Materials Express

Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy

Wei Lan∗, Shuai Zhao, and Wen Zhou

School of Metallurgy and Materials Engineering, Chongqing University Science and Technology, Chongqing 401331, China

ABSTRACT Nanocrystalline Fe was obtained from the surface of low carbon steel by shot peening technology and nanocrystalline Fe–Ni alloy was obtained from the surface by electroplating nickel. A series of diffusion layers of nanocrystalline Fe–Ni alloy were prepared by controlling the temperature during heat treatment. The micro-morphology and interface composition was observed by scanning electron microscopy and X-ray diffraction. The nanocrys- Article talline Fe–Ni alloy corrosion resistance was evaluated by electrochemical workstation. The results show that with the increase of shot peeningIP: 192.168.39.210 time, the iron On: grain Mon, size 27 decreased,Sep 2021 07:01:00 the smallest grain size reached was 256 nm. According to the analysisCopyright: of error function, American the Scientific inter-diffusion Publishers coefficient of Fe–Ni alloy increases with Delivered by Ingenta increasing diffusion temperature. When heat treatment temperature reaches 923 K, the diffusion layer thickness is 18.59 m, the diffusion coefficient of Ni in Fe is 9.36 × 10−16 m2/s. The diffusion model of nanocrystalline Fe–Ni plating layer is obtained by the Boltzmann-Matano method. It is found that the corrosion potential and the corrosion current density at a temperature of 923 K are −0.4379 V and 2.145 × 10−6 A/m2, respectively, and the corrosion resistance of the plating increases with increasing temperature. Keywords: Nanocrystalline, Fe–Ni Alloy, Diffusion Coefficient, Boltzmann-Matano Method, Electrochemistry, Corrosion.

1. INTRODUCTION resistance, and high temperature oxidation resistance, and The preparation of nano-particles has attracted increasing is thus widely used in manufacturing. 4 attention due to their unique physical and chemical prop- There are multiple ways to prepare nanocrystalline erties. Nano iron, cobalt, nickel and its alloys are widely alloys. Valderrunten 5 used high-energy milling and used in national defense, medicine, metallurgy, electron- nanotechnology methods of preparation that allowed ics, chemical environmental protection, and other ﬁelds.1 powdered samples with different structures and novel This interest is especially so in the ﬁeld of oil exploita- properties to be obtained. Some experts have adopted a tion, as deep well development leads to a rise in temper- mechanical treatment method, which makes the surface of

ature and pressure, and increased CO2,H2S, and chloride the material plastically deformed so that grain reﬁnement 2 ion concentrations. In humid H2SandCO2 environments, is achieved. These mechanical treatment methods include metal materials can suffer severe corrosion, resulting in dif- ultrasonic mechanical vibration technology, ultrasonic shot ferent types of corrosion in different parts of the downhole peening technology, mechanical grinding, surface rolling, casing. To prevent accidents due to this corrosion, corrosion and laser peening. 6 7 The Chinese Academy of Sciences resistant metals are needed.3 Nickel-based alloys have Luke research group used the surface mechanical grind- excellent resistance to erosion, wear resistance, corrosion ing method, in a variety of engineering materials carried out in-depth surface from the nano-research, such as pure ∗Author to whom correspondence should be addressed. iron, 316 L stainless steel, aluminum, titanium, low carbon Email: [email protected] steel, copper among other studies. 8–11

