In recent years， with the rapid development of industries such as new energy vehicles， aerospace， and high-end equipment manufacturing， along with the integration of technologies like artificial intelligence and big data， machine tools are advancing toward higher levels of high-end，intelligent，and green technologies.Cutting fluids are essential for achieving efficient，precise，and low-cost metal cutting processes.However， with the rapid growth of the machinery manufacturing industry， the conflict between the low performance of traditional cutting fluids and the high-quality manufacturing requirements of core components has become increasingly evident.On the other hand， the green application and safe disposal of cutting fluids have become major obstacles to the green development of the industry.Therefore， addressing the series of issues associated with traditional cutting fluids is a critical research topic faced by both the machinery manufacturing industry and the environmental protection field.This paper took the limitations of traditional cutting fluids as the starting point， and organized the current research on cutting fluids from three dimensions: environmental protection， economy， and functionality.The latest research progress on lubrication and cooling mechanisms， process effects， and parameter optimization was reviewed， and the advantages and disadvantages of different cutting fluids， along with the issues encountered during their development， were analyzed.Finally， from the perspective of industrial practical applications， the paper provided an outlook on metal cutting fluids and offered theoretical insights and research directions for the functionalization and greenization of cutting fluid technology， aiming to promote the domestic substitution of cutting fluid technologies in China.

Pipeline is a relatively safe major transportation mode for oil，natural gas and other energy media，but due to the long laying distance of crude oil pipelines， the complexity of the internal fluid environment， and the fact that the transportation medium has a certain corrosiveness，corrosion leakage accidents occur frenquenfly in crude oil pipelines， which seriously affects the daily production management of pipelines.Online monitoring of pipeline internal corrosion is an effective means to obtain the corrosion status of pipeline immediately and accurately and ensure the safe operation of crude oil pipeline.The study of corrosion type and mechanism of crude oil pipeline can provide a good reference for the improvement of on-line monitoring technology.This paper discussed the types and mechanisms of internal corrosion in crude oil pipelines as well as the widely used pipeline internal corrosion monitoring technologies， analyzed and compared the advantages and disadvantages of various online pipeline corrosion monitoring technologies and their application scenarios.Furthermore， the prospects for the selection， improvement and development of online pipeline corrosion monitoring technologies were put forward.In general， it’s pointed out that the online monitoring technology of pipeline internal corrosion will develop in the direction of intelligence， automation and remote monitoring in the future， which provided valuable references for relevant researchers and enterprises to carry out on-site innovative applications.    

Aluminum alloys are widely used in the field of marine engineering owing to lightweight and excellent corrosion resistance.However，the complexity and severity of the marine atmospheric environment can lead to serious corrosive damage to aluminum alloy components.The corrosion behavior and regularity of typical aluminum alloy 2A12 and 5A02 under simulated tropical coastal atmospheric environment were studied by indoor cyclic salt spray accelerated test.The corrosion micromorphology， corrosion product composition and electrochemical behavior of samples with different cyclic periods were analyzed and compared with outdoor exposure test.In addition， the correlation between the results of outdoor environmental exposure test and indoor accelerated test was quantitatively analyzed by grey relational method.Results showed that the relationship between corrosion weight loss and time of 2A12 and 5A02 samples conformed to the law of power function.After the test， obvious pitting corrosion occurred on the surface of aluminum alloy， and the corrosion products primarily consisted of Al2O3 and AlO(OH).With the extension of the test time，the pitting degree of aluminum alloy was deepened，and the number and depth of pitting pits increased.Meanwhile，the number and depth of pitting pits on the surface of 5A02 aluminum alloy were lower than that of 2A12 aluminum alloy.The electrochemical impedance fitting results also showed that the corrosion resistance of 5A02 aluminum alloy was better than that of 2A12 aluminum alloy with the increase of cycle acceleration period.By comparing the results of outdoor test and indoor test，it could be concluded that indoor cyclic salt spray acceleration test could simulate the results of outdoor exposure tests well， and reflect the corrosion behavior and law of aluminum alloy well in terms of pitting depth change and weight loss dynamics.However，the simulation correlation would decrease with the extension of exposure time.Overall， this study provides basic test data for optimizing the correlation between indoor accelerated corrosion test and outdoor exposure test of typical aluminum alloys.

