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2022 Vol. 65, No. 15
Published: 2022-08-01
FEATURE
FORUM
RESEARCH
C0NTENTS
COVER STORY
 
1 COVER
2022 Vol. 65 (15): 1-1 [Abstract] ( 24 ) HTMLNew PDF (6294 KB)  ( 23 )
       C0NTENTS
6 CONTENTS
2022 Vol. 65 (15): 6-10 [Abstract] ( 44 ) HTMLNew PDF (426 KB)  ( 19 )
       FEATURE
14 Simulation for Shot Peening Strengthening Deformation of Thin-Walled Parts With Multiple Random Shots
ZHOU Wenlong，WANG Miao，SUN Yifan，LI Zhiqiang，CHEN Guoqing，FU Xuesong
DOI: 10.16080/j.issn1671-833x.2022.15.014
The deformation characteristics of thin-walled parts during shot peening are simulated by the coupled finite and discrete element methods (FEM–DEM). A shot peening strengthening model with multiple random shots based on Almen strip is established and verified by shot peening test. The flat, straight and thin-walled specimen in the model warps upward in arc shape after random shot peening. The deformation characteristics are consistent with the actual shot peening deformation of Almen strip. When the shot peening pressure increases from 0.07 MPa to 0.11 MPa, the simulated arc height increases from 0.340 mm to 0.521 mm, and the simulation accuracy of arc height can reach 95%; The residual stress field introduced by random shot peening on the surface of Almen strip shows an S-shaped barb distribution along the depth direction. With the increase of shot peening pressure, the simulated surface residual compressive stress increases from about –400 MPa to about –700 MPa, and the maximum error comparing with the test results is 11.31%; The surface roughness Ra of Almen strip rises with the increase of shot peening pressure, and the simulated roughness value increases from 0.476 μm to 0.630 μm, and the maximum error of simulation is 6.78%. Through comparison and verification, the simulation results of the model are in good agreement with the shot peening test results. FEM–DEM coupled random shot peening model can better simulate the variation law of deformation, residual stress field and roughness of thin-walled parts.
2022 Vol. 65 (15): 14-22 [Abstract] ( 127 ) HTMLNew PDF (29408 KB)  ( 57 )
       COVER STORY
24 Research Status of Atmospheric Plasma Spraying YSZ Thermal Barrier Coating Internal Stress
ZHAO Yuantao，ZHANG Shitao，JIANG Tao,GUO Leyang，ZHANG Yangyang，LI Wenge，LIU Yanbo，ZHANG Jing
DOI: 10.16080/j.issn1671-833x.2022.15.024
The preparation of yttrium-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) using atmospheric plasma spraying (APS) has been extensively investigated. Internal stress is a major factor affecting the performance and service life of TBCs systems. Excessive internal stresses can cause the development and expansion of microcracks and lead to premature failure of YSZ TBCs. Early internal stresses are mainly caused by poor selection of the coating process, substrate and powder conditions, and cause early crack initiation and extension. High temperature phase changes in ZrO2 , thermal growth oxide (TGO) growth and coefficient of thermal expansion (CTE) mismatch between ceramic and metallic materials are the main sources of internal stresses in TBCs in thermal service. Under internal stress, cracks sprout at the surface ceramic working layer (TC)/TGO or bonding layer (BC)/TGO interface, expand and lead to coating peeling failure. The main ideas to reduce the internal stresses in the system in order to extend the thermal service life of TBCs are to interfere with spinel TGO generation, to prepare composite coatings or to stabilise the ZrO2 phase structure with rare earth particles.
2022 Vol. 65 (15): 24-32 [Abstract] ( 115 ) HTMLNew PDF (9702 KB)  ( 59 )
       FORUM
36 Effect of Rare Earth Content on Microstructure and Hardness of Laser-Caldded Mo2FeB2 Cermet
SUN Junsheng，XU Hu，GUAN Changyong，WANG Dezhu，SHI Bin
DOI: 10.16080/j.issn1671-833x.2022.15.036
The preparation of Mo2FeB2 cermet by vacuum sintering technology causes a large initial investment for equipment, low production efficiency, high cost and poor adaptability for engineering applications. In order to overcome these disadvantages, the Mo2FeB2 cermet can be prepared by laser cladding. In this paper, the effects of RE(Rare earth) mass fraction on the microstructure and properties of cladding metal were studied by means of scanning electron microscope (SEM) and hardness tester. It was found that the hard phase of the claddings with 2% RE addition was obviously refined compared with that without the addition of rare earth. With the further increase of rare earth addition, the hard phases began to agglomerate and connect with each other. Adding rare earth can make more Cr element replace Fe element in Mo2FeB2 . The replacement is more at addition of 2% RE , is the most at the addition of 8% RE, and is less at the addition of 4% RE. As for the claddings with 0, 2%, 4% and 8% RE added, the area fractions of the hard phase were 30.84%, 53.74%, 71.25% and 54.92%, respectively, and the average microhardness were 627HV, 923HV, 1008HV and 742HV. These results suggest that the area fraction of the hard phase and the hardness of the claddings are significantly improved with the addition of RE.
