19]investigated the effect of the nanostructure itself on corrosionresistance without the influence of the second phase Ni3P in Ni–Pand Ni–W–P deposits. It was found that the as-plated nanocrystal-line deposits, whether the binary Ni–P or the ternary Ni–W–Palloys, and the annealed binary Ni–P alloy films, had much lowercorrosion resistance than their amorphous counterparts. Lu [20]investigated the corrosion resistance of Ni–P alloy and Ni–P–W orNi–P–Mo alloys. The results showed that addition of W to Ni–P

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0043-1648/$ - see front matter & 2014 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.wear.2013.12.024

n Corresponding author. Tel.: þ86 731 82710201; fax: þ86 731 88808630.E-mail address: fengjiao87799232@hotmail.com (F.J. He).

Wear 311 (2014) 14–20

alloys can improve their corrosion resistance. Addition of Mo haslittle or no beneficial effects on corrosion properties. It has greateconomic value and practical significance using Ni–W–P alloy tosolve some industrial equipment corrosion–wear problems. So far,there are few studies on the corrosion–wear mechanism of Ni–W–

P alloy. In this paper, the corrosion–wear properties and mechan-isms of electrodeposited Ni–W–P alloy in as-prepared and 400 1Cheat treatment states were studied in detail, and it also lays downan important theoretical basis for the application of Ni–W–P alloy.

2. Experimental work

Ni–W–P alloys were prepared by proprietary solution (Patentnumber: 03124792) supplied by Hunan Nanofilm New MaterialTechnology Co. Ltd. Ni–P alloys were prepared using the methodreported in the book [21]. The thicknesses of all alloys wereapproximately 50 μm.

The surface morphology was observed with a S4800 scanningelectron microscope (JEOL Ltd., Japan). In order to determine thestructure of as-prepared and heat-treated Ni–W–P alloy, X-raydiffraction (XRD) measurements were made with a Rigaku D/max-rA diffractometer using CuKα radiation generated from a Cu targetat 50 kV and 100 mA.

Microhardness studies were done using HVS-1000 digitalmicrohardness tester with a Vickers indenter. A constant load of200 g was applied for 10 s each to cause the indentations in all thedeposits and the hardness values were averaged out of five suchdeterminations.

The corrosion behaviors have been evaluated by immersingalloy samples vertically in 3.5 wt% NaCl solution for 600 h at roomtemperature. The corrosion rates were determined by the weight-loss after immersion and expressed in mg/(cm2 h). Alloys had fixedexposed area of 8 cm2 by protected extra area with gelatinizinginsulating lacquer with an approximately 50 μm thickness.

All experiments were carried out on a MMW-1 tribo-tester,which was made by Chenda Group in China. The diagram wasshown in Fig. 1.

Ni–W–P alloy was deposited on a 45♯ steel ring with anexternal diameter of 32 mm and an inner diameter of 11 mm.The thickness of the ring was approximately 10 mm. The counter-part was GCr15 ball sample with 10 mm diameter.

The sliding wear tests of the Ni–W–P alloys and GCr15 ballrubbing pairs were conducted in deionized water and 3.5 wt% NaClsolution. The rotational speed of the tester was 150 rpm with anominal load 150 N for 120 min. Three replicate wear tests werecarried out so as to minimize data scattering, and the average ofthe three replicate test results were reported in this work. Thewear mass losses of Ni–W–P alloys were measured using METTLERelectronic balance with precision of 0.1 mg. The worn surfacemorphologies were observed with a S4800 scanning electronmicroscope.

3. Results

3.1. Characterization of Ni–W–P alloy and Ni–P alloy

Chemical compositions of the as-prepared Ni–W–P alloy andelectroless plated Ni–P alloy determined by EDS were shown inTable 1. The results showed that Ni–W–P alloy consisted of 2.85 wt% P, 29.9 wt% W, 67.26 wt% Ni and Ni–P alloy consisted of 4.53 wt%of P, and 95.47 wt% of Ni. The morphologies of the as-preparedNi–W–P alloy and electroless plated Ni–P alloy were shown inFigs. 2 and 3 respectively. Ni–W–P alloy exhibited a smoothsurface with very fine and smaller nodules, while the Ni–P alloyexhibited less number of individual and agglomerated noduleswith no regular arrangement.