Hydroxylammonium nitrate (HAN)-based propellant is a new type of green propellant.The compatibility of HAN-based propellants with traditional aerospace structural materials， such as titanium alloys， requires further investigation.The corrosion behavior of TC4 titanium alloy in HAN-based propellant was studied over long periods using electrochemical noise (EN) methods， along with scanning electron microscopy (SEM)， X-ray photoelectron spectroscopy (XPS)， and other analytical techniques.Results showed that， with the extension of immersion time， the average values of potential noise and current noise reflected the process of active corrosion-oxide film formation-corrosion equilibrium occurring in both the base material and welded material samples.Moreover， the standard deviation of potential noise in both base material and welded material reached its maximum on the first day of immersion，at values of 5.92 and 6.02，respectively.The standard deviation of potential noise in the welded material was slightly higher than that in the base material， indicating a slightly higher corrosion activity in the welded material.During the 65 d immersion of TC4 in alkaline HAN-based propellant， the slope of the power spectral density (PSD) curve in the highfrequency region remained at approximately－1 dB/dec， far greater than－20 dB/dec， which was consistent with the strong localized corrosion behavior of TC4 alloy in alkaline HAN-based propellant.The alloy element Al in TC4 formed Al2O3 and Al(OH)3 on the surface during the corrosion process in HAN-based propellant， while the oxide of the alloy element Ti reacted with the alkaline HAN medium to form soluble salts， preventing the formation of a stable and dense passivation film on TC4 titanium alloy in alkaline HAN-based propellant.

In order to further develop steel wires with high strength and corrosion resistance for ultra-deep oil well load detection cables，Zn-5Al alloy-coated steel wires were studied.The effects of cold drawing strain on microstructure， mechanical properties and corrosion resistance of coated steel wire were studied by means of scanning electron microscope， X-ray diffraction， electronic universal testing machine，electrochemical workstation and other instruments.Results showed that during the drawing process，the pearlite structure changed from equiaxed to fibrous along the drawing direction， with a gradual decrease in interlamellar spacing and a reduction in coating thickness.When the drawing strain exceeded 2.24， the tensile strength exceeded 2 400 MPa， meeting the requirements for steel wire used in the armoring of 10 000-meter oil well load detection cables.The results of dynamic polarization curves and full immersion tests showed that as the strain increased， the corrosion resistance of the Zn-5Al coated steel wire improved， and the corrosion rate decreased.The neutral salt spray corrosion test indicated that，in terms of long-term corrosion (506 h)， the best corrosion resistance was achieved with a strain value of 1.19， where the corrosion rate was 0.104 7 g/(m2∙h).The corrosion products mainly consisted of Zn6 Al2(OH)16 CO3 ∙4H2 O， Zn5(OH)8 Cl2 ∙H2 O， and small amounts of loose ZnO and Zn5(CO3)2(OH)6.After cold drawing deformation， the corrosion products became finer and denser， enhancing their protective effect on the substrate.Cold drawing deformation not only increased the strength of the steel wire but also effectively improved the corrosion resistance of the coated steel wire.

To improve the mechanical properties and wear and corrosion resistance of 921A steel surface under marine environment， two kinds of coatings were prepared on the surface of 921A steel by supersonic plasma spraying technology.The powders used were NiCrBSi spherical powder and NiCrBSi composite powder with chromium plated diamond (20～40 μm).The prepared coating samples were labeled as coating N and coating ND respectively， and the spray substrate was labeled as sample 921A in the subsequent comparison test.Moreover， the phase composition of the coating was analyzed，the cross section morphology and element composition of the coating were observed，the microhardness and tensile bond strength of the coating were tested， the friction coefficient and volume wear rate of the coating with Si3N4 ball under the reciprocating friction and wear mode were measured， and the open circuit potential and self-corrosion current density of the coating were fitted.Results showed that compared with the coating N prepared by pure NiCrBSi powder， the microhardness and bonding strength of diamond composite coating ND were 1 016 HV and 50.156 MPa， which were 15.3%and 15.3%higher than those of coating N.Under the condition of 30 N load，Si3N4 ball as the grinding object and reciprocating time of 60 min， the average ND wear depth of diamond composite coating was 17.738 μm，exhibiting a 75.8%decrease relative to the substrate.The volume wear rate was 1.40×10－5 mm3/(N∙m)， which was only 20.7%of the substrate， and the friction coefficient was 0.229.At room temperature and 3.5%NaCl solution，the ND self-corrosion potential Ecorr of the diamond composite coating was－864 mV， which was 61 mV higher than that of the 921A substrate， and the self-corrosion current density Jcorr was 1.332×10－5 A/cm2， which was 77.9%lower than that of the 921A substrate.

