Structural and phase transformation behaviour of electroless Ni-W-Cr-P alloy coatings on stainless steel

Article abstract of DOI:10.1134/S0020168510060130

Ni-W-Cr-P alloy coatings were prepared by electroless deposition on stainless steel. The effects of heat-treatment on the structure and phase transformation behavior, microhardness of the Ni-W-Cr-P alloy coatings were mainly investigated. XRD analysis sho

Full text of DOI:10.1134/S0020168510060130

ISSN 0020ꢀ1685, Inorganic Materials, 2010, Vol. 46, No. 6, pp. 631–638. © Pleiades Publishing, Ltd., 2010.
Structural and Phase Transformation Behaviour of Electroless
Ni–W–Cr–P Alloy Coatings on Stainless Steel
Yong Jin, Jing Fan, Ke Mou, Xuejuan Wang, Qun Ding, Yuan Li, and Chunmei Liu
Department of Materials Science, Sichuan University, Chengdu 610064, China
eꢀmail: yongjinꢀscu@163.com
Received April 29, 2009
Abstract—Ni
of heatꢀtreatment on the structure and phase transformation behavior, microhardness of the Ni–W–Cr–P
alloy coatings were mainly investigated. XRD analysis shows that asꢀdeposited Ni–W–Cr–P coatings were
microcrystalline; the precipitation of Ni3P was observed at the annealing temperature of 400 ; after heatꢀ
treatment at 500 the crystallization of Ni3P and Ni was near completion; at 600 new phase Cr1.12Ni2 .88
was observed and Ni3P began to decompose. Cr1.07Fe18.93 and Ni17W3 were formed when heated at 700
and Ni3P was not found. With increasing temperature to 800 C, FeNi2P and Cr4Ni15W were the only two
dominant phases. The experimental results reveal that with an increase in the annealing temperature, microꢀ
hardness of the Ni–W–Cr–P alloy coatings increased, reached the maximum value at 700 , and then
−W
−
Cr P alloy coatings were prepared by electroless deposition on stainless steel. The effects
−
°
C
°
C
°C
°C,
°
°
C
decreased slightly. Annealing temperature dependence of the microhardness and corrosion resistance of the
coatings was also observed. The related strengthening mechanism in the electroless deposited Ni–W–Cr–P
alloy coatings is also discussed.
DOI: 10.1134/S0020168510060130
1
INTRODUCTION
resistance of the alloy coatings with proper annealing
temperature was also discussed.
Stainless steel is widely used in various industries
due to its excellent properties. While, with low hardꢀ
ness and poor wear resistance, corrosion process of
stainless steel will accelerate when micro scratch occur
on the surface followed by the formation of microcell.
As a convenient surface treatment technique, electroꢀ
less Ni–P plating is a very effective method to improve
the properties of stainless steel due to its excellent hardꢀ
ness, wear resistance and corrosion resistance [1–3].
EXPERIMENTAL
Stainless steel (20 mm × 20 mm × 1 mm) was used
as substrate. The surface of stainless steel is easily pasꢀ
sivated, thus is harmful for electroless plating. There
are two main factors contributed to this: elevated elecꢀ
trode potential and poor adhesion between the subꢀ
strate and the plating. Then, prior to plating, the samꢀ
ples were subjected to shot blast treatment to obtain
clean and fresh surface with proper roughness. Then
the samples were degreased in hot alkaline solution for
10 min, rinsed in running water and deionized water.
The degreased samples were deoxidized in dilute
hydrochloric acid solution for 2 min, rinsed in running
water and deionized water. Finally, the samples were
immediately immersed in the electroless plating soluꢀ
tion for deposition. Ni–W–Cr–P alloy coatings were
prepared by altering the chemistry solution with
proper ratio of A : B solution. The pH value of the platꢀ
ing bath was adjusted with ammonia and 30% acetic
acid to 8.8–9.2, and the plating time was 2 h at a bath
Many investigations have been reported on introꢀ
duction of W or Cr into the binary electroless Ni–P
deposit to form ternary Ni–W–P, Ni–Cr–P alloy
coatings to further enhance the deposit properties
because of their high melting temperature and unusual
mechanical properties [4–14]. However, to date there
are few reports on the preparation of the quaternary
Ni–W–Cr–P alloy coatings by electroless deposition.
