Microstructure and high-temperature wear behaviour of Inconel 625 multi-layer cladding prepared on H13 mould steel by a hybrid additive manufacturing method

Prévia do material em texto

Journal of Materials Processing Tech. 291 (2021) 117036
Available online 30 December 2020
0924-0136/© 2020 Elsevier B.V. All rights reserved.
Microstructure and high-temperature wear behaviour of Inconel 625 
multi-layer cladding prepared on H13 mould steel by a hybrid additive 
manufacturing method 
Jingbin Hao a,b,*, Fangtao Hu a,*, Xiawei Le a, Hao Liu a, Haifeng Yang a, Jing Han a 
a School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, China 
b Jiangsu Engineering Technology Research Centre on Intelligent Equipment for Fully Mining and Excavating, China University of Mining and Technology, Xuzhou, China 
A R T I C L E I N F O 
Associate Editor: Jian Cao 
Keywords: 
Hybrid additive manufacturing 
Laser cladding 
Ultrasonic surface rolling 
Inconel 625 
H13 steel 
Microstructure 
High-temperature wear behaviour 
A B S T R A C T 
To improve the high-temperature performance of a hot-working mould, high-temperature wear-resistant multi- 
layer laser cladding was prepared on the forming surface of the mould by a hybrid additive manufacturing 
(HAM) method. First, an Inconel 625 multi-layer cladding was fabricated on the H13 mould steel by laser 
cladding. Then, the multi-layer laser cladding was milled by CNC. Finally, the milled multi-layer cladding was 
subjected to ultrasonic surface rolling (USR) treatment. The microstructure and high-temperature wear behav-
iour of the multi-layer cladding prepared by HAM were studied using SEM, EDS, and a high-temperature trib-
ometer. The results show that the multi-layer laser cladding after USR has a smooth nanolayer. The surface 
roughness is below 0.15 μm. The multi-layer cladding has better high temperature wear resistance than the 
substrate. The microstructure of the multi-layer cladding from the surface to the substrate is composed of coaxial, 
columnar, and dendritic grains. After USR treatment, the dendritic grains are grown in the processing direction 
and significantly refined. 
1. Introduction 
With the development of the moulding industry, the mould steel has 
been also developing rapidly. Due to the development of industrial 
production techniques and the continuous emergence of new materials, 
the working conditions of moulds are becoming more onerous, and new 
requirements are constantly being imposed on the performance, quality, 
and variety of mould steels. Higher-grade manufacturing tools are 
required to satisfy the continuous development of extreme 
manufacturing (Guo and Lu, 2019), at the same time, tool wear in the 
manufacturing has been becoming increasingly complicated (Jiang 
et al., 2020). H13 steel is the most widely applied and most represen-
tative type of hot-work die steel: it has the characteristics of high 
hardenability and high toughness; has excellent crack resistance, and 
could be water-cooled when used in-service; however, its 
high-temperature wear resistance is moderate. While re-heating to 
above 540 ℃, its hardness decreases rapidly. To improve the perfor-
mance of H13 steel to meet the production requirements, researchers 
have continued to study its properties and behaviour. The earliest 
methods used to improve its performance involved adding other metal 
elements to H13 (Yongliang, 1997); Gao et al. added rare earth to H13, 
and found that adding 0.015 wt.% of rare earth could improve the 
mechanical properties of H13 (Gao et al., 2015). Later, people modified 
the surface of H13 steel to improve its high-temperature wear resistance 
and corrosion resistance. Chang et al. conducted surface oxidation 
research on H13 steel and found that the oxide layer can enhance the 
polarisation resistance and quickly generate a passivation layer to 
improve the corrosion resistance (Chang et al., 2010). Liu et al. com-
bined shot-peening and nitriding to fabricate a composite nitriding layer 
on the surface of H13 steel, and studied its thermal fatigue cracking 
performance (Liu et al., 2019a). With the development of laser cladding 
technology, many scholars used laser prepared a cladding layer on the 
surface of H13 steel to improve the performance of H13 steel and meet 
the requirements of various working conditions. The cladding layer 
prepared by Tong et al. using a mixed powder of 75 % Cr and 25 % Ni on 
the surface of H13 had better anti-cracking, anti-oxidation, and corro-
sion properties (Tong et al., 2013). Others prepared a nanolayer on the 
surface of H13, and the wear resistance and corrosion resistance of this 
layer were significantly improved (Jiang and Molian, 2001). 