To evaluate the high temperature application range of SHM1302 hard surface layer， the thermal shock resistance and high temperature wear resistance of SHM1302 hard surface layer were tested respectively， and the thermal shock and high temperature wear behavior of hard surface layer were investigated by X-ray diffraction (XRD)， scanning electron microscopy (SEM)， energy dispersive X-ray spectroscopy(EDX) and other characterization methods.In addition， the relationship between high-temperature oxidation / microstructure transformation and thermal shock / high-temperature wear behavior was established.Results showed that the initiation and propagation of SHM1302 thermal shock cracks were affected by the combined effects of stress and oxidation， and the cracks mainly propagated along the interface between matrix and carbide.With the thermal shock cycle，the formation of harmful phase of MnFe2O4 in the oxide film and the precipitation of (Fe，Cr)3C in the matrix promoted the expansion of thermal shock cracks.At 500 ℃， the hard surface had good high temperature wear performance.The wear at 600 ℃and 700 ℃was significantly increased by 1 244%and 1 596%compared with 500 ℃.When the wear temperature increased from 500 ℃to 600 ℃， the increase of oxidation rate and the formation of harmful phase MnFe2O4 were the key factors for the rapid decline of wear performance.Furthermore， the M ⇌A structure transformation at 700 ℃promoted the initiation of fatigue cracks and further accelerated the wear process.

The loosening of fasteners has an important impact on the safety of subway and other rail transit.Aiming at the anti-loosening performance of GB/T 5782，M16×80，10.9 class Dacromet plated hexagon fastening bolts，the effects of lubrication state of fasteners on anti-loosening performance， wear behavior and corrosion resistance were investigated through lateral vibration anti-loosening test and neutral salt spray test.Results showed that when the preload force was set to 76 kN， the residual preload force of non-lubricated fasteners was more than 95%of the initial preload force for 1 500 vibration times，and the anti-loosening performance was excellent.Meanwhile，the anti-loosening performance of dacromet plated fasteners would be greatly attenuated by applying lubricants.When the preload force was set to 76，93，110 kN， the remaining preload force after 1500 vibration of the lubricated fasteners was less than 8%of the initial preload force.When the preloading force was set to 110 kN， the average residual preloading force after 200 times of vibration of the lubricated fasteners was 76.19%of the initial preloading force， which was higher that at 76 kN and 93 kN， but the residual preloading force of the late surface was not much different.In the process of vibration， the solid friction of the thread surface was transformed into solid liquid friction， and the relative friction was greatly reduced.When there was no lubrication， the fasteners were not loose， and the coating damage was light.Furthermore， the coating could protect the substrate from salt spray corrosion by sacrificial anode method of zinc ion， while the lubricant would loosen the bolts and produce a large relative movement between nuts and threads.The friction could destroy the surface coating and expose the carbon steel substrate of the fastener， causing corrosion under the condition of salt spray.