3.2. Properties evaluation

3.2.1. Microhardness measurementThe effect of heat treatment on the hardness of the Ni–W–P

alloy was shown in Fig. 4. Samples were annealed in a mufflefurnace for 2 h in open-air atmosphere under various tempera-tures (room temperature, 200, 300, 400, 500 and 600 1C). As isclearly evident, the hardness of the alloy increased with anincrease in the annealing temperature, and the peak value corre-spond to 400 1C, and then dropped at higher temperature.

3.2.2. X-ray diffraction patterns of Ni–W–P alloyX-ray diffraction patterns of Ni–W–P alloy as-prepared and in

different anneal heat treatment temperature state were shown inFig. 5. For as-prepared and heat-treated at 200 1C Ni–W–P alloysamples, their pattern of XRD presented a broad peak character-istic of an amorphous structure. Their crystalline phases were asupersaturated solid solution of P and W in Ni matrix and W atomoccupied Ni atom position. For sample heat-treated at 400 1C, itsXRD diffraction pattern displayed a sharp peak, and a character-istic relating to Ni3P, and Ni4W phases were observed. More well-defined peaks were visible in the diffraction diagram of the sampleheat-treated at 600 1C, indicating the formation of new crystallinephases possibly related to Ni and Ni–W phases.

3.2.3. Corrosion resistanceThe corrosion rates of Ni–W–P alloys as-prepared and heat-

treated which immersed in the 3.5 wt% NaCl solution at roomtemperature were shown in Table 2. It was observed that all thesealloys showed corrosion rates lower than 1.11E�03 mg/(cm2 h).The corrosion rates of the alloys were shown as-prepared Ni–W–

Poheat-treated Ni–W–P, i.e. As for as-prepared Ni–W–P alloy, ithad higher corrosion resistance than alloy in heat treatment state.For the Ni–W–P alloy heat-heated at 400 1C, it showed the highestcorrosion rate. When heated beyond this temperature, the corro-sion rate was found to decrease. The corrosion rates of Ni–P alloysin the as-prepared and heat-treated states were much higher thanthat of Ni–W–P alloys.

Ball sample

Ni-W-P alloy

coating

Oil box

Medium

Fig. 1. A schematic sketch of the MMW-1 tribo-tester.

Table 1Composition of as-prepared Ni–W–P alloy and Ni–P alloy determined by EDSanalysis.

Alloy Chemical composition (wt%) Chemical composition (at%)

Ni W P Ni W P

Ni–W–P 67.26 29.90 2.85 81.82 11.61 6.56Ni–P 95.47 – 4.53 91.74 – 8.26

F.J. He et al. / Wear 311 (2014) 14–20 15

3.3. Tribological behavior

3.3.1. Wear ratesThe effect of annealing temperature on the wear rates of Ni–

W–P alloys in deionized water and 3.5 wt% NaCl solution wereindividually shown in Fig. 6. The wear rate of the alloy increasedslightly when the heat treatment temperature was under 200 1C,and then it began to decrease as temperature went up. Theminimum of wear rate was observed for alloy heat-treated at

400 1C in both deionized water and 3.5 wt% NaCl solution. Therewas a further increase in the wear rate values when heat treat-ment temperature was higher than 400 1C. This trend was theresult of mutual interactions among the hardness, wear resistanceand corrosion resistance. Therefore Ni–W–P alloys as-preparedand 400 1C heat-treated were chosen for further study.

An interesting thing was found in Fig. 6 when comparing wearrates of alloys immersed in deionized water and 3.5 wt% NaClsolution. When the heat treatment temperature was lower than400 1C, the wear rates in deionized water were lower than those in3.5 wt% NaCl solution; while when the heat treatment tempera-ture was higher than 400 1C, the wear rates in deionized waterwere higher than those in 3.5 wt% NaCl solution.