In the present study, the quaternary Ni–W–Cr–P
alloy coatings were prepared by introduction of Cr into
electroless Ni–W–P deposits. The effects of the
annealing temperature on the crystal structure, microꢀ
hardness, and corrosion resistance of Ni–W–Cr–P
alloy coatings were mainly studied. The related mechꢀ
anism for enhanced microhardness and corrosion
temperature of 85–90 C. The compositions of the
°
bath and the operating conditions for Ni–W–Cr–P
alloy coatings are shown in Table 1. After plating,
1
The article is published in the original.
631

632
YONG JIN et al.
Table 1. Composition and operating conditions of the electroless Ni–W–Cr–P bath
Chemical compounds A
Concentration
Chemical compounds B
Concentration
NiSO4
⋅
6H2O
2H2O
2H2O
30–40 g/L
25–30 g/L
80–100 g/L
40–60 g/L
10–20 g/L
10–20 ml/L
10–30 mg/L
8.8–9.2
⋅
10–15 g/L
10–20 g/L
4–6 g/L
CrCl3 6H2O
NaH2PO4 H2O
K2C2O4 H2O
Na2WO4
⋅
⋅
Na3C6H5O7
NH4Cl
⋅
⋅
NaC2H3O2
10–20 g/L
NaH2PO2
⋅
H2O
NH3 ⋅ H2O
Stability
pH
Stability
10–20 mg/L
4–6
again the sample was rinsed in running water and
deionized water, dried and preserved for characterizaꢀ
tion.
The polarization curves of the alloy coatings were
measured using Autolab PG302 Potentiostat Electroꢀ
chemistry Workstation.
To investigate the effects of heat treatment at temꢀ
RESULTS AND DISCUSSION
peratures ranging from 300 to 800 C on the structure
°
and hardness of the deposits, annealing was carried out
in a tube resistance furnace with N2 purged for 1 h and
the sample was then furnaceꢀcooled to room temperꢀ
ature.
Elemental composition and SEM analysis of elecꢀ
troless Ni–W–Cr–P alloy coatings. The compositions
of asꢀplated electroless Ni–W–Cr–P coatings with
different ratio of A solution to B analyzed by Xꢀray fluꢀ
orescent spectrometer (Rigaku Xꢀray Fluorescence
ZSX100e) are listed in Table 2.
Elemental compositions of the deposits were deterꢀ
mined with an Xꢀray fluorescent spectrometer. Scanꢀ
ning electron microscope (SEM, JSEꢀ5900LV) was
employed to study the surface morphology as well as
crossꢀsection of the deposit in asꢀplated condition.
Figure 1 shows SEM image of the surface of Ni–
W–Cr–P deposit in asꢀplated condition prepared
with the ratios of A solution to B as 1 : 1. The surface
morphology of the deposit is homogeneous and comꢀ
pact. The quaternary Ni–W–Cr–P alloy deposit
exhibited nodular structure. The particles are of differꢀ
ent sizes, irregularly cellular. The deposit thickness
The structures of the Ni–W–Cr–P deposits both
in asꢀplated and heatꢀtreated conditions were evaluꢀ
ated with an Xꢀray diffractometer (DXꢀ1000, Danꢀ
was around 10 m through SEM analysis of the crossꢀ
μ
dong, China) using Cu
K radiation. The chemical
α
section of the deposit as shown in Fig. 2.
composition of the layers was measured by Rigaku
Xꢀray Fluorescence ZSX100e.
Phase transformation behavior of electroless
Ni–W–Cr–P alloy coatings. Figures 3–10 shows the
Xꢀray diffraction patterns of the Ni–W–Cr–P quaterꢀ
nary alloy coatings in asꢀplated condition and heated
at various temperatures for 1 h.
Microhardness measurements were done using a
HV2100 microhardness tester. Five readings were
taken on each deposit and the values were then averꢀ
aged.