2022 Vol. 65 (15): 36-40 [Abstract] ( 66 ) HTMLNew PDF (15513 KB)  ( 57 )
41 Effect of Gradient Microstructure on Mechanical Properties After Surface Strengthening of Metals
QIN Zhi, LI Bin, ZHANG Han, XUE Hongqian
DOI: 10.16080/j.issn1671-833x.2022.15.041
Materials with a gradient microstructure after surface strengthening have received a lot of attention due to their excellent mechanical properties. This paper reviews the preparation of gradient microstructures, their effects on mechanical properties (strength-plasticity, work hardening, friction wear and fatigue properties). Firstly, the mechanism of gradient microstructure formation and preparation methods are summarised according to the different principles of process preparation. Secondly, recent progress in the study of the mechanical properties of gradient microstructures (strong plasticity, work hardening, friction wear) and the analysis of the enhancement mechanism are summarised, while the anomalous test phenomena are explained. The reasons for the improvement of low and high cycle fatigue properties of metallic materials are comprehensively analyzed from the aspects of the gradient microstructure and residual stresses formed after surface strengthening. Finally, some of the current problems faced by gradient microstructure metals and future research directions are pointed out.
2022 Vol. 65 (15): 41-50 [Abstract] ( 72 ) HTMLNew PDF (16799 KB)  ( 24 )
51 Study on Surface of Nickel Base Superalloy Strengthened by Coupled Ultrasonic and Electric Pulse With Water-in-Oil Working Fluid
JIN Hui, JI Renjie, WANG Baokun, LIU Yonghong
DOI: 10.16080/j.issn1671-833x.2022.15.051
In this paper, a new type of water-in-oil (W/O) emulsion suitable for coupling electrical pulse and ultrasonic treatment was developed, and the influence of water content on the viscosity and conductivity of the W/O emulsion was explored. It is found that when the water content is 40% and below, the W/O emulsion can maintain low electrical conductivity, have excellent dielectric properties, and better flow properties. Inconel 718 alloy was treated with water, W/O emulsion with mass fraction of 20% and 40%, and the surface morphology, wear resistance and corrosion resistance after treatment were investigated. The results showed that the surface of the sample treated with W/O emulsion with mass fraction of 40% is the smoothest, and has the best wear resistance and corrosion resistance. Compared with the substrate, the friction coefficient is reduced by 0.267, the wear loss is reduced by 43.2%, the corrosion current density is reduced by 86.9%, and the impedance is increased by 45.4%. The W/O emulsion can effectively fill the gap between the carbon brush and the sample, avoid the occurrence of discharge phenomenon. At the same time, the W/O emulsion can provide excellent lubrication effect, which can weaken the friction between ultrasonic vibration head and sample surface, and finally obtains better surface quality.
2022 Vol. 65 (15): 51-58/63 [Abstract] ( 50 ) HTMLNew PDF (18127 KB)  ( 21 )
59 Comparative Study on Plasma Complex Treatment and Plasma Nitriding
SUN Fei，LU Yangyang，HU Jing
DOI: 10.16080/j.issn1671-833x.2022.15.059
In order to take advantage of the individual advantages of plasma nitriding and plasma nitrocarburizing, and overcome their shortcomings, plasma complex treatment combining both plasma nitrocarburizing and plasma nitriding (hereinafter referred to as complex treatment) was developed and compared with a single plasma nitriding. The nitrided layer thickness, phase microstructure, cross-sectional microhardness were investigated by means of optical microscope, X–ray diffraction and microhardness tester. The results show that the compound layer thickness after complex treatment is much thicker than that after plasma nitriding, thus the nitriding efficiency is improved remarkably. Fe3C phase was occurred in compound layer after complex treatment, and the dominated phase of the compound layer was transformed from γ′ to ε phase. Higher microhardness was obtained after a complex treatment. In addition, activation energy (Q) of forming compound layer decreases from 179.7 kJ/mol in plasma nitriding to 87.1 kJ/mol for the complex treatment. And the kinetics of plasma nitriding and complex treatment in the temperature range of 783 K to 843 K was obtained as the following formula dplasma nitriding=exp（15.8–10810/T）, dcomplex treatment=exp（9.7–5237/T）.
