Surface & Coatings Technology最新文献

{"title":"Superior oxidation and erosion resistant nanolayered multilayered Cr/Cr2N coating on Ti6Al4V for high-temperature applications","authors":"Venkataramana Bonu ,&nbsp;Sai Kumar K. ,&nbsp;Sudharsan G. ,&nbsp;Praveen Kumar V. ,&nbsp;Harish C. Barshilia","doi":"10.1016/j.surfcoat.2026.133249","DOIUrl":"10.1016/j.surfcoat.2026.133249","url":null,"abstract":"<div><div>Solid particle erosion and oxidation-assisted erosion at temperatures above 400 °C severely affect Ti6Al4V components such as gas turbine compressor blades. To address this issue, an erosion- and oxidation-resistant Cr/Cr₂N multilayer coating with gradient interfaces (thickness ~ 11 μm, bi-layer period ~8 nm) was developed on Ti6Al4V. The phase of the as-deposited coating by magnetron sputtering was Cr/CrN; further annealing of this coating at 400 °C resulted in Cr/Cr₂N. Initially, individual Cr, CrN, and Cr/CrN films (thickness ~ 1.5 μm) were deposited to study crystallographic properties. The as-deposited multilayer film exhibited a broad XRD peak related to Cr/CrN phase. However, after annealing at 400 °C, the film phase transformed into a well-crystallized Cr/Cr₂N structure. The erosion resistance of the ~11 μm thick coating was studied from room temperature to 800 °C following ASTM-G76 standard. The average erosion resistance of the coated Ti6Al4V (at different impinging angles) was ~76 times higher than that of bare Ti6Al4V at 400 °C @ 30 m/s erodent speed. In addition, the coated Ti6Al4V exhibited superior erosion resistance up to 800 °C, compared to bare Ti6Al4V. Bare Ti6Al4V exhibited oxidation-induced brittle cracking at temperatures ≥600 °C, whereas the coating did not show any cracks. Oxidation tests at 800 °C for 30 min revealed severe material loss (~11 μm) for bare Ti6Al4V, while a thin, stable Cr₂O₃ layer (~1 μm) formed on Cr/Cr₂N coating, confirming its excellent high-temperature oxidation and erosion resistance performance at higher temperatures. Additionally, the high-temperature erosion mechanism for both coated and uncoated Ti6Al4V is also explained.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133249"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal cycling failure mechanism and damage quantification of PS-PVD sprayed Yb2Si2O7 environmental barrier coating","authors":"Rong Ma ,&nbsp;Tingchen Du ,&nbsp;Xueling Fan ,&nbsp;Xiaolong Gao ,&nbsp;Jiachen Qian ,&nbsp;Weihai Li","doi":"10.1016/j.surfcoat.2026.133240","DOIUrl":"10.1016/j.surfcoat.2026.133240","url":null,"abstract":"<div><div>The thermal cycling behavior and failure mechanism of Yb₂Si₂O₇ environmental barrier coatings (EBCs) deposited by plasma spray-physical vapor deposition were investigated after 1000 cycles of exposure in dry air at 1350 °C and 1250 °C. A damage quantification method based on interfacial damage was developed to characterize the degradation of EBCs. The results revealed that thermal cycling induced the formation of pores in the top coat (TC) and bond coat (BC) layers as well as in the interface regions. The thermally grown oxide (TGO) layer at the interface progressively thickened, leading to the initiation of vertical cracks, followed by delamination at the TGO/BC interface. The damage caused by thermal cycling was significantly more severe than that induced by isothermal oxidation, with localized delamination observed after only 800 cycles. Interfacial delamination was the primary mode of thermal cycling damage. Frequent temperature fluctuations resulted in oxidation instability, manifested by the formation of TGO layers with distinct color contrasts. Furthermore, a damage constitutive model was established based on the degradation of critical spallation resistance and thermoelastic theory. The damage quantification theory was validated, as evidenced by the prediction of damage evolution and the corresponding delamination failure in room-temperature compression tests after thermal cycling. The damage evolution followed a power-law function of the number of cycles, providing a valuable reference for the quantitative assessment of EBCs damage.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133240"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tailoring B2 phase precipitation via LDED and annealing to enhance tribological properties of low-density steel coatings","authors":"Fengqin Ji ,&nbsp;Songyang Zhang ,&nbsp;Ming Pang ,&nbsp;Chengning Li","doi":"10.1016/j.surfcoat.2026.133252","DOIUrl":"10.1016/j.surfcoat.2026.133252","url":null,"abstract":"<div><div>To integrate lightweight design with wear resistance, Fe-Mn-Al-C low-density steel coatings were fabricated via laser directed energy deposition (LDED). Unlike conventional methods involving cold rolling and annealing to precipitate B2 phases, this study employed a novel approach whereby polygonal B2 phases were precipitated by controlling the laser power, followed by a post-annealing treatment at 900 °C for 15 min to form needle-type B2 phases. This strategy incorporated two distinct B2 phase morphologies into the coating, and their