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Ni-based alloying of low-carbon steel is achieved 2.3. Heat Treatment through surface alloying. According to reports in the lit- According to the Fe–Ni two-phase diagram, three kinds erature, the current method of surface alloying of metallic of temperature 723 K, 823 K and 923 K were selected. materials adopts surface metallurgy methods. That is, by This experiment chose a box resistance furnace. The sam- using high density energy on the surface of the material, ple was heated in the box type resistance furnace to the the surface layer melts, and the alloy is made in the molten temperature specified in the experiment, the sample kept pool. Sergey Zherebtsov produced a new alloy. The alloy- in the box type resistance furnace for 10 h, and finally ing was produced by melting pre-deposited Al–Si pow- cooled with the furnace. der and a portion of underlying substrate with a pulsed Nd:YAG laser beam. The microhardness of the modi- 2.4. Electrochemical fied layer was found to be 2.5 times higher than that of Electrochemical tests were carried out in a conventional untreated steel. The erosion test of the laser alloyed surface three electrode system using a PARSTAT P4000 elec- and steel in mercury was carried out by using an electro- trochemical workstation. Experiments were conducted at magnetic impact testing machine. The laser alloyed surface ambient temperature (293 ± 2 K), and at atmospheric was found to be less damaged after 105 cycles of impacts pressure. For the room temperature electrochemical mea- compared to untreated stainless steel. 12 Rotshtein chose surements, a conventional three-electrode configuration Cu to sputter onto a 316 stainless steel substrate to form a including a KCl-saturated Ag/AgCl reference electrode layer of Cu film in the microwave discharge of the plasma (200 mV SHE) and one Pt counter electrode were used. environment, they used low energy (20–30 keV) and high For each test a new specimen and freshly prepared test current pulsed electron beam (2–3 s, 2.8–8.4 J/cm) on solutions were used. L-shaped specimens with a measur- the Cu film and matrix metal system melting and alloying ing surface of ca. 100 mm2 were cut by wire electri- treatment, surface formed in a 120–170 m alloy diffusion cal discharge machining from bars along the longitudinal layer. 13 Reference [14] demonstrated that there is a tran- plane. Prior to the electrochemical tests, the surface of the sition layer between the nano-layer on the surface and the samples was treated by mechanical grinding consecutively coarse grain region inside. There are some surface treat- with SiC emery papers up to 360 grit prior to each exper- ment techniques, such as plasma arc welding, 15 thermal iment. The open circuit potential (OCP) and polarization spraying,16 laser cladding17–19IP:among 192.168.39.210 others, which On: have Mon,curves 27 Sep for 2021 the 07:01:00 specimens were measured in 3.5% NaCl Copyright: American Scientific Publishers been widely used in the preparation of nickel-basedDelivered alloy by Ingentasolution (pH 6.7, open to air). After immersion in the solu- coatings to improve the performance of the metal matrix. tion for 1 hour, the polarization curves were obtained by In this paper, we used shot peening to prepare micro- scanning the potential from −0.25 V versus the OCP to

Article nanocrystalline iron on the surface of low carbon steel. 0.25 V versus the OCP for every specimen and sweep rate After the shot peening, nickel electroplating is performed of 0.167 mV/s. on the surface of nanocrystalline iron, and micro-nano iron-nickel alloy materials were obtained. The inﬂuence of 2.5. Neutral Salt Spray Test different temperatures on the diffusion behavior and corro- Neutral salt spray tests were carried out in salt spray test sion resistance of the nanometer Fe–Ni alloy plating layer chamber. The laboratory ambient temperature is 296±2K. was investigated. XRD and SEM were used to analyze The temperature in the test chamber is 309 ± 0.1∼0.7 K. the phase and morphology of the nanometer Fe–Ni alloy The concentration of saline solution is (5±1)% NaCl solu- plated layer, and the corrosion resistance was evaluated by tion. Settling salt solution pH is 6.5–7.2. The sample is electrochemical workstation. placed at an angle of 30 from the vertical plane. The spray method is continuous spray. The spray time is 24 hours. 2. EXPERIMENTAL DETAILS 2.1. Shot Peening 3. RESULTS AND DISCUSSION We used shot peening to prepare nanocrystalline iron on 3.1. X-ray Diffraction the surface of low carbon steel. The experiment was car- 3.1.1. Effect of Shot Time ried out on a shot blasting machine, the constant pressure Figure 1 shows the XRD spectra of different shot peen- was 0.3 MPa, steel ball size was 0.3 mm, and the shot ing times for nanocrystalline Fe–Ni alloys. It can be seen peening times were 5 min, 10 min and 15 min. that the diffraction peak has shifted to a small angle as the shot peening time increases. As can be seen in Figure 1(b), 2.2. X-ray Diffraction for samples that have not been shot peened, the span of The X-ray diffraction experiments used the DX-2700 the strongest peak is 0.6, while when the shot peening instrument and the diffraction used Cu K radiation. The time is 5 min, the span of the strongest peak is 1.3.The tube voltage was 35 kV, the tube current was 25 mA, the experimental results show that the grain size of the sam- scanning mode is step-by-step scanning, the step width is ple becomes smaller with the increase of shot peening 0.05, step time is 1 sec, and the diffraction angle is 30–90. time.