Figure 3 show the XRD patterns of substrate (stainꢀ
less steel) and asꢀdeposited Ni–W–Cr–P alloy coatꢀ
ings without annealing temperature, respectively. As
Table 2. Compositions of asꢀdeposited Ni–W–Cr–P alloy
coatings with different ratios of A to B
shown in Fig. 3 (curve
2), there is a noncrystal peak at
2θ
= 45°. So it was thought that the asdeposited alloy
A : B
Ni, wt % P, wt %
W, wt % Cr, wt %
coatings belong to amorphous structure. There is no
obvious change in the diffraction pattern of the deposit
4 : 6
5 : 5
6 : 4
7 : 3
8 : 2
87.1
86.6
86.6
86.6
86.9
5.6
5.2
5.0
4.8
4.6
4.1
5.2
5.7
6.1
6.2
3.2
3.0
2.7
2.5
2.3
heated at 300 C, as shown in Fig. 4. In Ni–W–Cr–P
°
system, the original amorphous structure was transꢀ
formed into a mixture of amorphous, Ni and Ni3P
crystallites at 400°C as shown in Fig. 5. It could also be
found that the deposit started to gave rise to precipitaꢀ
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STRUCTURAL AND PHASE TRANSFORMATION BEHAVIOUR OF ELECTROLESS
633
10 μm
10
μ
m
Fig. 1. SEM image of surface morphology of asꢀplated
Fig. 2. SEM image of crossꢀsection of asꢀplated electroless
Ni–W–Cr–P alloy coating (×2000).
electroless Ni–W–Cr–P alloy coating (
×
2000).
3000
2500
2000
1500
1000
500
0
2
1
33ꢀ0397 > FeCr0.29Ni0.16CO.06 P Austenite
30
40
50
60
70
2θ, deg
Fig. 3. XRD patterns of the stainless steel substrate.
tion of fine Ni3P grains. From Fig. 6, it is evident that at 800°C consisted of FeNi2P and Cr4Ni15W phases
(Fig. 9).
after annealed at 500 C, reflections of both Ni3P and
°
Ni phases were further sharpened into wellꢀdefined
diffraction peaks, which indicates that crystallization
process of N3P and Ni was near completion. As is
shown in Fig. 7, diffraction peaks of Cr1.12Ni2.88 was
observed and the intensity of diffraction peaks of Ni3P
decreased which means it began to decompose after
Microhardness of electroless Ni–W–Cr–P alloy
coating. The effects of heat treatment on the hardness
of electroless Ni–W–Cr–P alloy coatings was studied.
Figure 10 shows that with a microhardness of
574HV in asꢀdeposited condition, hardness of the
quaternary Ni–W–Cr–P alloy coatings increased
with the increasing annealing temperature, until
reached the maximum value of 964HV when heated at
annealed at 600°C. With increasing temperature to
700 , the diffraction refection indicates that N3P
°C
completely disappeared, and new phases of
Cr1.07Fe18.93 and Ni17W3 were the only two dominant
700
°
C
for 1 h. Then it slightly decreased after heated at
. According to the analysis of phase transformaꢀ
800°
C
phases, as shown in Fig. 8. The alloy coatings annealed tion behaviors of the deposits above, it can be conꢀ
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634
YONG JIN et al.
5000
4000
3000
2000
300°C annealed
2
1
1000
0
asꢀdeposited
70
30
40
50
60
2θ, deg
Fig. 4. XRD pattern of the Ni–W–Cr–P alloy coating annealed at 300°C for 1 h.
6000
5000
4000
3000
2000
1000
0
34ꢀ0501 > Ni3P – Nickel Phosphide
65ꢀ2865 > Ni – Nickel
30
40
50
60
70
2θ
, deg
Fig. 5. XRD pattern of the Ni–W–Cr–P alloy coating annealed at 400°C for 1 h.
cluded that after annealing above 300 C, the enhanced phases Cr1.07Fe18.93 and Ni17W3 the hardening mechaꢀ
°
hardness has been mainly attributed to the increase in
the number of fine Ni microcrystallites. Precipitation
hardening of fine Ni3P crystallites is responsible for the
nism of which need to be further investigated. With
increasing temperature to 800 , hardness decreased
while still remained a relatively high value of 804HV.
°C
considerable increase in hardness at 400
heatꢀtreatment at 500 , in spite of the growth of Ni
and Ni3P particles the hardness of the deposit continue
to increase. After heated above 600 C, Ni3P started to
decompose, but the hardness of the deposit did not
decrease until at 800 . Slight increase in hardness at
600 and 700 C may be a result of the formation of new corrosion resistance of Ni–W–Cr–P alloy coatings, asꢀ
°C. After the
The incorporation of Cr in Ni–W–P deposit make
the phase transformation behavior more complex, and
the formation of various kinds of intermetallic comꢀ
pounds impede the decrease in the hardness.
°C
°
Corrosion resistance of electroless deposited
Ni–W–Cr–P alloy coating. In order to evaluate the
°C
°
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STRUCTURAL AND PHASE TRANSFORMATION BEHAVIOUR OF ELECTROLESS
635
14
12
10
8
6
4
2
×
103
34ꢀ0501 > Ni3P – Nickel Phosphide
65ꢀ2865 > Ni – Nickel
30
40
50
60
70
2θ, deg
Fig. 6. XRD pattern of the Ni–W–Cr–P alloy coating annealed at 500
°
C
for 1 h.