Ultrasonic surface rolling (USR) technology is a new type of 
* Corresponding author at: School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, China. 
E-mail address: fangtaohu@cumt.edu.cn (J. Hao). 
Contents lists available at ScienceDirect 
Journal of Materials Processing Tech. 
journal homepage: www.elsevier.com/locate/jmatprotec 
https://doi.org/10.1016/j.jmatprotec.2020.117036 
Received 2 August 2020; Received in revised form 17 December 2020; Accepted 23 December 2020 
Journal of Materials Processing Tech. 291 (2021) 117036
2
ultrasonic assisted surface modification method. This method could 
promote the nanocrystallisation of surface grains. Nanocrystalline ma-
terials exhibit unique properties superior to traditional coarse-grained 
materials because of their small grain size (usually less than 100 nm), 
high interface density, and large volume fraction (Lu and Lu, 2004). If a 
certain thickness and performance of nanostructured crystal layer can be 
prepared on the surface of the traditional coarse-grained material, then 
the overall performance of the material can be greatly improved through 
the optimisation of the surface texture performance: not only can 
traditional materials be better utilised, it also reduces production costs 
(Wang et al., 2019). The gradient nanostructure prepared by Wang et al. 
on the surface of IF steel by USR technique can suppress the generation 
of cracks under high load and has good wear resistance (Wang et al., 
2018). Cheng et al. found that the samples have the longest fatigue life 
by comparing the USR process with the traditional process (Cheng et al., 
2016). Huang et al. prepared nanolayers on the surface of 316 L steel by 
USR technology, and found that nanometric particles enhanced the fa-
tigue resistance by suppressing the generation of cracks and adapting to 
the amplitude of cyclic plastic strain (Huang et al., 2015). 
At present, laser cladding technology has been used to prepare high- 
quality multi-layer cladding (Heigel et al., 2016); Liu had conducted 
laser cladding of cast iron to build a well bonded NiCoCr alloy coating 
using a multi-layer cladding deposition approach instead of preheating 
(Liu et al., 2016), therefore, in the present research, a hybrid additive 
manufacturing (HAM) method that integrates multi-laser cladding and 
USR technology was used to prepare a high-temperature alloy cladding 
layer with a nanolayer on the surface of H13 steel to enhance the 
high-temperature wear resistance of H13 steel. 
2. Experimental work and material characterisation 
2.1. Materials and experimental design 
The HWL-RW1500 system was used to prepare the cladding layer. 
The system is mainly composed of a semiconductor laser as a fibre- 
coupled continuous output laser with a coaxial powder feeding device, 
the powder feeder model is an HW-02SF device. High-purity Inconel 625 
spherical alloy powder was selected as the original powder, its particle 
size is 45− 105 μm, and its chemical composition is summarised in 
Table 1. 
Argon was used as the protective gas, one, three and six layers of 
multi-layer and multi-pass cladding were prepared on the surface of H13 
steel by coaxial powder feeding. The optimised laser parameters were as 
follows: a laser power of 1400 W, a scanning speed of 3.33 mm/s, a 
powder-feeding rate of 3.8 g/min, a spot diameter of 2 mm, a carrier gas 
flowrate of 4 L/min, and an overlap rate of 42 %. After comparing and 
studying the chessboard scanning strategy, the zig-zag scanning strategy 
and the re-melting scanning strategy(Gu et al., 2020), a more suitable 
method was developed to obtain high-quality cladding layer and the 
scanning path is shown in Fig. 1: each layer used two scanning directions 
and the scanning directions of two adjacent layers differ. 
2.2. USR process 
After cladding, the cladding layer was milled, and then USR was 
performed at room temperature (this USR procedure was repeated four 
times. The following parameters were used: a rolling ball diameter of 
14 mm, an ultrasonic vibration frequency of 28 kHz, a vibration 
amplitude of 5 μm, and an applied static force of 300 N. The processes of 
SLC and USR are shown in Fig. 2, and the result of HAM is illustrated in 
Fig. 3. 
2.3. High-temperature friction and wear test 
The HT-1000 high-temperature friction and wear tester was used to 
compare the friction and wear experiments of the samples before and 
after rolling at a temperature of 600 ℃. Before the experiment, we 
removed surface defects from the abrasion samples with sandpaper, then 
cleaned them with alcohol. The experimental parameters were: grinding 
ball with a rotation radius of 2.5 mm, loading 5 N, friction applied at 
600 rpm, wearing time of 20 min, and 6-mm diameter grinding balls 
made of Si3N4. 