246 Mater. Express, Vol. 8, 2018 Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy Materials Express Lan et al.

(a) (b) (111) (111) (200) (220) (200) 15 min 15 min

10 min 10 min

5 min 5 min

0 min 0 min

30 40 50 60 70 80 90 40 50 2θ 2θ

Fig. 1. (a) XRD spectra, (b) local XRD spectra. X-ray diffraction (XRD) spectra of species on the nanocrystalline Fe–Ni alloys surface with different shot peening times.

According to the Scherrer formula,20 21 their average At an experimental temperature of 723 K, we found that particle size is determined by the formula (1). FeNi compounds are present in the sample. This is because Ni atoms and Fe atoms form a supersaturated solid solution k D = (1) when the Ni atoms diffuse into the iron interface. Atoms B cos K K = B where is the Scherrer constant, 0.89; is the half Article width of the diffraction peak, rad; D is the average thick- NiO ness of the crystal grains perpendicular to the crystal plane, Ni IP: 192.168.39.210 On: Mon, 27 Sep 2021Δ 07:01:00 Δ FeNi nm; is the diffraction angle, rad; Copyright:is the X-ray American wave- Scientific Publishers length, 0.154056 nm. According to Eq. (1), we canDelivered calcu- by Ingenta 923 K late the sample’s average particle size, as shown in Table I.

823 K 3.1.2. Effect of Temperature Fe and Ni belong to the same family of elements and have the same electronic layer structure. The Fe–Ni alloy phase diagram is a typical homogeneous phase diagram, and the 723 K two groups of elements are not only infinitely soluble in the liquid state, but also infinitely soluble in the solid state. 293 K Different temperatures have been chosen to study the diffusion coefficient between Fe–Ni. For example, Danilchenko 30 40 50 60 70 80 90 100 θ and colleagues22 studied diffusion coefficients of Fe–Ni 2 at temperatures of 673 K and above 1193 K. Ugaste and Fig. 2. Product of different heat treatment temperatures. colleagues23 studied the concentration distributions of the components in the six diffusional couplings of the system determined at 1273 K for the conventional and effective inter-diffusion coefficients in the Cu–Fe-system. We deter- mine the temperatures to be used in this study: 723 K, 823 K and 923 K, from the literature and the Fe–Ni phase diagram. Afterselecting the shot peening time, the heat treatment experiments are conducted with temperatures of 723 K, 823 K and 923 K. XRD experiments were carried out to obtain the alloy’s composition as shown in Figure 2.

Table I. Grain sizes of samples after different shot peening times.

T /min 0 5 10 15 Fig. 3. Fe/Ni original interface (293 K, no heat treatment d/nm 624 495 459 256 experiment).

Mater. Express, Vol. 8, 2018 247 Materials Express Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy Lan et al.