In order to inhibit the corrosion of pipeline steel during oilfield acidification，an imidazole-Schiff corrosion inhibitor (IAP) was synthesized.The corrosion inhibition performance and mechanism of IAP corrosion inhibitor with different concentration on P110 steel in 15%HCl solution were studied through weight loss and electrochemical tests.Subsequently，Fourier infrared spectroscopy (FTIR)，scanning electron microscopy (SEM) ＋energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to further confirm the inhibition mechanism of IAP on P110 steel in 15%HCl.In addition， the rationality of inhibition mechanism was further clarified from the molecular level by theoretical calculation.Results showed that when IAP added concentration was 400.0 mg/L，the weight loss test corrosion inhibition efficiency of P110 steel in 15%HCl was 97.58%， the test results of AC impedance spectrum (EIS) and potentiodynamic polarization (Tafel)curve showed that the corrosion inhibition efficiencies were 97.32%and 96.76%， respectively.EIS test results proved that IAP played a role in corrosion inhibition by forming film on the surface of P110 steel， and Tafel curve test results proved that IAP was a mixed corrosion inhibitor mainly based on anode inhibition.Meanwhile， the adsorption of IAP on P110 steel followed Langmuir isothermal adsorption equation and could be spontaneously adsorbed on the surface of P110 steel.FTIR，SEM＋EDS，and XPS successfully detected the protective film formed by IAP on the surface of P110 steel.Density functional theory (DFT) and molecular dynamics (MD) proved that the active sites of IAP were benzene ring and imidazole ring.Specifically，the benzene ring could accept excess electrons on the surface of Fe，the lone electron pair of N on the imidazole ring formed a stable coordination bond with Fe， and MD could further proved that IAP were spontaneously adsorbed on the surface of Fe.Overall，IAP corrosion inhibitor could demonstrate excellent corrosion inhibition performance in 15%HCl corrosive medium，with its mechanism involving the formation of a stable protective film on the surface of P110 steel.

In order to evaluate the effect of scratch defects on the stress corrosion performance of 690TT alloy heat transfer tubes in a simulated high-temperature and high-pressure water environment of the secondary circuit， a nuclear power steam generator heat transfer tube was chosen as the research subject.A scratch device was used to create C-ring specimens with scratch defects on the surface of the tube.The stress corrosion behavior of the scratched 690TT alloy heat transfer tubes was investigated in the simulated secondary circuit high-temperature and highpressure water environment.The surface defect morphology， oxidation morphology， distribution of oxide elements and surface profile of the specimens before and after corrosion were analyzed using scanning electron microscopy (SEM)， transmission electron microscopy (TEM)， energy dispersive spectrometer (EDS)，Raman spectroscopy and white light interferometer.Results showed that in the simulated secondary circuit high-temperature and high-pressure water environment， spinel oxide and chromium-rich oxide were formed on the surface of the C-ring scratch groove under stress loading.Additionally， the particle size and quantity of the spinel oxide on the outer surface increased with the test duration.The scratching process led to the formation of mechanical microcracks in the scratch groove area， but after long-term immersion， these microcracks did not show significant propagation， indicating that the scratched 690TT alloy has a high resistance to stress corrosion cracking in the secondary circuit simulated environment.

In order to clarify the influence mechanism of Cr diffusion barrier layer on the oxidation performance of NiCrAlY coating under high temperature conditions， NiCrAlY coatings and NiCrAlY-Cr composite coatings with Cr barrier layers of different design thicknesses (50， 100，150 μm) were prepared using plasma spraying technology.The phase composition changes of the coatings were analyzed using X-ray diffraction(XRD)， while the microstructure of the coatings was examined using scanning electron microscopy (SEM).The element distribution in the coatings and oxidation layers was analyzed by energy dispersive spectrometer (EDS) attached to the SEM.The high-temperature oxidation behavior of NiCrAlY-Cr coatings with different thicknesses of Cr barrier layers was investigated.Results showed that both the deposited NiCrAlY and NiCrAlY-Cr coatings were mainly composed of Ni3Al.After oxidation at 850 °C for 30 h， both NiCrAlY and NiCrAlY-Cr coatings formed α-Al2O3 and Cr2O3 on their surfaces.When the oxidation temperature was increased to 950 °C， after 30 h of oxidation， all three NiCrAlY-Cr composite coatings with different Cr barrier layer thicknesses showed a dominant Ni3Al phase on their surfaces， along with the formation of α-Al2O3， Cr2O3， and characteristic diffraction peaks of NiCr2O4.After 65 h of oxidation at 850 °C， the main phases in NiCrAlY and NiCrAlYCr composite coatings with different thicknesses of Cr barrier layers were α-Al2O3， Cr2O3， NiCr2O4 and Ni3Al.With the extension of oxidation time to 100 h， the phases in the NiCrAlY coatings and NiCrAlY-Cr composite coatings with Cr barrier layers of different design thicknesses remained dominated by α-Al2O3， Cr2O3， NiCr2O4 and Ni3Al after oxidation at both 850 °C and 950 °C.The dense protective layer formed by α-Al2O3， Cr2O3 and NiCr2O4 on the surface of NiCrAlY-Cr coatings in high-temperature environments provided significantly better high-temperature oxidation resistance compared to NiCrAlY coatings.