2022 Vol. 65 (15): 59-63 [Abstract] ( 58 ) HTMLNew PDF (13319 KB)  ( 16 )
64 Effect of Surface Texturing-Plasma Surface Chromizing Duplex Treatment on Wear Resistance of TA2 Pure Titanium
LIN Naiming，LEI Xin，WANG Huanhuan，YUAN Shuo，WANG Qiang，LEI Chenqing，YAN Jiangshan，WANG Weihua，MA Guanshui，ZENG Qunfeng
DOI: 10.16080/j.issn1671-833x.2022.15.064
A chromium modified layer was prepared by laser surface texturing-double glow plasma surface alloying duplex treatment to improve the wear resistance of TA2 pure titanium. And the tribological behavior of the duplex treated sample at room temperature and 600 ℃ was investigated. The results showed that the continuous and dense chromium layer was fabricated using plasma alloying technology on the surface of TA2 with uniform circular texture unit. The thickness of the chromium layer was 55 μm, which is mainly composed of solid solution and CrTi and Cr2Ti compound phases. Chromizing treatment significantly improved the surface hardness of TA2. The laser surface texturing-plasma surface chromizing duplex treatment significantly improved the wear resistance of TA2 at room temperature and 600 ℃ . In terms of mass loss, the duplex treated sample was reduced by 77.2% and 75% compared to the TA2 matrix at room temperature and high temperature respectively.
2022 Vol. 65 (15): 64-74/81 [Abstract] ( 49 ) HTMLNew PDF (22124 KB)  ( 23 )
75 High Temperature Corrosion Resistance of Wet Grit Blasted AIP AlSiY Coating
LI Hanyun，WANG Bo，PENG Xin，YANG Lin，YUAN Fuhe
DOI: 10.16080/j.issn1671-833x.2022.15.075
AlSiY coating was deposited on the directionally solidified DZ22 superalloy using an arc ion plating technique in an aim to resolve or alleviate the high temperature corrosion damage of high pressure turbine blades for aero-engines and gas turbine engines. The attained results demonstrate that the AlSiY coating deposited and vacuum diffusion heat treated at a high temperature consists of an outer, an intermediate and a thin inner diffusion layer, which is typical of a high activity aluminide diffusion coating composed of the single β–NiAl intermetallic phase. The results of thermogravimetric analyses and examinations of cross sections demonstrated that the wet grit blasting process improves significantly the corrosion resistance of the AlSiY coating under salt film and hot-gas conditions. A thick oxide scale developed on the as-diffusion heat treated coating consists primarily of Al2O3 and NiAl2O4 corrosion products under salt film and hot-gas corrosion conditions, and most of the coating degenerated into the γ′–Ni3Al phase with some pores formed inside. Wet grit blasting of the heat treated AlSiY coating is desirable to promote the selective oxidation of aluminium, chromium elements and formation of a thin, denser alumina scale under both corrosion conditions, thereby enhance remarkably the high temperature corrosion resistance and prolong the service life of the arc ion plated AlSiY coating.
2022 Vol. 65 (15): 75-81 [Abstract] ( 63 ) HTMLNew PDF (13161 KB)  ( 20 )
       RESEARCH
82 High-Speed Milling Process of Aircraft Large-Scale Aluminium Alloy Integral Wall Panel
WANG Wenli, SHAO Kun, LUO Rui, YAN Wei, CHANG Chang
DOI: 10.16080/j.issn1671-833x.2022.15.082
The aircraft large-scale aluminum alloy integral wall panel has several characteristics such as thin walls, weak rigidity, and difficult locating and clamping during the CNC machining. It is difficult to ensure wall thickness and weight tolerance. It is a typical type of difficult-to-machining aircraft structure parts. This paper studies the high-speed milling technologies dealing with aircraft large-scale aluminum alloy integral wall panel, analyzes the structure characteristics of the panel, designs the fabrication order and programming strategy about the panels and supporting embosses in the rough machining operations, uses the vacuum fixture, adjusts the dimension of thickness and takes two times finish machining by the adaptive machining method of the measurement and adjustment integrated, which can keep the thickness and weight tolerance effectively.