Fig. 4. (a) 723 K, (b) 823 K, (c) 923 K. Fe–Ni interface after different heat treatment temperature.

at the interface have high activity, strong distortion, and The left side of the interface is Fe, the right side is easy generation of intermetallic compounds.24 As the heat Ni, and they are in close contact. Due to the relatively treatment temperature increases, FeNi compounds increase, high hardness of Ni, it is easy to make a rivet with a and FeNi peaks also broaden. When the temperature was smooth surface. After being embedded in the Fe, the two more than 823 K, a new product (NiO) was produced. phases are dense and the interface is smooth and very clear. 3.2. Diffusion Microscopic Morphology From the phase diagram of the Fe–Ni binary alloy, it An image of the interface micro-morphology of a sam- can be seen that the inter-diffusion between fully dissolved ple that has not been heat-treated, is shown in Figure 3. solid solutions is dominated by displacement diffusion, IP: 192.168.39.210 On: Mon, 27 Sep 2021 07:01:00 (a)Copyright: American Scientific (b) Publishers 100 Delivered by Ingenta100 Fe Fe 80 80

Article 60 60

40 40 content/% content/%

20 20 Ni Ni 0 0

0 10203040506070 0 1020304050 x/μm x/μm (c) 100 Fe

40 content/%

Ni 0

0 102030405060 x/μm

Fig. 5. (a) 723 K, (b) 823 K, (c) 923 K. Distribution curves of Fe–Ni concentration after different heat treatments.

248 Mater. Express, Vol. 8, 2018 Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy Materials Express Lan et al.

Table II. The diffusion coefficient of different positions at different the diffusion layer. The thickness of the diffusion layers heat treatment temperatures (m2/s × 10−12. at 723 K, 823 K and 923 K were 3.51 m, 8.55 mand Diffusion distance 18.59 m, respectively. The relationship between the concentration of the dif- Temperature (K) 0.5 5.02 8.79 10.04 15.07 fusate and the time and the spatial position in the diffu- 723 0.0763 – – – – sion process is given by Fick’s Second Law (the Diffusion 823 0.0419 17991 54544 – – Second Equation). The Boltzmann-Matano model is 923 0.0541 2611 117631 13.4120 18.965 derived from Fick’s Second Law. The formula is as follows: C/t = /xDC/x√ , Boltzman transformations, order = x/ t, and the result of long-term inter-diffusion leads to interfa- cial migration. dC d dC − =− D (2) Figure 4 shows that there is no new intermetallic 2 d d d compound in the FeNi diffusion layer, and the mutual dif- Thus, the solution to the diffusion problem requires solv- fusion of Fe atoms and Ni atoms creates a solid solu- ing the partial differential equation given for the initial and tion at the interface. From the aspect of the size of the boundary conditions. This experiment takes the concentra- atom, if the difference in the atomic sizes of the compo- tion curve of Fe as the research object. It is assumed that nents in the solid solution is larger, the required deforma- there is no Fe in the plating before the heat treatment exper- tion energy is also larger. Also, the farther the solute atoms iment. We used the pre-diffusion interface as the origin of are from the deformation location, the easier the atoms the coordinates, with the plating layer direction as the pos- will diffuse. This is because the activation energy required itive x-axis, then the initial conditions are as follows. for atom diffusion is small. Fe atoms and Ni atoms are similar in size, thus they are C x < 0 Cx = 1 easier to form through the interface diffusion solid solu- 0 (3) C x ≥ 0 tion structure. As can be seen in Figure 4(a), there is a 2 Article clear interface between the Fe–Ni surfaces at 723 K, thus The formula (2) is integrated, indicating that there is no solidIP: solution 192.168.39.210 in the interface. On: Mon, 27 Sep 2021 07:01:00 C C It is apparent that the microstructureCopyright: of Fe and American Ni is not Scientific Publishers dC Delivered by Ingenta − dC = D (4) C d the same, and the small particles of Fe will diffuse into Ni. 1 2 C 1 The diffusion area in Figure 4 is marked. Thus, it can be due to dC/dC=C = dC/dx=− = 0, the formula (4) seen that with an increase in temperature, the Fe–Ni inter- 1 face becomes more blurred, and the diffusion area widens. is simplified to, This is due to the increase of temperature which promotes 1 C dC − dC = D (5) the diffusion of Fe atoms and Ni atoms. Therefore, a large C d 2 1 C amount of solid solution forms at the interface, and the √ presence of solid solution makes the interface blurred. and because at any moment, = x/ t the formula (5) is changed to 1 C dC 3.3. Diffusion Coefficient − xdC = D (6) t C d With the increasing temperature, the nickel concentration 2 1 C decreases gradually (the trend of increasing Fe concentra- Due to dC/dxC=C = 0, the formula (6) must be satisfied, 2 tion also becomes gentle) as shown in Figure 5. The results C 2 show that there is a material exchange between Fe and xdC = 0(7) C Ni, and the higher the diffusion temperature, the thicker 1

