Ebook: Advances in Machinery, Materials Science and Engineering Application IX
New engineering materials, techniques and applications are constantly being researched and developed, and keeping up to speed with the latest advances is crucial for engineers if they are to successfully address the challenges they face in their work.
This book presents the selected proceedings of MMSE2023, the 9th International Conference on Advances in Machinery, Materials Science and Engineering Applications, jointly organized by the SAE-Supmeca, France and China University of Geosciences (Wuhan) and held on 22 and 23 July 2023 in Wuhan, China. For the past 12 years, this annual conference has collated recent advances and experiences, identified emerging trends and provided a platform for participants from academia and industry to exchange information and views, helping to address the world’s machinery and engineering challenges. The book contains 4 sections: mechanical engineering, material science and manufacturing technology; electrical engineering, automation and control; modeling, simulation and optimization techniques in engineering; and advanced engineering technologies and applications. A total of 241 submissions were received for MMSE2023, of which 151 papers were selected for the conference and for publication by means of a rigorous international peer-review process. These papers present exciting ideas and methods that will open novel research directions for different communities.
Offering a current overview of the latest research and applications in machinery and materials-science engineering, the book will be of interest to all those working in the field.
The 9th International Conference on Advances in Machinery, Materials Science and Engineering Applications (MMSE2023) was held in Paris, France and Wuhan, China on 22–23 July 2023. The conference was organized by the SAE-SUPMECA, France and China University of Geosciences (Wuhan) and co-sponsored by Laboratoire Quartz, France, the Institute of Materials, Minerals and Mining (IOM3) UK, National University of Singapore, University of Huddersfield, UK, Jiangnan University and Wuhan University of Sciences and Technology, China, University of Electronic Science and Technology of China, and Rongzhi Academic Center, China, among others.
There are 4 sections in this volume: Mechanical Engineering, Material Science and Manufacturing Technology; Electrical Engineering, Automation and Control; Modelling, Simulation and Optimization Techniques in Engineering; Advanced Engineering Technology and Application. This volume comprises the 151 papers selected from 241 submissions by means of a rigorous international peer-review process. These papers present exciting ideas and methods that will open novel research directions among different communities.
We sincerely appreciate the efforts of all the participants who contributed their latest research to this volume and thank our keynote speakers: Prof. David BASSIR, Université Technologique de Belfort-Montbéliard, France; Prof. Xuejun (James) Ren, Liverpool John Moores University, UK; Dr. Qiang Xu, University of Huddersfield, UK; Prof. Michael Todinov, Oxford Brookes University, UK; Prof. Raul Duarte Salgueiral Gomes Campilho, ISEP – School of Engineering, Porto, Portugal; and Dr. Li Wang, Queen Mary University of London, UK, for their excellent speeches. Thanks also to Prof. Seeram Ramakrishna, National University of Singapore, Singapore; Dr. Josh Sheng and all the reviewers involved for their kind support and work on this 9th edition of the MMSE proceedings. We would also like to express our sincere thanks to the publisher, IOS Press, for preparing this volume for publication.
We hope to see you again next year in Paris!
Professor Emin Bayraktar
22 July 2023
This paper highlights the advantages of using the cavitated volume fraction (fv) as a superior creep damage indicator compared to traditional two dimensional (2D) based parameters. With the emergence of three dimensional (3D) experimental techniques like X-ray tomography, in-situ volumetric observations have become feasible, enabling a more accurate assessment of creep damage. The cavitated volume fraction offers a comprehensive evaluation of cavity distribution, overcoming the limitations of missing information and the impact of cavity coalescence on 2D-based assessments. We present the procedure for deriving the cavitated volume fraction using the cavity size distribution function and the cavity growth pattern equation. Additionally, we discuss the potential application of the cavitated volume fraction for rupture time prediction using early-stage creep data. Overall, this paper emphasizes the importance of adopting 3D-based parameters, specifically the cavitated volume fraction, for improved creep damage assessment and lifetime prediction.