For comparison, the wear rates of Ni–P alloys in deionizedwater and in 3.5 wt% NaCl solution were shown in Table 3. Testingduration was 30 min. The results showed that the wear rates weremuch higher than the Ni–W–P alloys under the same conditions.

3.3.2. Friction coefficientThe friction coefficient of Ni–W–P alloys as-prepared and heat-

treated in deionized water and 3.5 wt% NaCl solution were shownin Fig. 7. The coefficient of friction detected in deionized water wasfound to be more fluctuating compared with those detected in3.5 wt% NaCl solutions. In 3.5 wt% NaCl solution, the averagecoefficient of friction of Ni–W–P alloys in as-prepared state andheat-treated at 400 1C state was 0.51 and 0.45, respectively. Indeionized water the average friction coefficient was 0.37 and 0.41,respectively.

It also could be observed that the coefficient of friction of allsamples showed an increasing trend under the corrosive environ-ment. The corrosive solution reduced the friction between thesubstrate and the counter-face, which consequently decreased thecoefficient of friction. On the other hand, due to the surfacechemical reaction occurred at the same time, the surface rough-ness increased in 3.5 wt% NaCl solution. Because of the mutualinteractions of these factors, the friction coefficient showed com-plex changes.

3.3.3. Microstructure of worn samplesSEM micrograph of worn surface morphologies of Ni–W–P

alloys as-prepared and 400 1C heat-treated in deionized waterwere shown in Fig. 8a and b. Bright and smooth plow markers indifferent sizes could be seen. The relative motion of two surfaces

Fig. 2. Scanning electron micrograph of Ni–W–P alloy produced by dcelectrodeposition.

Fig. 3. Scanning electron micrograph of Ni–P alloy produced by electrolessdeposition.

0 100 200 300 400 500 600600

650

700

750

800

850

900

Fig. 4. The microhardness of as-prepared and heat-treated Ni–W–P alloys.

Fig. 5. X-ray diffraction patterns of Ni–W–P alloy annealed at different tempera-tures for 2 h.

F.J. He et al. / Wear 311 (2014) 14–2016

induced plastic deformation. The alloy in as-prepared stateshowed deep plow marker and exhibited fine grooves along thesliding direction in heat treatment state. This was caused byhardness difference for alloy as-prepared and in heat treatmentstate. Bright and smooth markers also meant no corrosion indeionized water.

Fig. 8c–f showed a worn surface morphology (50 times magni-fication) of the Ni–W–P alloys as-prepared and 400 1C heat-treated in 3.5 wt% NaCl solution. Fig. 8c and d were correspondingto alloys as-prepared and 400 1C heat-treated individually in 50

times magnification, and Fig. 8e and f were in 500 times magni-fication. Exfoliation markers were seen in SEM morphology.Compared with the wear in deionized water Fig. 8(a and b), wornsurfaces in 3.5 wt% NaCl solution were more serious. Although theproperty of alloy in as-prepared state against 3.5 wt% NaCl solu-tion corrosion was better than that in 400 1C heat-treated state(see Table 3), the worn surface of as-prepared alloy (Fig. 8c and e)experienced a more severe wear than that of 400 1C heat treat-ment alloy (Fig. 8d and f) under the same conditions. Large area ofthe oxide layer, a small amount of peeling, pits and shallowscratches were detected. Deep color region in the figure may bean oxide layer generated in the corrosive medium. Because of thebrittleness of the oxide layer, it could easily fall off by the externalforce. Part of the oxides fell off from the friction system, anotherpart of the oxides were ground into small granular rolling in thepeeling area and caused abrasive wear.

SEMmorphology of the electroless plating Ni–P alloy in 3.5 wt%NaCl solution was shown in Fig. 8g. The delamination flake couldbe observed from the SEM picture. Compared with Ni–W–P alloysin different heat treatment states, electroless plating Ni–P alloyshowed a higher wear rate, lower corrosion resistance and poorerwear performance.