Table III. The relationship between temperature and various coefﬁcients (T = K − 273).

The relationship with The relationship with The relationship with Parameters temperature Parameters temperature Parameters temperature a1 a1 = 0.0034T 2 − 3.4942T + 915.49 b1 b1 = 0.00003T 2 + 0.14T − 51.751 c1 c1 = 0.00042 − 0.3699T + 88.669 a2 a2 =−0.0066T 2 + 6.7258T − 1587.9 b2 b2 =−0.017T 2 + 1.6685T − 355.99 c2 c2 = 0.001T 2 + 0.9431T − 194.38 a3 a3 = 0.0023T 2 − 2.7092T + 799.5 b3 b3 =−0.0002T 2 + 0.2919T − 89.195 c3 c3 = 0.00005T 2 − 0.06T + 18.24 a4 a4 =−0.0005T 2 + 0.3934T − 45.097 b4 b4 = 0.0018T 2 − 1.9377T − 545.73 c4 c4 = 0.0006T 2 − 0.7108T + 209.26 a5 a5 = 0.0006T 2 − 0.6564T + 166.65 b5 b5 = 0.0005T 2 + 0.4665T − 66.121 c5 c5 = 0.0002T 2 − 0.1907T + 48.338 a6 a6 = 0.003T 2 − 3.5093T + 1022.7 b6 b6 =−0.0004T 2 + 0.5364T − 146.44 c6 c6 = 0.0002T 2 − 0.2089T + 55.871 a7 a7 =−0.0005T 2 + 0.8009T − 224.37 b7 b7 = .0002T 2 − 0.1773T − 70.148 c7 c7 = 0.0003T 2 − 0.3472T + 95.699 a8 a8 = 0.0018T 2 + 1.9344T + 510.97 b8 b8 = 0.0008T 2 − 1.1069T + 389.09 c8 c8 =−0.00003T 2 + 0.0308T − 7.166

Mater. Express, Vol. 8, 2018 249 Materials Express Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy Lan et al.

(a)

(b)

IP: 192.168.39.210 On: Mon, 27 Sep 2021 07:01:00 Copyright: American Scientific Publishers Delivered by Ingenta Article

(c)

Fig. 6. (a) 723 K, (b) 823 K, (c) 923 K. Fitting and veriﬁcation of diffusion models at different heat treatment temperatures.

250 Mater. Express, Vol. 8, 2018 Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy Materials Express Lan et al.

Equation (6) actually determines the position of the coordi- Table IV. The electrochemical parameters-corrosion potential, corro- nate origin, its physical meaning is the concentration curve sion current density, anomalous slope, and cathode slope. C = C C = C on both sides and 1 and 2 two lines surrounded Heat treatment Corrosion Corrosion current by the same area, that is, temperature (K) potential (V) density (A/cm2babc