The paper investigates the possibility of delamination near the free edges of composites is investigated by the example of a two-dimensional formulation of the Pipes-Pagano problem. A bilinear material damage law based on the cohesive zone model (CZM) is considered. An example of selecting the stiffness of a cohesive layer is given, and a calculation of a laminated composite by the finite element method in the ANSYS program is performed. The method used makes it possible to determine the concentration of interlaminar stresses due to the edge effect, and, using a special set of interface elements simulating mating surfaces and following process of delaminaton, to investigate the composite delamination. When interface elements are added, the problem becomes non-linear and the solution in a two-dimensional formulation significantly reduces labor intensity and simplifies modeling, and also allows you to specify a large number of elements over the thickness of each layer. The problems with the convergence of the solution that have arisen can be eliminated with the help of special numerical modeling techniques and by varying the parameters embedded in the program. The revealed damage to the cohesive layer due to the edge effect can lead to delamination and premature failure of composites. The presented results can be used in the design of products from composite materials in rocket and space technology.
Traditional materials have certain restrictions in an industrial application today inhibiting them from the attainment of the best blend of toughness, density and strength. The paradigm shift in the use of agro-waste products as particulate reinforcement is an excellent choice owing to the inexpensive and availability of the desired agro-waste product. This research focuses on the development of AA6061 aluminium alloy through stir casting method using kaolinite clay as the reinforcement agent in increasing weight percentages of 2.5wt %, 5wt %, 7.5wt % and 10wt %.. The use of agro-waste as reinforcements is possible as the clay kaolinite was effectively infused into the pure matrix for composites to be constructed. The tensile strength was highest at the addition of 10 wt % of clay kaolinite. Brinell’s hardness test showed an increase in value with an increase in the mass fraction of clay. It was observed from the results of the tests carried out that the reinforced specimens exhibited improved hardness when analyzed using Brinell’s hardness machine. Some of these properties improved with the increase in weight percentage of reinforcement particles. This research has shown the importance of agricultural waste to material engineers, material handlers and metallurgists in our society and that it is the right way to go.
This paper studies and evaluates the mechanical properties of a blend of Polyethylene terephthalate (PET) and high-density polyethylene (HDPE). The HDPE/PET blends are prepared by injection molding PET into HDPE with a ratio of 0%, 10%, 20%, and 30%, respectively. After the injection molding, the samples are measured for tensile strength according to standard D638. As a result, the tensile values of HDPE/PET gradually decreased with the ratio of 0%, 10%, 20%, and 30% (PET) and 18.45, 17.31, 15.45, and 14.43 MPa, respectively. It was shown that the tensile strength of the HDPE/PET composite decreased gradually as the PET percentage increased because the penetration of PET in the HDPE structure increased the elastic modulus of the PET ratio, leading to a decrease in tensile strength. The packaging is known to be mostly blown from HDPE, which has many outstanding features. However, some disadvantages exist, such as low bending strength, low heat distortion temperature, low transparency, and, most importantly, packaging. The packaging blown from HDPE is unstable. This problem is a limited application of HDPE in the packaging industry. To improve the recycling of plastic packaging from HDPE, adding PET is the most effective way. PET plastic packaging is transparent, flexible, toxic, and difficult to recycle, so it can only be used once. Incorporating PET into HDPE will improve the transparency and mechanical properties of HDPE and reduce the cost of PET plastic, and reduce environmental pollution.