4. Discussion

4.1. Corrosion-wear behavior of Ni–W–P alloy

The deionized water was a little corrosive to Ni–W–P alloy.It acted as lubricant during the wear process and decreased thewear loss of alloy. EDS detection results of worn Ni–W–P alloyin deionized water were shown in Table 4. Phosphorus elementdisappeared after wear, which might be caused by the formationof soluble phosphate films. For as-prepared Ni–W–P alloy, theNi/W atomic ratio increased from 7.0 to 10.49 before and afterwear. It was argued that W, which had a larger atomic size than Ni,occupied Ni position in matrix and enlarged and distorted the Nilattice. The bonding force between Ni and W atoms were weakerthan Ni and Ni atoms. During the sliding wear process of Ni–W–Palloy, W atom was preferentially peeled off than Ni. Therefore theNi/W atomic ratio increased after wear. For Ni–W–P alloys heattreated at 400 1C, Ni/W atomic ratio reduced from 9.96 to 6.37before and after corrosive wear. That was because Ni3P phaseformed for Ni–W–P alloy during the process of 400 1C heattreatment. During the wear–corrosion process, Ni3P phase wasmore easily removed which resulted in W atoms enrichment onthe surface of alloys.

EDS results of Ni–W–P alloy before and after worn in 3.5 wt%NaCl solution were shown in Table 5. For Ni–W–P alloy heattreated at 400 1C, just as in deionized water, phosphorus elementin alloy disappeared and the Ni/W atomic ratio increased aftercorrosive wear. Slight difference of O content was observed. The Oelement disappeared in deionized water after worn and 4% of Oelement was still preserved in 3.5 wt% NaCl solution. This meansthe slight wear loss happened in 3.5 wt% NaCl solution. Wear ratesalso confirmed this result. It was noted that for as-prepared Ni–W–P alloy, Fe and P elements were observed on alloy surface after

Table 2Corrosion rates of Ni–W–P alloys and Ni–P alloys in NaCl solution.

Sample As-preparedNi–W–P

200 1C treatedNi–W–P

300 1C treatedNi–W–P

400 1C treatedNi–W–P

500 1C treatedNi–W–P

600 1C treatedNi–W–P

As-preparedNi–P

400 1C treatedNi–P

Corrosion ratesmg/(cm2 h)

2.37E�04 6.05E�04 6.36E�04 1.11E�03 6.78E�04 7.26E�04 1.49E�03 9.31E�03

0 100 200 300 400 500 600

1

2

3

4

5

6

7

Wea

r R

ates

(mg/

h)

In deionized waterIn 3.5 wt.% NaCl solution

Fig. 6. Wear–corrosion rates of Ni–W–P alloys under different heat treatmenttemperature in deionized water and 3.5 wt% NaCl solution.

Table 3Wear rates of electroless plated Ni–P alloys in deionized water and 3.5 wt% NaClsolution.

Sample Hardness(HV)

Deionized waterwear rates (mg)

3.5 wt% NaCl solutionwear rates (mg)

As-prepared 552 38.075 61.9400 1C heat-

treated860 13 16.5

Time (sec)0 2000 4000 6000 8000

Fric

tion

coef

ficie

nt

0.0

0.2

0.4

0.6

0.8

1.0

400 heat-treated in deionized waterAs-prepared in deionized water400 heat-treated in 3.5 wt.% NaCl solutionAs-prepared in 3.5 wt.% NaCl solution

Fig. 7. The friction coefficient of Ni–W–P alloys as-prepared and 400 1C heat-treated in both deionized water and 3.5 wt% NaCl solution.

F.J. He et al. / Wear 311 (2014) 14–20 17

worn in 3.5 wt% NaCl solution. This may be caused by mildadhesive wear between alloy and GCr15 counter sample. Ironand nickel have a high mutual solubility [22], Fe atom transferredfrom the GCr15 steel ball surface to Ni–W–P alloy surface. The

appearances of O element after corrosive wear also indicated amild adhesive wear occurring.