In order to address the surface quality and friction-wear issues of 7075-T6 aluminum alloy thin sheet in stamping forming， Electro Assisted Forming (EAF) technology was introduced into the stamping process.The effects of current densities ranging from 0 to 20 A/mm2 on the surface hardness， surface roughness and friction-wear behavior of the aluminum alloy thin sheet were studied and compared with the results of Hot Stamping (HS).A friction testing machine for EAF was used to simulate the forming process， and infrared thermography， Vickers hardness tester，shape measurement microscope，X-ray diffraction (XRD)，scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) were employed to observe and analyze the temperature， surface hardness， surface roughness， friction coefficient and wear behavior of the specimens.Results showed that， within the range of 0 to 16 A/mm2， the surface hardness of the EAF-processed specimens was higher and the surface roughness was lower than that of the HS-processed specimens at the same temperature.The enhancement of surface properties by electroplasticity at low current densities was attributed to the inhibition of the η′ metastable phase transition to the stable η phase.At high current densities， the Joule heat generated by electroplasticity caused significant softening of the thin sheet.The friction coefficient of the EAF specimens initially decreased and then increased with the rise in current density， reaching a minimum around 12 A/mm2.At this point， the friction coefficient of the EAF specimens was reduced by more than 10%compared to the HS specimens.After being processed by EAF at current densities ranging from 0 to 16 A/mm2， the specimens showed a lower wear rate， and a denser oxide layer was more easily formed on the surface， resulting in improved friction and wear resistance.

For investigating the optimal surface properties of thin aluminum-silicon coated steel plate after hot forming，the Al-10Si thin coated hot formed steel plate was taken as the research object， and the effects of different heat treatment temperatures on the microstructure and properties of the steel plate were studied by means of scanning electron microscopy， glow discharge emission spectrometer， micro-Vickers hardness tester， laser confocal microscope and friction and wear testing machine.Results showed that when the heat treatment temperature increased from 820 ℃to 930 ℃， the mutual diffusion of Al， Fe and Si progressively intensified.From the perspective of microstructure， the Fe-Al-Si phase in the coating，the diffusion layer between the coating and the steel substrate and the total thickness of the coating gradually increased，the martensite content in the substrate increased，and the shape showed a tendency of coarsening.From the element distribution，the diffusion extent of Al， Si and Fe in the coating increased，and the element concentration gradient became gentle gradually.From the property of coating，the hardness of coating increased first and then decreased.Moreover， the friction coefficient increased first and then decreased， and the curve fluctuation of friction coefficient increased.The end wear of the scratch decreased obviously at first and then increased slightly，and the bottom undulation of the furrow touched by the pointer gradually increased.

Surface treatment can effectively enhance the corrosion resistance of parts， but its improvement degree needs to be determined by specific corrosion test and corresponding evaluation methods， and the corrosion method and test results should have good reproducibility.In view of the long time to carry out corrosion evaluation in the environment close to the actual use of parts， it is very important to design reasonable accelerated corrosion test conditions and methods.This paper discussed the environmental corrosion characteristics of surface-treated components and the corresponding corrosion test methods， characteristics and evaluation standards， starting from the evaluation of the characteristics of corrosion test conditions and corrosion characteristics of surface-treated components.Moreover， the characteristics of salt spray， accelerated corrosion test and atmospheric environment corrosion of surface-treated components， such as the placement angle of parts in salt spray test， the thickness of surface water film， the influence of environmental temperature and humidity， and the corrosion rate， were analyzed and discussed， which provided supports for the scientific evaluation of the corrosion resistance of surface-treated components.