V1-xCrxN films were deposited via conventional magnetron sputtering (CMS) and plasma enhanced magnetron sputtering (PEMS) by controlling the power of Cr target and V target. The microstructure of films was characterized using scanning electron microscope, meanwhile, the thickness was measured. The chemical composition was analyzed by an energy dispersive spectrometer, and phase structure was analyzed by X-ray diffractometer. The hardness and Young’s modulus of films were evaluated using nano-indenter. With an increase in Cr content, the deposition rate increased gradually and then reduced in both V1-xCrxN films. As Cr content increased, CMS-V1-xCrxN films transformed from a mixture of FCC-V(Cr)N and FCC-VN with non-stoichiometric ratio to a mixture of FCC-V(Cr)N and BCC-Cr, and Cr content had no effect on the phase structure of PEMS-V1-xCrxN films, all of them shown FCC-V(Cr)N. In addition, the dominant texture in V1-xCrxN films deposited by CMS and PEMS were (111) and (200). As increasing Cr content, the density of the CMS-V1-xCrxN films increased gradually, moreover, all films were loose and porous. However, the Cr content had little effect on microstructure of PEMS-V1-xCrxN films, all of which shown dense columnar structure. With the increase of Cr content, the hardness and Young’s modulus of CMS-V1-xCrxN films increased gradually and then decreased, while which in PEMS-V1-xCrxN films were rise. The doping of Cr significantly improves the structure and mechanical properties of CMS-V1-xCrxN films. Furthermore, the structure of PEMS-V1-xCrxN films is much denser, and the mechanical properties of PEMS-V1-xCrxN films are significantly better than CMS-V1-xCrxN films.
When the high-pressure turbine of an aero-engine comes into contact with friction, the friction-heat effect that results raises the temperature at the site of contact quickly. In extreme circumstances, it will harm the blades and casing and impair the engine’s ability to function properly. A vane-casing thermo-solid coupling model was developed using the finite element method to study the impact of the frictional heat effect on local details at the contact point. The distribution rules of blade temperature and stress were examined when the rotational speed changed and whether the coating was applied to the casing inner surface. The findings indicate that there is a temperature asymmetry between the blade and casing and that the rubbing friction heat effect is primarily distributed on the contact surface between the blade and casing. The influence area is also small and will rise to a high temperature in a very short period. Temperature and stress are impacted by variations in rotational speed and the use of coatings. The temperature and stress peaks at blade contact can be greatly decreased by coating the inside surface of the casing. The frictional heat effect created by rubbing should be taken into account in real-world engineering issues.
The alloys with Sc content of 0 and 4 wt.% were prepared by vacuum hot press sintering using elemental Sc powder and Fe-21Cr-4Al pre-alloy powder as raw materials. The element Sc changed the XRD phases of Fe-21Cr-4Al alloy. In addition to the original matrix α-Fe phase, three Sc-rich phases are formed, namely, ScAlO3, Sc2O3 and Sc elemental. Meanwhile, Sc addition resulted in the formation of a protective corrosion product film on the corrosion face of alloy, which limited corrosion ion diffusion, thus reducing the corrosion rate of the alloy and enhancing its corrosion resistance. However, due to the lack of protective corrosion product film on the surface of alloys without Sc, large corrosion pits appear on the corrosion surface, and these pits continue to expand under the continuous erosion of corrosion ions. The corrosion speed of the alloy with Sc added was 4.302 mm/y, which was about 48.34% lower than that of the alloy without Sc.
Creep deformation is of vital importance on the thin-walled tube structure under external loadings, such as in-service cladding tubes. To improve the efficiency and accuracy of the creep deformation computation of the cladding tube, a novel continuum-based degenerated 5 degree of freedom (DOF) shell element is developed based on the continuum mechanics and finite element method. The degenerated shell element is implanted in the self-developed software BINE 2.0. The results of BINE 2.0 showed well agreement with commercial finite element software ABAQUS and analytical results. The ovality of the cladding middle section increases slowly at the beginning of the life and increases fast at the end of life until collapse due to the thermal and irradiation creep effect. The continuum-based shell element can be applied to the creep analysis of the cladding tubes of the nuclear reactor.