6000
4000
2000
0
34ꢀ0501 > Ni3P – Nickel Phosphide
65ꢀ5559 > Cr1.12Ni2.88 – Chromium Nickel
30
40
50
60
70
2θ, deg
Fig. 7. XRD pattern of the Ni–W–Cr–P alloy coating annealed at 600°C for 1 h.
deposited (i.e., without annealing) Ni–P, Ni–W–P, NaCl, 10% HCl and 10% H2SO4 for 12 days, respecꢀ
and Ni–W–Cr–P alloy coatings with the same thickꢀ
nesses were put into the solution of 10% NaOH, 5%
tively. Corrosion rate of these alloy coatings is calcuꢀ
lated by weight method. Detailed results were shown
Table 3. Microhardness of Ni
−
W−
Cr−P alloy coatings heated at different temperatures
Asꢀdeposited coatings
10% NaOH
5% NaCl
10% HCl
10% H2SO4
Ni–P
1.33
1.22
1.10
1.14
0.11
0.07
330
300
260
70
42
26
Ni–W–P
Ni–W–Cr–P
INORGANIC MATERIALS Vol. 46
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636
YONG JIN et al.
1000
750
500
250
0
65ꢀ4828 > Ni17W3 – Nickel Tungsten
65ꢀ7775 > Cr1.07Fe18.93 – Chromium Iron
30
40
50
60
70
2θ, deg
Fig. 8. XRD pattern of the Ni–W–Cr–P alloy coating annealed at 700°C for 1 h.
1500
1000
500
0
65ꢀ5108 > Cr4Ni15W – Chromium Nickel Tungsten
51ꢀ1367 > FeNi2P – Iron Nickel Phosphide
30
40
50
60
70
2θ, deg
Fig. 9. XRD pattern of the Ni–W–Cr–P alloy coating annealed at 800°C for 1 h.
in Table 3. It was found from Table 3 that the corrosion coatings in different mediums, especially for 10%
resistance of asꢀdeposited Ni–W–Cr–P alloy coatꢀ H2SO4. The Ni–W–Cr–P alloy coatings is still bright
ings shows better than those of Ni–P and Ni–W–P
except for 10% NaOH solution. As a result, the asꢀ
Table 4. Corrosion rate of asꢀdeposited coatings in different mediums (mg/(d cm2))
Annealing temperature,
Microhardness (HV)
°
C
25
300
673
400
825
500
908
600
928
700
964
800
804
574
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STRUCTURAL AND PHASE TRANSFORMATION BEHAVIOUR OF ELECTROLESS
637
CONCLUSIONS
B
1000
950
900
850
800
750
700
650
600
550
In the present study, the Ni–W–Cr–P alloy coatꢀ
ings were prepared by electroless deposition.
After shot blast treatment, a clean and fresh surface
with proper roughness of the stainless steel substrate
was obtained.
Heatꢀtreatment has a significant effect on the
structure of the Ni–W–Cr–P alloy coatings. Asꢀ
deposited Ni–W–Cr–P alloy coatings were microcꢀ
rystalline; the precipitation of Ni3P was observed at the
annealing temperature of 400
at 500 the crystallization of Ni3P and Ni was near
completion. At 600 new phase Cr1.12Ni2.88 was
observed and Ni3P began to decompose. Cr1.07Fe18.93
and Ni17W3 were formed when heated at 700 , and
Ni3P was not found. With increasing temperature to
800 C, FeNi2P and Cr4Ni15W were the only two domiꢀ
nant phases.
The hardness of electroless Ni–W–Cr–P alloy
°C; after heatꢀtreatment
°C
°C
0
200
400
Heating temperature,
600
800
°
C
°C
Fig. 10. Microhardness of the Ni–W–Cr–P alloy coatings
at different annealing temperatures for 1 h.
°
100
101
102
103
104
coatings increased with the increasing annealing temꢀ
perature, reached the maximum value of 964HV when
heated at 700
at 800 , but still remained a relatively high value of
804HV.
°C for 1 h. Then it decreased after heated
°C
The Ni–W–Cr–P alloy coatings were more corroꢀ
sion resistant than Ni–P and Ni–W–P alloy coatings
in asꢀdeposited condition in 10% H2SO4 medium.
105
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