2022 Vol. 65 (15): 82-86/110 [Abstract] ( 112 ) HTMLNew PDF (20324 KB)  ( 221 )
87 Simulation Study on Surface Quality of Titanium Alloy in Elliptical Ultrasonic Vibration-Assisted Machining
CHEN Dexiong, JING Xuqin
DOI: 10.16080/j.issn1671-833x.2022.15.087
Elliptical ultrasonic vibration-assisted machining(EVAM) technology is an effective method to improve the processing quality of difficult-to-cut materials. The aim of the present study was to develop a finite element model in order to investigate the effects of ultrasonic vibration parameters (frequency and amplitude) on the machining residual stress and surface morphology of Ti6Al4V. The results of finite element analysis showed that ultrasonic vibration-assisted cutting could increase the maximum residual compressive stress distribution depth, but would deteriorate the surface morphological integrity of the workpiece. The Y-directiona vibration impulse impact load on the surface of the workpiece was conducive to increase the residual compressive stress field of the workpiece. The morphological integrity of the workpiece surface gradually improved with the increasing of vibration frequency and X-direction amplitude, and deteriorated with the increasing of Y-direction amplitude. Increasing the vibration frequency and amplitude was beneficial to the formation of residual compressive stresses on the workpiece surface and improve the machining quality of the workpiece.
2022 Vol. 65 (15): 87-94 [Abstract] ( 74 ) HTMLNew PDF (2047 KB)  ( 202 )
95 Finite Element Simulation of Preload Process and Mechanical Properties of Connection#br# Structure of Low Interstitial Ti–6Al–4V Shear Bolt
YIN Yinyin，GAO Xuemin，FENG Derong，DONG Chenxi，LIU Qianfeng，WU Xiaozhong
DOI: 10.16080/j.issn1671-833x.2022.15.095
Bolt connections are widely used in the mechanical industry. For the performance of low clearance Ti–6Al–4V ELI hexagonal head bolts in service in the connection structure, a 3D finite element model of single-lap bolted connection structure considering thread details was established based on ABAQUS finite element simulation software. The Ti–Ti and Ti–Al bolting models were established to simulate the two analysis processes of preload and tension of the bolt connection structure. The Ti–6Al–4V ELI material parameters were verified by comparison of tensile tests and finite element simulation result. The loading curve of the bolt preload force, the load capacity curve of the bolt connection structure and the stress distribution state of the bolt connection structure during preload and tension were obtained by finite element simulation, and the influence of the bolt preload force on the mechanical properties of the bolt connection structure was investigated.
2022 Vol. 65 (15): 95-102 [Abstract] ( 59 ) HTMLNew PDF (52570 KB)  ( 49 )
103 Microstructure and Mechanical Properties of Ti6242 Titanium Alloy Joints by Electron Beam Welding
SUI Nan, ZHOU Yi, ZHANG Mingda, CAO Jingxia, HUANG Xu
DOI: 10.16080/j.issn1671-833x.2022.15.103

Three electron beam welding processes were used to obtain the welded joints of Ti6242 titanium alloy. The microstructure and mechanical properties of electron beam welded joints of Ti6242 titanium alloy were studied by means of microstructure analysis, tensile and impact property tests, fractography analysis and so on. Results show that the electron beam welded joint of Ti6242 titanium alloy consists of base metal zone, heat affected zone and weld fusion zone. The heat affected zone can be divided into equiaxed grains area, incomplete–β area and nearly complete–β area. The microstructure of the weld fusion zone is composed of β–columnar grains with a small amount of β–equiaxed grains distributing in the center. The acicular martensite α′ phase was found both in the weld fusion zone and heat affected zone. With reasonable control of welding heat input, Ti6242 titanium alloy can obtain favorable welded joints with higher strength, slightly lower plasticity and lower impact property than the base metal. The tensile fractography shows dimple morphology and its fracture mechanism is micropore aggregation plastic fracture. The impact fractography is characterized by a mixture of dimples and quasi-cleavage, simultaneously many small dimples and tearing edges distribute between the columnar fracture surfaces. The fracture mechanism is a mixture of micropore aggregated fracture at the dimple and slip band fracture on the quasi-cleavage plane.
2022 Vol. 65 (15): 103-110 [Abstract] ( 78 ) HTMLNew PDF (98451 KB)  ( 42 )
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