The mechanical properties of 20CrNiMo steel and the effects of notch with different fillet radii on tensile properties and tensile fracture morphology were studied by tensile tests on smooth specimens and notch specimens with different fillet radii. The results show that the 20CrNiMo steel has high strength, high toughness and high plasticity. The stress concentration and strain concentration at notch root can improve the yield strength and tensile strength of the material, but reduce its plasticity. The material has a good resistance to notch embrittlement. The notch sensitivity coefficient is greater than 1, and it is not sensitive to notch. The macro fracture of smooth specimens is cup-cone shape, and fiber region, radiation region, shear lip can be seen. The micro fracture morphology is dimple shape, showing good plasticity. The cracking of notched samples originated from a certain distance from the bottom of the notched samples, and the periphery expanded in a “radial” pattern. The micro-section morphology showed dimple and quasi-cleavage composite fracture, and the notched samples suffered from brittle transgranular fracture under tensile stress.
UiO-66 in Zr-MOFs materials stands out in the research of supercapacitors due to its large specific surface, high stability and high heat resistance. In this paper, pure UiO-66 was successfully prepared using solvothermal method, and three PDA/UiO-66 composites with addition mass ratio of UiO-66 and dopamine of 2:1, 3:1 and 4:1 were prepared by autopolymerizing dopamine hydrochloride to form polydopamine at room temperature. The materials’ morphology and structure were examined using SEM, TEM and XRD, and the capacitive performances were analyzed by CV and GCD. The results indicated that the capacitor properties of UiO-66 could be improved to a certain extent with the appropriate amount of polydopamine coating. The PDA/UiO-66 composite with a mass ratio of 2:1 displayed a high specific capacitance of 822.04 F/g at 1 A/g, and maintained good capacity retention even after 4000 charge/discharge cycles in a three-electrode system. These results suggested that the PDA/UiO-66 composite had great potential as a supercapacitor electrode material.
The thermal deformation behavior of 2219 alloy is studied by using the Gleeble-1500 thermal simulation testing machine under different deformation conditions, the deformation temperature is 350°C∼500°C and the strain rate is 0.01∼1s-1. The results show that when the strain rate increases, the flow stress also increases. However, when the deformation temperature increases, the flow stress decreases. Analyzing the deformed and solution treatment microstructure evolution of 2219 alloy though the electron back-scattering diffraction (EBSD). There are mainly deformed grains and only a few recrystallization grains of 2219 alloy after thermal deformed. When the deformation temperature is high and the strain rate is low, it is easy to occur dynamic recrystallization. After solution treatment, the microstructure of 2219 alloy occurs static recrystallization, which is advantageous at 350°C and 0.1s-1. When the deformation temperature is low and the strain rate is large, it is easy to occur static recrystallization after solution treatment. When 2219 alloy deforms at higher temperatures, using a higher strain rate can effectively suppress recrystallization.
Isothermal constant strain rate compression of Ti2AlNb-based alloys was carried out using a Gleeble-3500 thermal simulation tester with deformation temperatures of 650-850°C, strain rate interval of 0.001–1s-1, on the basis of which a modified Zerilli-Armstrong model and an optimised Zerilli-Armstrong model were developed to describe the thermal deformation behaviour of Ti2AlNb-based alloys. The results show that the error between the predicted and experimental values of the modified Zerilli-Armstrong model is larger, with correlation coefficients R and EAR of 0.935 and 12.4% respectively, while the optimised Zerilli-Armstrong model can predict the flow stress better, with correlation coefficients R and EAR of 0.964 and 10.5% respectively. The optimised Zerilli-Armstrong model had high prediction accuracy and wider applicability, making it more suitable as a constitutive model for predicting the thermal deformation behaviour of Ti2AlNb-based alloys.