2.4. Microstructural analysis 
The sample was cut into pieces measuring 5 mm × 5 mm × 3 mm, 
polished, and etched with aqua regia. The microstructure and composi-
tion distribution of the cladding layer were ascertained by a scanning 
electron microscope (SEM) with an energy dispersive spectrometer 
(EDS). 
2.5. Micro-hardness test 
The MTHV-1MMDTe type hardness tester was used to measure the 
microhardness of the cladding layer, the applied load was 500 gf, and 
Table 1 
Main chemical composition of Inconel 625. 
Main chemical composition (wt%) 
Cr C Si Al Co Mo Nb Ti Mn Fe Ni 
20− 30 ≤0.1 ≤0.5 ≤0.4 ≤1 ≤8− 10 3.15− 4.15 0.65− 1.15 0.5 ≤5 Bal. 
Fig. 1. The scanning strategy. 
Fig. 2. Schematic of laser cladding (a) and ultrasonic rolling (b). 
J. Hao et al. 
Journal of Materials Processing Tech. 291 (2021) 117036
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the pressure holding time was 10 s. The hardness at a given position was 
measured three times and the mean average taken. 
3. Results and discussion 
3.1. Multi-layer cladding process and cladding layer height 
When repairing hot-working moulds, it is necessary to form multiple 
layers and multiple layers of cladding. The overlapping rate and the Z- 
axis lift are important factors that affect the quality of the multilayer lap 
cladding. Setting the overlapping rate as a variable, 30 %, 40 %, and 50 
% overlapping rates were set to conduct the cladding experiment on the 
substrate: it was found that a 40 % overlapping rate provided a better 
surface quality. We continued to search around 40 %, finding that a 42 % 
overlapping rate has the best cladding quality while other process 
parameters remain unchanged. 
When performing multi-layer cladding, the lifting amount ΔZ on the 
Z-axis needs to be controlled. ΔZ should be consistent with the thickness 
of the single-pass cladding layer to ensure the same cladding process 
conditions for each layer; however, in actual multi-layer cladding, 
thermal deformation of parts and other factors will cause a certain de-
viation between ΔZ and the thickness of a single cladding layer. As a 
result of the cumulative effect, the accuracy of the multi-layer cladding 
is decreased; therefore, it is necessary to ensure the accuracy and 
reasonableness of lifting amount ΔZ. 
According to the cladding strategy in this article, the value of ΔZ is 
determined according to the calculation model of multi-layer cladding 
over a single track, as shown in Fig. 4, and then adjusted accordingly 
according to specific experiments. This model makes the following as-
sumptions: (1) The cross-section of each cladding layer is a circular arc, 
and the cross-sectional area is equal; (2) The curvature of the track re-
mains unchanged after cladding (Zhu et al., 2010). 
In theory, it is necessary to ensure that after cladding a layer, it re-
mains flat relative to the previous layer, so 
SABH = SBCD + SGHF 3a) 
SCDFG = SOAFD − SOFD (3b) 
FD = W,AE = h,CD = ΔZ (3c) 
ΔZ =
(
4h2+w2
8h
)2
arcsin
(
4Wh
4h2+w2
)
−
W(W2 − 4h2)
16h
W
(3d) 
where r is the radius of the arc, h represents the height of a single 
cladding, and W is the width of a single track. 
It can be seen from the above formula that ΔZ is a function of the 
width W and the height h of the single track. In practice, the width and 
height of the single reverse cladding layer should be determined 
Fig. 3. The sample of hybrid additive manufacturing; a represents the sample after laser cladding, b is the sample after milling, c is the sample after USR. 
Fig. 4. The Z-axis cladding lift calculation model. 
Fig. 5. The section of samples after HAM; a is the section through one-layer cladding, b is the section through three-layer cladding, c is the section through six- 
layer cladding. 
J. Hao et al. 
Journal of Materials Processing Tech. 291 (2021) 117036
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according to the results of the cladding process experiment, and then ΔZ 
is derived through the above formulation. 
Fig. 5 shows the sections of samples after HAM, the average height 
increased significantly as the number of layers increasing; the average 
height of a single cladding layer is 2.2 mm, the average height of the 
three layers is 5.2 mm, and the average height of the six layers is 
9.6 mm. 