C C − m 2 293 −05391 1.3307 × 10 5 0.10273 −08391 xdC =− xdC (8) 723 −04623 2.417 × 10−6 0.12094 −036775 C C 1 m1 823 −04757 2.367 × 10−6 0.10123 −028151 − × −6 − The interface of the pattern satisfying the conditional 923 0 4379 2.145 10 0.12027 0 42239 formulas (7) and (8) is referred to the Matano plane. The concentration C in formula (6) can be obtained by (2) According to Eq. (8), we can find the Matano plane, substituting Cm and solve the area enclosed by the concentration distribution curve with C = C , C = C and x = 0 (Matano plane). Cm dC 1 xdC =− t D = tJ That is, the slope of the concentration distribution curve 2 2 C=Cm (9) C d C 1 Cm xdC C = C at the integral C and are solved. The result 1 The formula (9) shows that the integral area of the Matano obtained is brought into Eq. (10) to obtain the value of the plane is proportional to the component passes through the diffusion coefficient. This method of measuring the dif- diffuse flux of the Matano plane. Thus, the Matano plane fusion coefficient is usually called the Boltzmann-Matano can also be said to be a plane through which the diffu- method. The diffusion coefficient determined according to sion flux of the two components is equal. If the volume this method is the inter-diffusion coefficient. of the diffusion medium in the diffusion process is con- According to the Boltzmann-Matano method, we pro- stant, that is, the lattice constant does not change with the grammed Matlab and solved the inter-diffusion coeffi- concentration, and the vacancy maintains a concentration cients. The results are shown in Table II. equilibrium, then the Matano plane coincides with the ini- When the heat treatment temperature is 923 K, the dif- tial weld surface of the specimen. According to Eq. (6), the fusion coefficient is larger than the diffusion coefficient at Article diffusion coefficient at any concentration C is determined a temperature of 723 K, which is consistent with the diffu- experimentally: IP: 192.168.39.210 On: Mon,sion 27 Sep theory. 2021 This 07:01:00 trend conforms to those in the literature Copyright: American Scientificwith the Publishers values of the same order of magnitude (10−16. C xdC Delivered by Ingenta 1 C This phenomenon may be due to the presence of FeNi in D =− 1 (10) 2t dC/dC=C the mesophase, causing a certain degree of grain boundary diffusion. The steps for calculating the mutual diffusion coefficient At different temperatures, the relationship between the are: diffusion depth and the concentration is: (1) Using the boundary conditions of the diffusion in one- dimensional infinite medium and the required temperature, f = a1∗ exp−x−b1/c12+a2∗ exp−x−b2/c22 after the sample has been subjected to diffusion treatment +a3∗ exp−x−b3/c32+a4∗ exp−x−b4/c42 for a period of time, the concentrations of different posi- +a ∗ −x−b /c 2+a ∗ −x−b /c 2 tions are analyzed, and the concentration distribution curve 5 exp 5 5 6 exp 6 6 is determined. +a7∗ exp−x−b7/c72+a8∗ exp−x−b8/c82

–0.34 –0.1 –0.36 –0.2 –0.38 823K –0.3 –0.40 923K –0.42 –0.4 923 K 723 K –0.44 –0.5 823 K 723K –0.46 293 K –0.6 E vs Ag/AgCl/ V E vs Ag/AgCl/V –0.48 –0.7 –0.50 –0.8 –0.52 293K –0.54 –0.9 0 200 400 600 800 1000 1200 –8 –7 –6 –5 –4 –3 –2 Time/s i/A.cm–2

Fig. 7. Open circuit potential of samples at different temperatures. Fig. 8. Polarization curves of samples at different temperatures.

Mater. Express, Vol. 8, 2018 251 Materials Express Study on diffusion model and corrosion performance of nanocrystalline Fe–Ni alloy Lan et al.

Fig. 9. (a) 293 K, (b) 723 K, (c) 823 K, (d) 923 K. SEM images of nickel ﬁlms after 24 h in neutral salt spray test.