With the increasing urgency of hydrogen blending transportation in in-service natural gas pipelines in the development demand of hydrogen energy utilization， in-service pipeline materials will face the safety risk of running in hydrogen environment.To investigate the hydrogen embrittlement properties of in-service natural gas pipelines under hydrogen blending conditions， the slow strain rate tensile test and fatigue crack growth test of pipeline steel in hydrogen environment were carried out on X60 pipeline steel of an in-service natural gas pipeline， the effect of hydrogen on the tensile and fatigue properties of the tube was analyzed.The results indicated that under a total pressure of 6.4 MPa and a hydrogen blending ratio of 5%， the hydrogen embrittlement sensitivity of the in-service X60 pipe was relatively low， with fractures exhibiting mostly ductile fracture characteristics.The 5%hydrogen blending ratio did not affect the fracture characteristics.In the same hydrogen blending environment， however， the fatigue crack growth rate of X60 pipeline steel was influenced by the hydrogen environment and the stress intensity factor range at the crack tip.When the stress intensity factor range exceeded a certain threshold， the fatigue crack growth rate of X60 pipeline steel increased dramatically.The fatigue crack growth mode transitioned from ductile fracture dominated by plastic deformation at the crack tip to a mixed fracture of brittle and ductile fracture under the combined effects of hydrogen and cyclic loading.The hydrogen embrittlement sensitivity and fatigue performance of the X60 bend pipe material will be key evaluation indicators for hydrogen blended natural gas transportation in in-service pipelines.

AC/DC stray current interference corrosion has become one of the main causes of pipeline failure and damage， which seriously threatens the safety of pipeline operation.In order to understand the characteristics of different AC-DC stray current interference sources and their influence on the cathodic protection parameters of pipelines， the coupon method was used to monitor the interference sources of different types in a gas pipeline for a long time.Based on the test results， the typical interference characteristics of 7 types of interference types， including AC and DC static interference， dynamic interference and statically dynamic complex interference， were analyzed and summarized.Meanwhile， for complex AC and DC mixed interference， the corresponding evaluation indexes， threshold ranges， criteria and recommended methods were proposed for personal safety， AC and DC mixed interference and valve chamber insulation facilities.The research results provide a basis for pipeline operators to quickly identify the types of stray current interference sources， formulate corresponding protective measures， and reduce the risk of pipeline corrosion caused by complex stray current interference.

In order to investigate the causes of corrosion-induced perforation failure of 20 steel sewage pipes in a shale gas field，scanning electron microscopy (SEM)， energy dispersive spectroscopy (EDS) and Raman spectroscopy were used to observe the corrosion morphology and characterize the corrosion products of the sewage pipes in a shale gas field.Corrosion simulation tests were conducted based on the actual operating conditions， and the causes of corrosion failure of the 20 steel sewage pipes were systematically analyzed.Results showed that there were sulfate-reducing bacteria (SRB)， saprophytic bacteria (TGB) and other bacteria， and the sewage had a significant scaling tendency.The corrosion products on the sewage pipe surface were mainly Fe2O3， FeCO3， and FeOOH， with Cl and S elements accumulated in the pits under the corrosion layer.As the immersion time in sewage increased， the uniform corrosion rate and the maximum pitting corrosion rate of the 20 steel initially decreased and then increased， with the pitting depth increasing rapidly in the later stage of corrosion.Under-scale corrosion and bacterial corrosion were identified as the main factors contributing to the corrosion failure of the sewage pipes.

The impressed current cathodic protection system primarily faces issues such as core component failures and inadequate system performance.To ensure the normal and stable operation of the cathodic protection system and improve its management efficiency， an analysis and summary of common faults and their causes in the system were conducted.By monitoring the output parameters using a potentiostat， this study provided a reference for the subsequent automatic fault diagnosis and on-site rapid troubleshooting of the cathodic protection system.