Stainless steel pipe is widely used in machinery manufacturing industry, mainly used as steam, liquefied natural gas, natural gas, various petroleum products transmission pipeline. China is the largest consumer of stainless steel tube in the world, and in recent years the total consumption of stainless steel accounted for more than 20% of the total consumption in the world. Stainless steel pipe has good mechanical properties and good corrosion resistance, so it is widely used in the ocean engineering and shipbuilding industry, which is widely used in offshore oil and gas fields, deep water pumps, offshore drilling platforms, seabed mining devices, warships and other aspects. In this paper, the leakage of stainless steel seamless steel pipe used by a company is studied to discuss the failure behavior of stainless steel seamless steel pipe. The microstructure analysis shows that the fracture surface has the characteristics of stress corrosion crack. Chemical composition analysis, chemical composition of the sample GB/T 13296-2013 “Seamless Stainless Steel Tubes for Boilers and Heat exchangers” requirements for S31708 stainless steel; SEM and EDS detection: the corrosion products of seamless steel pipe fracture and the scale composition in the tube were detected. The corrosive medium Cl was found in the scale composition detection, and no obvious corrosive medium was found in the corrosion products of the fracture surface.
One of important strategies to improve the ranges of battery electric vehicles is to develop and apply batteries with high energy density. Lithium-rich layered oxide cathode material is one of the most important methods to improve the energy density of batteries. However, there are two bottlenecks in the material: the voltage attenuation of structural transformation and the violent electrolyte decomposition on high voltage. In this study, a spherical Li1.2Mn0.54Co0.13Ni0.13O2 cathode material (LLO) was investigated. The cycle performance of the LLO cathode in various LiBOB electrolytes was compared. The metal dissolution on the positive electrode surface is reduced. Through theoretical calculation and X-ray photoelectron spectroscopy, the preferential combination of LiBOB and oxygen anion was verified, and the possible oxidation process of LiBOB in LLO cathode was speculated. Boron containing CEI film contained some unreacted BOB anion, half BOB structure (1B-O similar structure), alkyl borate, oxalate and lithium fluoride. The results of this study are helpful to understand the electrode / electrolyte interface chemistry of boron containing additives in lithium rich cathode.
The microstructure, macro morphology, oxide layer morphology and mechanical properties of T91 steel after 96000 hours of service at high temperature and high pressure were investigated. The results show that the service steel pipe has good macroscopic appearance, no obvious wear, scratch, bulge, deformation, surface crack and other abnormal features, and no obvious thinning of wall thickness. The chemical composition of different pipe sections meets the standard, and the microstructure is mainly tempered martensite, which is evenly distributed, with a small amount of massive ferrite and no obvious coarse phase. The oxidation products are divided into internal oxide layer and external oxide layer, and the internal oxide layer is dense and continuous, microcracks appear in the loose oxide layer. After 96000 hours of service, T91 steel has good mechanical properties. The tensile properties at room temperature and high temperature are good. For room temperature, the yield strength and tensile strength are 480MPa and 630MPa, respectively. Under 500°C and high temperature, the yield strength exceeds 319MPa, the tensile strength exceeds 380MPa, and the elongation exceeds 17%. Hardness test values are between 185∼250 HBW.
The high cost and negative environmental impact of traditionally made aluminium metal matrix composites (AMMC) need their replacement with eco-friendly materials with improved mechanical characteristics. The repurposing of agricultural waste in innovative materials is critical to achieving a sustainable society. This study utilized AA6061/chitosan at sieve size of 90¸tm created via modified stir casting at weight proportions of 3, 6, 9, and 12 wt. %. The produced composites reached a maximum hardness of 60.2 HRB at 9wt. % chitosan, comparable to a 2.36 % improvement in AA6061 hardness, 57.4 HRB. Similarly, tensile strength increased with increasing chitosan particles, from 83.07MPa for the unreinforced alloy to a maximum of 114.92MPa for 12 wt. % AA6061 reinforcement with chitosan. The samples’ XRD revealed clear evidence of Hydroxyapatite, Ca10(PO4)6(OH)2, a component of teeth and bones that provides strength. The corrosion characteristics findings reveal that AA6061+9 wt. % chitosan has the lowest corrosion rate of all the samples. In addition, the microstructure of AA6061 with chitosan strains of reinforcement was observed in the AA6061/3wt. % SEM, eventually filling grain boundaries of the metal with increasing reinforcements to provide evenly distributed fibrous links connecting AA6061 grain structure at 6wt. % and 9wt. % reinforcement in the micrograph
The welded joint of TC4 titanium alloy is easy to form coarse grain, and there is a large residual stress and residual deformation after welding. By applying ultrasonic aid in the conventional TIG welding process, the ultrasonic amplitude converter is directly contacted with the TC4 titanium alloy plate, and the ultrasonic cavitation effect generated by ultrasonic vibration and the mechanical vibration stirring effect are used to influence the flow and solidification process of liquid metal in the weld pool, so as to refine the microstructure and grain of the weld and reduce the residual stress of the weld. The grain size and residual tensile stress of welded TC4 titanium alloy joints under different ultrasonic power were measured. Compared with conventional TIG welding, the average grain size of the weld is reduced by 22.70 % and the average residual stress release rate is 82 % when 2000 W ultrasonic power is applied. Grain refinement can increase grain boundary number and improve material strength. Reducing the residual stress of weld can further reduce the fatigue crack propagation rate of weld. Therefore, it is of practical significance to improve the weld microstructure and reduce the residual stress of welded joints by ultrasonic assisted welding technology to improve the strength and reliability of welded structures.