Temperature and the relationship between the various and −0.4757 V respectively. The heat treatment shows parameters are shown in TableIP: III. 192.168.39.210 On: Mon,that 27 Sep when 2021 the 07:01:00 temperature is 923 K, the corrosion ten- At the heat treatment temperaturesCopyright: of 723 K and American 823 K, Scientificdency is Publishers relatively small compared to the other two. The the Fe concentration distribution curve fitting wasDelivered selected, by Ingentaresults shown in Figure 8 and Table IV also indicate that and the diffusion model obtained, then the heat treatment the polarization curve moves to the left. The slope of the temperature of 923 K was chosen for the Fe concentra- anodic polarization curve is increased, as the thickness of Article tion distribution curve to verify this diffusion model. The the diffusion layer increases. The corrosion potential of the result is shown in Figure 6, the results show that the above nickel plating layer after heat treatment is higher than that diffusion model is correct. of the nickel plating layer without heat treatment, which improves the corrosion performance of the nickel plating 3.4. Electrochemical layer. By all measures, the 923 K corrosion current density − The evolution of OCP (Open Circuit Potential) over time is minimum (2.1452 × 10 6 A/cm2, so the stability of its for the samples of all four orientations, as indicated as alloying film is the best of the experimental materials. shown in Figure 7. The results do not indicate signifi- cant differences in behavior among the different heat treat- 3.5. Corroded Surface Morphology ments, and it can be seen that after heat treatment the other Figure 9 shows SEM images obtained after the Neutral samples exhibit a positive trend in OCP values. This indi- Salt Spray test. Samples with different heat treatment tem- cates that with increasing temperature, the diffusion layer peratures showed different corrosion morphology on the thickness of nano iron and nickel plating increases, and surface after 24 hours of experiments in the neutral salt the corrosion resistance of the sample increases. spray test. After the neutral salt spray test, when the sam- Tafel curve shows the polarization curves of different ple was not subjected to a heat treatment test, a lot of materials in the simulated solution. The corrosion poten- pitting occurred on the surface, as shown in Figure 9(a); tial and corrosion current density of different materials when the heat treatment temperature is 723 K, the number in the simulated solution are listed in Table IV. Gener- of pitting on the surface of the sample decreases, such as ally, the greater the positive corrosion potential, the better Figure 9(b); with the increase of the heat treatment tem- protection performance of the passive film. As the heat perature, the number of pitting corrosion on the surface of treatment temperature increases, the corrosion potential the specimen was reduced until no pitting occurred on the of the plating gradually increases. When the heat treat- specimen surface, as shown in Figures 9(c) and (d). There- ment temperature was 923 K, the plating had the high- fore, the results of this experiment show that as the heat est corrosion potential, and its value was −0.4379 V. The treatment temperature increases, the corrosion resistance other two kinds of corrosion potentials are −0.4623 V, of the plating is significantly improved.