3.2. Microstructure and EDS analysis of multi-layer cladding 
It can be seen from Fig. 6 that the first cladding layer forms metal-
lurgical bond with the substrate, in result of the maximum temperature 
gradient and slow growth rate, planar crystals appear at the junction 
(Zhang et al., 2015). Planar crystals are also found between the substrate 
and the first layer and between the first layer and the second layer, 
which appear as white and bright colour bands between the two regions 
(Figs. 6a and 6b). 
Fig. 7 illustrates the microstructure diagram of the middle part in the 
multi-layer laser cladding both before USR and after USR. It could be 
seen in Figs. 6 and 7 that both samples show the same composition, the 
cladding layers were composed of planar crystals, cellular crystals, 
equiaxed crystals, and dendritic crystals from bottom to top. This phe-
nomenon was related to the temperature gradient G and the solidifica-
tion rate R during the solidification of the cladding layer. 
As shown in Fig. 8, the value of G/R may cause a change in the so-
lidification method, the value of product GR determines the size of the 
solidification structure (Liu et al., 2019b); at the bottom near the sub-
strate, faster heat dissipation leads to a larger temperature gradient 
during solidification and a faster solidification rate, so planar crystals 
are formed here. The first layer dissipates heat faster, so when the sec-
ond layer is cladding, the value of G/R is still large enough to form 
planar crystals, thus a white and bright colour band can still be observed 
at the junction between the two layers. The temperature continues to 
increase with the increase in the number of cladding layers, so the value 
of G/R from the third layer is not large enough to form planar crystals, 
Fig. 6. a is the first layer after USR, b is the first layer before USR. 
Fig. 7. a is themicrostructure diagram of the middle part of the multi-layer laser cladding sample after USR; b is the microstructure diagram of the middle part of the 
multi-layer laser cladding sample after USR. 
Fig. 8. The effects of G and R on the morphology and scale of the solidified 
microstructure; G/R determines morphology of solidified structure, GR de-
termines the size of the solidified structure. 
J. Hao et al. 
Journal of Materials Processing Tech. 291 (2021) 117036
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and more equiaxed dendrites appear. As the top layer is in contact with 
the air and the movement of the laser, the direction of G is changed, so 
dendrites which are growing along the direction of laser scanning 
appear on the top of the top layer (Luo et al., 2019). 
The USR processing head can apply a certain amplitude of ultrasonic 
mechanical vibration along the normal direction of the workpiece sur-
face. Under a certain feed condition, the working head transmits the 
static pressure and ultrasonic shock vibration to the surface of the 
rotating mechanical parts, resulting in a crushing effect, thus, the metal 
undergoes substantial elasto-plastic deformation. After USR, the surface 
of the workpiece shows a certain degree of elastic recovery, and the 
generated plastic flow fills the valleys on the surface of the workpiece 
with peaks, thereby greatly reducing the surface roughness Ra to the 
nanometric level and improving the comprehensive performance in-
dicators of the surface (Yang et al., 2017). Meanwhile, under the com-
bined action of ultrasonic impact and static pressure rolling, the violent 
and uniform plastic deformation on the surface of the metal workpiece 
will inevitably cause the original crystal grains on the surface of the 
workpiece to be broken and refined. Reciprocating processing can make 
the surface of the part evenly stressed, while increase the amount and 
depth of deformation, to achieve crystal grains with further refinement 
and homogenisation, thereby obtaining a nanostructured layer (Sun 
et al., 2017). 
Fig. 9 illustrates the surface profile before and after USR; after USR 
the surface roughness decreased from 0.355 μm to 0.120 μm. After USR, 
severe plastic deformation had occurred; it is well known that severe 
plastic deformations are beneficial in obtaining ultrafine-grained 
metallic materials accompanied by the improvements of mechanical 
properties such as microhardness and strength. The plastic deformation 
can refine grains and increase dislocation density. The dislocation slip-
ping, accumulation, and rearrangement can lead to formation of small- 
angle grain boundaries and substructures, which can improve its me-
chanical properties (Wenbo et al., 2019). As shown in Fig. 10, under the 
dual action of static pressure and ultrasonic vibration, the surface of the 
sample processed by USR, and the crystal grains are squeezed and 
elongated. As illustrated in Fig. 10a, the top of the surface is a severely 
deformed region that is plastically deformed, the particles are extruded, 
elongated, and the growth direction is parallel to the machined surface. 