In practice, wet and submerged repair and reinforcement is often encountered, such as damage to tunnels due to wear and tear and water erosion, leakage in concrete diversion channels, etc. Due to the presence of large amounts of water in the environment, it is very difficult to achieve dry conditions for repair and reinforcement of such structures, which often requires wet or submerged construction. In addition, dams are subject to cracks and surface peeling in submerged concrete or reinforced concrete due to the complex environment they have been in for a long time, and concrete is also subject to pressure water due to dam storage. Conventional repair materials pursue high groutability, good flowability of the slurry but it is extremely easy to disperse when it encounters water scouring, failing to achieve the effect of grouting, wasting material seriously and washing away lost material will also cause pollution to the environment. As the mountain is relatively fragmented, the grouting process consumes a large amount of grout, so it is necessary to keep the grouting within certain limits. Therefore, the specific grouting construction conditions also place special requirements on the grouting material, towards the need for grouting material to meet the premise of groutability and mechanical properties, but also the need to meet the construction requirements of underwater or moving water conditions, as well as the control requirements of the grout flow range. This paper introduces a controlled grouting material which, by regulating the setting time and viscosity of the material, allows the grouting material to be well adapted to grouting under local subsurface moving water conditions.
The development of high-voltage electrolyte system is a key factor in the commercialization of high-voltage spinel lithium nickel manganese oxide (LNMO) battery materials. This article carries out the optimization and exploration of LiBOB electrolyte additives in high voltage LNMO cathode materials. The test results show that the performance is best when the electrolyte is added at 30–50 μL. In order to study the mechanism of LiBOB on the LNMO anode, combining the characterization results of XRD, XPS, IR, Raman, and electron microscopy, it can be seen that LiBOB is preferentially oxidized and a layer of boron-rich CEI film with a thickness of about 8 nm is formed on the surface of the LNMO anode. This passivation film physically blocks the contact between the electrolyte and the surface of the highly active electrode, maintains the stability of the LNMO structure under high voltage, and improves the electrochemical performance.
Aviation stainless steel 0Cr17Ni4Cu4Nb has excellent properties and is widely used in important parts of various machinery. The equivalent static compression test and impact test of 0Cr17Ni4Cu4Nb aviation Martensitic stainless steel at normal temperature were followed out by a universal test machine (UTM5305) and a high temperature separation Hopkinson test facility, respectively. The equivalent static compression data of 0.001, 0.01 and 0.1 s-1 at 25°C and the dynamic stress-strain data of 25, 350, 500 and 650°C at 25°C and the authors got strain rates of 750, 1500, 2000, 2600, 3500 and 4500. According to them, a Johnson Cook (JC) modified constitutive model was built and its prediction accuracy was confirmed. The consequences indicate that the correlation of association (R) is 0.987513 and mean relative error (AARE) of the revised JC constitutive equation is 0.51%, which indicate that the revised JC constitutive equation is a little accurate and reliable. When they are in high strain rates, generally speaking, they can predict its stress-strain connection.