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4. CONCLUSION 6. G. Liu, S. C. Wang, X. F. Lou, J. Lu, and K. Lu; Low carbon We have adopted shot peening technology on the surface steel with nanostructured surface layer induced by high-energy shot of low carbon steel, which can make its surface grain peening; Script. Mater. 44, 1791 (2001). 7. P. Wu and J. Y. Wang; Internal frictional elastic study on surface size reach the micro-nano level. As the shot peening time nanocrystallized 304 stainless steel induced by high-energy shot increases, the finer the surface grain becomes. When the peening; J. Mater. Sci. Tech. 18, 132 (2002). constant pressure was 0.3 MPa, the steel ball size was 8. Z. B. Wang, N. R. Tao, S. Li, W. Wang, G. Liu, J. Lu, and K. Lu; 0.3 mm, the shot peening time was 15 minutes, and the Effect of surface nanocrystallization on friction and wear properties average grain size of the sample surface was 256 nm. in low carbon steel; Materials Science and Engineering 352, 144 (2003). According to the error function, the diffusion model 9. Y. S. Zhang and Z. Han; Fretting wear behavior of nanocrystalline of the inter-diffusion layer by Matlab software pro- surface layer of copper under dry condition; Wear 265, 396 (2008). gramming was obtained. As the heat treatment temper- 10. M. Wen, G. Liu, J. F. Gu, W. M. Guan, and J. Lu; The tensile proper- ature increases, the diffusion layer thickness and the ties of titanium processed by surface mechanical attrition treatment; inter-diffusion coefficient increase. When the heat treat- Surf. Coat. Technol. 202, 4728 (2008). 11. F. A. Guo, Y. L. Ji, Y. N. Zhang, and N. Trannoy; Local ther- ment temperature is 923 K, the diffusion layer thickness mal property analysis by scanning thermal microscope of ultrafine- and inter-diffusion coefficient are 18.59 m and 9.36 × grained surface layer in copper and in titanium produced by surface 10−16 m2/s, respectively. mechanical attrition treatment; Mater. Charact. 58, 658 (2007). At different temperatures, the relationship between the 12. S. Zherebtsov, T. Naoe, M. Futakawa, and K. Maekawa; Erosion diffusion depth and the concentration is damage of laser alloyed stainless steel in mercury; Surf. Coat. Tech- nol. 201, 6035 (2007). f = a1∗ exp−x−b1/c12+a2∗ exp−x−b2/c22 13. V. P. Rotshtein, Y. F. Ivanov, A. B. Markov, D. I. Proskurovsky, and K. V. Karlik; Surface alloying of stainless steel 316 with copper +a3∗ exp−x−b3/c32+a4∗ exp−x−b4/c42 using pulsed electron-beam melting of film–substrate system; Surf. Coat. Technol. 200, 6378 (2008). ∗ 2 ∗ 2 +a5 exp−x−b5/c5 +a6 exp−x−b6/c6 14. C. Navas, R. Colaço, J. D. Damborenea, and R. Vilar, Abrasive wear ∗ ∗ behaviour of laser clad and flame sprayed-melted NiCrBSi coatings; +a7 exp−x−b7/c72+a8 exp−x−b8/c82

Surf. Coat. Technol. 200, 6854 (2006). Article 15. Q. Ming, L. C. Lim, and Z. D. Chen; Laser cladding of nickel-based The higher the heat treatment temperature, the better the hard facing alloys; Surf. Coat. Technol. 106, 174 (1998). corrosion resistance of the nanometerIP: 192.168.39.210 Fe–Ni plating layer.On: Mon,16. 27A. Sep Conde, 2021 F. Zubiri, 07:01:00 and Y. J. D. Damborenea; Cladding of Ni–Cr– When the heat treatment temperatureCopyright: is 923 K, American the cor- ScientificB–Si Publishers coatings with a high power diode laser; Mater. Sci. Eng., A Delivered by Ingenta rosion potential and the corrosion current density are 334, 233 (2002). −0.4379 V and 2.145 × 10−6 A/m2, respectively. 17. L. C. Lim, Q. Ming, and Z. D. Chen; Microstructures of laser- clad nickel-based hard facing alloys; Surf. Coat. Technol. 106, 183 (1998). Acknowledgments: The authors acknowledge the Sci- 18. S. Zherebtsov, T. Naoe, M. Futakawa, and K. Maekawa; Erosion entiﬁc Research Fund Project of Chongqing University damage of laser alloyed stainless steel in mercury; Surf. Coat. Tech- of Science and Technology (CK2015Z18) and the Suc- nol. 201, 6035 (2007). 19. C. Sudha, P. Shankar, R. V. S. Rao, R. Thirumurugesan, and cessful Transformation Project of Chongqing University M. Vijayalakshmi; Microchemical and microstructural studies in a (KJZH17136) for their ﬁnancial support. PTA weld overlay of NiCrSiB alloy on AISI 304L stainless; Surf. Coat. Technol. 202, 2103 (2008). 20. D. I. Pantelis, A. Griniari, and C. Sarafoglou; Surface alloying of References and Notes pre-deposited molybdenum-based powder on 304L stainless steel

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Received: 19 November 2017. Revised/Accepted: 5 May 2018.

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