As described above, in deionized water, the wear mechanismsof Ni–W–P alloys were abrasive wear, both in the as-prepared and

Fig. 8. Scanning electron micrograph of worn Ni–W–P alloy surface (a) as-prepared and (b) 400 1C heat-treated in deionized water, as-prepared (c, e) and 400 1C heat-treated (d, f) Ni–W–P alloys at different magnifications in 3.5 wt% NaCl solution; (g) worn surface of electress Ni–P alloy.

F.J. He et al. / Wear 311 (2014) 14–2018

heat-treated states; but in 3.5 wt% NaCl solution, it showed a mildadhesive wear mechanism in as-prepared state and abrasive wearin 400 1C heat-treated state. It is because that after 400 1C heattreatment the Ni4W phases and oxide formed. These secondphases increased the hardness of alloy and oxide at the surface,prevented direct contact of alloy with couple in wear process. Inthis case, the wear rate decreased and adhesive wear prevented.Compared with Ni, the second phases had a higher potential andhardness, which could accelerate the departure of Ni atoms. Onthe other hand, when the treatment temperature was higher than400 1C, the wear rate in 3.5 wt% NaCl solution became lower. ForNi–W–P alloy in as-prepared state, the main wear was caused bycorrosive wear; for the alloy in heat-treatment state, the mainwear was caused by abrasive wear. Following microcell reactionsmay happen.

Anode reactions

Ni-Ni2þþ2e�

Ni2þþH2O-NiOþ2Hþ

Pþ4H2O-PO3�4 þ8Hþþ5e�

2PO3�4 þ3Ni2þ-Ni3(PO4)2

Wþ3H2O-WO3þ6Hþþ6e�

Cathode reactions

2Hþþ2e�-H2

4.2. Quantitative estimation of the synergy effect

As pointed out by researchers, the corrosion–wear, in which thematerial was subjected to wear and corrosion simultaneously, wasnot simply the combined effect of both events. The synergy effectcould dominate the behavior of the material in corrosive environ-ment. The weight loss of the Ni–W–P alloy in corrosive wear

behavior can be expressed as following [23,24]:

W total ¼WwearþWcorrþΔW ð1Þwhere, Wtotal is the total weight loss in corrosive wear; Wwear isthe pure wear weight loss (in solution without corrosion); Wcorr isthe pure corrosion weight loss; ΔW is the synergy effect of wearand corrosion. So

ΔW ¼W total�Wwear�Wcorr ð2ÞThe synergy effect of corrosive wear behavior of Ni–W–P alloy

exposed 7 cm2 area in 3.5 wt% NaCl solution were calculatedaccording to Eq. (2) and results were shown in Table 6.

In 3.5 wt% NaCl corrosive solution, synergy effect of wear andcorrosion was observed. According to Table 6, the total wear lossand pure wear loss of Ni–W–P alloy in 400 1C heat-treated statewere lower than those of alloy in as-prepared state. The increasedhardness of Ni–W–P alloy caused by the precipitation of secondphases was responsible for its improved wear resistance. Wtotal

and Wwear were in the same order of magnitude. Wcorr were lowerthan Wtotal and Wwear three orders of magnitude. It meant that themechanical attack performed a predominant contribution to thetotal corrosive wear. The synergy effect of Ni–W–P alloy in 400 1Cheat-treated state was much lower than those in as-preparedstate. The ratios of ΔW/Wtotal of Ni–W–P alloy in heat-treated andas-prepared state were 20.15%, and 55.0%, respectively. While theratios of Wwear/Wtotal of Ni–W–P alloy in heat-treated and as-prepared state were 79.31%, and 44.44%, respectively. According toTable 3, the ratios of Wwear/Wtotal of Ni–P alloy in heat-treated andas-prepared state were 78.8%, and 61.5%, respectively. From theabove discussion it implied that the second phases of the alloyafter heat-treated made a major influence on synergy effect.