In the current study, the evolution of S(Al2CuMg) phase in a commercial Al-Zn-Mg-Cu alloy during homogenization, deformation and solution treatments was investigated and the effect of residual S(Al2CuMg) phase on mechanical properties in finished plates was revealed. The results showed that S(Al2CuMg) phase formed during solidifications and existed in eutectic structure. Parts of AlZnMgCu phase transformed to S(Al2CuMg) phase after the first homogenization treatment with a regime of 470°C/24h. During the second homogenization treatment at 480°C, most of the S phase had gradually dissolved. However, a handful of large-sized S phase remained even after extending the second stage homogenization time to 48h. During deformation these remaining S(Al2CuMg) phase was broken, resulting in size reduction and apparent distribution along the rolling direction, which could be effectively eliminated by a two-stage solid solution regime of 470°C/1.5h+480°C/2h. Comparing the microstructure and properties of final plates treated by homogenization processes, it was evident that the alloy subjected to a single-stage homogenization treatment exhibited a significantly higher amount of residual S phase, which directly compromised fracture toughness but has a relatively minor impact on strength.
In this work, locally sourced organic wastes were used to produce brake pad using Taguchi experimental design. Organic wastes selected for production include seashell and snot apple fiber while graphite, ceramic wastes and araldite were used as friction modifier, abrasive and binder respectively. Nine samples were produced using Taguchi design technique by varying percentage composition and adopting constant process parameters. Sample characterization was carried out by investigating the tribological properties (wear rate and friction coefficient). The experimental findings revealed that optimal wear rate of the developed brake pad can be obtained using seashell (105.5g), snot apple fiber (4.5g), araldite (50g), ceramic (24g) and graphite (22g) while the optimal friction coefficient can be obtained using seashell (96g), snot apple fiber (4g), araldite (40g), ceramic (20g) and graphite (22g). Based on the results obtained, it can concluded that the selected organic wastes can effectively serve as reinforcement materials in the production of brake pads.
The hard phase added into the laser-cladding layer will be melted a lot with its size reducing or even disappearance because of rapidly heating of the laser beam with high power density during laser cladding, resulting in the properties of the laser cladding layer decreased. In order to regulate the hard phase size in the laser cladding layer, the surface modification of titanium carbide (TiC) by chemically clad cobalt (Co) was used to improve the expected performance after laser cladding. The mixing powder of Co-based alloy with the TiC powder of 40–60 μm, which the ratios among the Co-based alloy, Co-coated TiC and TiC powder are 7:3:0, 7:3:3, and 7:0:3, was clad to the surface of QT600-3 ductile iron substrate using a fiber laser, respectively, to obtain the cladding layer of 4mm thick by three sub-layers of cladding. Laser cladding process parameters are: laser power P=1.2kW, scanning speed of 320mm·min-1, spot diameter of 3mm, lap rate of 1.5 between two passes. The variation of the micro-structure, second phase and hardness of the cross-section of the layer was analyzed by Olympus metallographic microscope (OM), scanning electron microscope (SEM) observation with energy diffraction spectrum (EDS) and Rockwell hardness tester. The results show that the clad layer is well formed on the surface without cracks, pores and other defects and well bonded with the substrate. There exist a large number of TiC hard phases in the microstructure with a little difference of the TiC size compared with the raw material powder, because the melting of TiC under the laser beam is reduced after the TiC clad with Co. So, the hardness of the cladding layer was improved compared with the ratio of 7:0:3 and increased rapidly and then gently with the increase of the distance from the surface of the ductile iron substrate. Under the condition of 7:3:3 powder ratio, there appears a large amount of new dendritic TiC phase in the microstructure, where the grains were refined, and the maximum hardness of the clad layer was obtained with 64.5 HRC.