In the middle of the surface slight plastic deformation occurs, the growth 
of the dendrites is oriented towards the processing direction, and the 
dendrites are remarkably refined. Fig. 10a demonstrates the surface 
after USR which is a nanolayer with a thickness of about 20 μm formed 
parallel to the processing direction. 
X-ray energy spectrum (EDS), is used to analyse the types and con-
tents of elements in the micro-region of the material by using SEM and 
transmission electron microscope (TEM): using the characteristic X-rays 
generated when electron beams interact with substances. EDS provides 
information on the chemical composition of the sample, qualitatively 
and semi-quantitatively detecting most elements. A three-layer cladding 
layer is selected as the research object to study the changes in element 
content in the cladding layers with depth after multilayer laser cladding. 
Fig. 11 shows the EDS line scan analysis result of the Ni, Fe, Cr, and 
Mo contents of three-layer laser cladding from top to bottom. In the 
multi-layer cladding, the contents Ni, Fe, Cr, and Mo are uniformly 
Fig. 9. The surface roughness before USR(a) and after USR(b). 
Fig. 10. a is the surface of multi-layer cladding after USR, b is the surface of multi-layer cladding before USR. 
Fig. 11. Line scanning analysis of the three-layer cladding layer. 
J. Hao et al. 
Journal of Materials Processing Tech. 291 (2021) 117036
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distributed along the depth direction. This uniform element distribution 
is attributed to the re-melting of the pre-cladding layer, indicating that 
the previous layer must undergo solidification and re-melting can 
strengthen the interlayer bonding strength of multi-layer cladding, 
enhance the quality of multi-layer cladding, and improve the moulding 
quality and service life of remanufactured parts. 
The EDS results in Fig. 11 also demonstrate that the upper and lower 
composition in the bonding zone between the substrate and the bottom 
layer shows a significant change, but the composition in the bonding 
zone is relatively stable, possibly because, during laser cladding the el-
ements in the cladding layer and the substrate penetrate each other to 
form a bonding zone with uniform composition and a certain thickness. 
The bonding zone with a certain thickness indicates that the great 
dilution of multi-layer cladding, the bonding strength between the 
cladding layer and the substrate will be enhanced with the increasing of 
the dilution, which implies that the two parts are well bonded. 
3.3. High-temperature friction and wear behaviour 
As shown in Figs. 12(b, d, and f), there are scratches along the sliding 
direction on the wear surface of the sample before USR, showing a 
furrow-like morphology, which indicates that abrasive wear occurs on 
the surface; for the sample examined before USR, the surface roughness 
is larger, and the rough peak is sharper, therefore the furrow is more 
easily formed, and the abrasive wear is more severe; the wear surface of 
the sample before USR is oxidised, because the load applied by the 
grinding ball to the sample causes local adhesion of the contact surface, 
and then during the relative sliding process, the adhered part is sheared 
Fig. 12. a, c, and e are the sample after USR; b, d, and f are the sample before USR; c and d are grooves. 
J. Hao et al. 
Journal of Materials Processing Tech. 291 (2021) 117036
7
to form blocky peeling features, and some of the oxide thus removed is 
compacted by the grinding ball to form a bulging massive oxide layer, 
this is a typical feature of adhesive wear, at the same time, plastic 
deformation and tear-like fractures caused by adhesive wear are 
observed. When the friction pair components move relative to each 
other, the plastic deformation of the surface accelerates the diffusion of 
oxygen into the metal, forming an oxide layer, due to the low strength of 
the resulting oxide film, it is peeled off by the grinding ball and caused 
oxidative wear. 
Compared with the sample after USR, as shown in Figs. 12 (a, c, and 
e), the area and depth of oxide exfoliation of the sample before USR are 
significantly increased; abrasive wear causes more groovesand their 
width and depth are significantly increased. The grooves on the samples 
before USR always connect with the regions of exfoliation, however, the 
grooves in the samples after USR are slender and mutually independent. 
Differing from the continuous large area peeling off, the peeling-off re-
gions of the samples after USR are more widely scattered. In the samples 
examined after USR, there is little debris adherent to the regions of 
exfoliation, but in the samples inspected before USR the regions of 
exfoliation are covered in such debris: the debris will further aggravate 
the abrasive wear. Figs. 12 (e and f) show the adherent regions on the 
surface of the samples after USR as larger than those seen beforehand; 
these adherent regions consist of a broken oxide film, the increase in the 
area of the adherent regions can play a better protective role and relieve 
the wear and peel of the soft continuous substrate on the coating surface. 