Synergistic attack of corrosion and wear can result in a higherrate of material removal. During corrosive wear, plastic deforma-tion makes the target surface more anodic and thus acceleratesmaterial dissolution [25]. In the process of 400 1C heat treatment,the precipitation of the second phases Ni4W increased the hard-ness of Ni–W–P alloy. The higher hardness of alloy heat-treated at400 1C resulted in a larger resistance to mechanical plowing in thecorrosive environment, while the softer as-prepared alloy had alower resistance to plowing which could make the alloy moreanodic and thus a higher synergy effect.

Usually the loss caused by combined action of corrosion andwear, when a passive metal or alloy is subjected to sliding wear ina corrosive environment, the total material removal rate differsfrom that predicted by simply adding the wear rate measured inthe absence of corrosion and the corrosion rate observed in theabsence of wear. A good review of experimental observationsof the synergy effects between mechanical and chemical metal

Table 4EDS analysis of Ni–W–P alloy worn surface in deionized water.

Sample The element content beforewear (at%)

The element contentafter wear (at%)

Ni W P O Fe Ni W P O Fe

As-prepared 81.82 11.61 6.56 – – 91.51 8.49 – – –

400 1C heat-treated 83.08 8.34 2.67 5.07 – 86.44 13.56 – – –

Table 5EDS analysis of Ni–W–P alloy worn surface in 3.5 wt% NaCl solution.

Sample The element content before wear (at%) The element content after wear (at%)

Ni W P O Fe Ni W P O Fe

As-prepared 81.82 11.61 6.56 – – 84.22 8.51 1.24 2.54 3.48400 1C heat-treated 83.08 8.34 2.67 5.07 – 79.76 16.24 – 4.00 –

Table 6The synergy effect of Ni–W–P alloy as-prepared and heat-treated in 3.5 wt% NaCl solution.

Sample Wtotal (mg/h) Wwear (mg/h) Wcorr (mg/h) ΔW (mg/h) ΔW/Wtotal Wwear/Wtotal (%) Wcorr/Wtotal

As-prepared 3.15 1.4 1.66E�03 1.7 55.50% 44.44 5.27E�04400 1C heat-treated 1.45 1.15 7.77E�03 0.29 20.15% 79.31 5.36E�03

F.J. He et al. / Wear 311 (2014) 14–20 19

removal has been observed. The synergy effects play an importantrole in attacking many industrial facilities when exposed to acorrosive environment. As for Ni–W–P alloy sliding wear in acorrosive environment also follows the same general rules ofcorrosion–wear behavior. That is the higher hardness of materialsresult in a lower synergy effect and a larger resistance tomechanical plowing, when sliding wear in the corrosive environ-ment. It is a better way to increase the hardness of materials usedin industry to improve the performance of engineering materialswhen working in a corrosive environment.

5. Conclusions

(1). The main wear mechanism for Ni–W–P alloy in deionizedwater, both as-prepared and as-heat-treated, was abrasion.The heat-treated alloy had the least wear in deionized water.

(2). Corrosion and adhesive wear were the main surface damagemechanisms for the as-prepared alloy in 3.5 wt% NaCl solu-tion. For the heat-treated alloy, primarily abrasion with acontribution from corrosion resulted in surface damage.

(3). Corrosion–wear effects were prominent for both as-preparedand heat-treated Ni–W–P when tested in the saline solution.The mechanical contribution to wear was predominant.Second phases in the alloy, which raised its hardness, had amajor influence on wear–corrosion synergy. After heat-treat-ment, the synergism seemed to be less important in wearresponse than it was in the as-prepared condition.

Acknowledgments

Financial support for this work by the “11th five-year” NationalScience and Technology Support Program of China (No. 2006BAE-03B04) and the Hunan Nanofilm New Material Technology Co.Ltd.. isgratefully acknowledged.

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