These show that the sample (after USR) has a better high-temperature 
wear performance. 
Comparing the friction coefficient before and after rolling, as shown 
in Fig. 13, the friction coefficient after rolling is always lower; in the first 
five minutes, the large friction coefficient is due to the large number of 
fine particles attached to the wear surface, which results in a large 
contact stress during the grinding process. The friction coefficient de-
creases and remains stable at 0.42 after five minutes of the high- 
temperature friction and wear experiment (possibly because the fric-
tion oxide blocks hinder the direct contact between the sample and the 
counter-rotating balls, thus contributing to the reduction in the coeffi-
cient of friction and the wear and tear). 
3.4. Micro-hardness 
Microscopic hardness is an important feature used to measure the 
mechanical properties of the cladding layer. Fig. 14 illustrates the dis-
tribution of the microhardness along the depth of the cross-section of 
single-layer, three-layer and six-layer laser cladding. It can be seen that 
the average hardness of the cladding layer is 277.4 HV, which is 
significantly higher than the average hardness of the substrate 
(248.7 HV): the average surface hardness of the parts after HAM is 
547.5 HV, which is significantly higher than that of the substrate. This is 
mainly because, in the HAM process, it is equivalent to work-hardening 
of the surface of the cladding layer, and USR breaks the grains on the 
surface of the parts, the grain size is refined, the interface increases, and 
dislocations are hindered, thus further improving the surface hardness of 
the parts. 
USR subjects the surface of the cladding layer to a certain depth of 
plastic deformation, so that the original crystal grains are broken and 
refined. The reciprocating processing generates a uniform stress on the 
surface of the cladding layer, also it increases the amount and depth of 
deformation to refine the crystal grains, thus, a certain depth of nano-
layer is obtained. The increase in surface hardness of the cladding layer 
is attributed to the combined effect of grain refinement and work 
hardening, therefore, the nanostructure of the metal surface is 
confirmed to increase the surface hardness after multilayer laser clad-
ding, and then improve its fatigue resistance and abrasion resistance. 
4. Conclusions 
(1) We successfully prepared high-quality one-layer, three-layer, and 
six-layer cladding layers on the surface of H13 die steel through a hybrid 
additive manufacturing (HAM) method. The bonding between the 
layers, the cladding layer and the substrate is satisfactory. The entire 
cladding layer is composed of planar crystals, cellular crystals, equiaxed 
dendrites, and dendrites from bottom to top. 
(2) After USR, the surface roughness is reduced from 0.355 μm to 
0.120 μm. The surface of the cladding layer (after USR) forms a nano-
layer with a depth of about 20 μm. This is the zone of plastic deforma-
tion after USR: the dendritic grains therein are squeezed, elongated, and 
thus refined. 
(3) Through HAM, the surface hardness of a hot-working mould is 
significantly improved: this plays an important role in improving its 
fatigue resistance and wear resistance. 
(4) The high-temperature friction and wear experiment results show 
that the wear mechanisms of the cladding layer before and after USR are 
similar; compared with the sample before USR, the cladding layer after 
USR has a smaller coefficient of friction, and suffers less wear. 
CRediT authorship contribution statement 
Jingbin Hao: Conceptualization, Funding acquisition, Supervision, 
Validation, Writing - review & editing. Fangtao Hu: Formal analysis, 
Investigation, Methodology, Writing - original draft. Xiawei Le: 
Fig. 13. Friction coefficient of the sample before USR (A) and the sample after 
USR (B). 
Fig. 14. The distribution of the microhardness along the depth of the cross- 
section of single-layer, three-layer, and six-layer laser cladding. 
J. Hao et al. 
Journal of Materials Processing Tech. 291 (2021) 117036
8
Investigation. Hao Liu: Resources. Haifeng Yang: Resources. Jing Han: 
Resources. 
Declaration of Competing Interest 
The authors declare that they have no known competing financial 
interests or personal relationships that could have appeared to influence 
the work reported in this paper. 
Acknowledgements 
This work was supported by the Fundamental Research Funds for the 
Central Universities (2020ZDPYMS22), and the Priority Academic Pro-
gram Development of Jiangsu Higher Education Institutions (PAPD). 
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