effects on wear property were systematically investigated. The results indicate that during the deposition process, polygonal B2 phases preferentially nucleated and progressively covered the ferrite matrix. As laser power increased from 1200 W to 1600 W, the content of polygonal B2 phases increased progressively, accompanied by a rise in BCC phase fraction from ∼19.2% to 26.0%. Concurrently, the size and content of κ-carbides and D0₃ phases also increased, leading to enhanced wear resistance. After annealing, submicron-scale needle-type B2 phases precipitated in the austenite. Together with the polygonal B2 phase containing nanoscale D0₃ phase, they formed a reinforcing skeleton, reducing the wear rates at room temperature and 550 °C to 7.647 × 10⁻⁵ mm³N⁻¹ m⁻¹ and 0.304 × 10⁻⁵ mm³N⁻¹ m⁻¹, respectively. The annealing process also promoted the dissolution of κ-carbides and a reduction in size of D0₃ phases. The superior wear resistance is attributed to a multiscale synergistic mechanism involving the strengthening effect of the dual-morphology B2 phases and the protective role of the oxide layer. This study provides a novel pathway for designing lightweight wear-resistant coatings for high-temperature applications.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133252"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dual strengthening mechanism of mechanical properties and oxidation resistance in NiCoCrAlY coatings by nano-oxide dispersion strengthening","authors":"Honglin Mou ,&nbsp;Guozheng Ma ,&nbsp;Zhihai Cai ,&nbsp;Xianyong Zhu ,&nbsp;Haichao Zhao ,&nbsp;Ming Liu ,&nbsp;Guangdong Gong ,&nbsp;Haocheng Wen ,&nbsp;Bing Wang ,&nbsp;Haidou Wang","doi":"10.1016/j.surfcoat.2026.133277","DOIUrl":"10.1016/j.surfcoat.2026.133277","url":null,"abstract":"<div><div>To enhance the mechanical properties and thermal shock resistance of thermal barrier coating (TBC) bond coats, this study modified conventional NiCoCrAlY by incorporating uniformly dispersed 1.0 wt% CeO₂ and 0.5 wt% Al₂O₃ nanoparticles to achieve oxide dispersion strengthening (ODS). Systematic microstructural characterization, mechanical testing, water-quenching thermal shock cycling, and transmission electron microscopy (TEM) analyses were conducted to investigate the effects of ODS on the mechanical properties and thermally grown oxide (TGO) growth of the coatings under extreme thermal shock conditions. The results indicate that ODS-induced grain refinement reduced the coating grain size by 19.0%, increased microhardness by 6.4%, enhanced elastic recovery by 10.4%, and improved adhesion strength by 21.4%. The ODS-NiCoCrAlY coating formed a thinner, denser TGO layer primarily composed of stable α-Al₂O₃ and NiAl₂O₄, with minor fine-grained NiO. This behavior is attributed to nanoparticle-induced grain refinement (which facilitates Al diffusion) and rare-earth oxide segregation at grain boundaries (which suppresses Ni diffusion and inhibits the formation of volatile CrO₃). In contrast, the conventional NiCoCrAlY coating exhibited a thicker, more porous TGO layer containing coarse NiO, γ-Al₂O₃, and voids. This study elucidates the microscale interactions between ODS and TGO, confirming that synergistic performance enhancement can be achieved through grain refinement, rare-earth oxide grain boundary segregation, and optimized high-temperature oxidation. The findings provide valuable theoretical and experimental guidance for the design of high-performance TBC bond coats.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133277"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oxidation and molten salt corrosion behavior of AlCoCrFeNi2.1Mo0.3 high-entropy coating manufactured by atmospheric plasma spraying","authors":"Junjie Peng ,&nbsp;Baiyue An ,&nbsp;Liang Ning ,&nbsp;LiLi Zheng ,&nbsp;Hongxin Zhang ,&nbsp;Zhiyong Wang ,&nbsp;Hui Jiang ,&nbsp;Junru Li","doi":"10.1016/j.surfcoat.2026.133268","DOIUrl":"10.1016/j.surfcoat.2026.133268","url":null,"abstract":"<div><div>For salt-containing high-temperature service conditions, we sought to clarify the corrosion-resistance mechanism of the AlCoCrFeNi_2.1 system after a small Mo addition and to assess its suitability as a bond coat. An AlCoCrFeNi_2.1Mo_0.3 surface coating was deposited by atmospheric plasma spraying. Isothermal oxidation and NaCl molten-salt corrosion tests were performed at 350–600 °C, mass changes were recorded, and phase and morphology analyses of the surface and cross-section were conducted using XRD and SEM/EDS to infer the underlying mechanisms. The coating exhibits an FCC matrix with a Mo-containing lamellar–splat microstructure, and the interface shows good adhesion. After exposure, the dominant products are Al₂O₃, Cr₂O₃, MoO₂, MoO₃, and the spinel (Ni,Co)(Cr,Fe)₂O₄. Cross sections reveal no continuous external oxide scale, and internal selective oxidation is predominant. Continued Al depletion suppresses the development of a continuous Al₂O₃ scale, and the surface instead forms spinel. Mo enriches at the surface as MoO₃ clusters, which diminish at elevated temperatures due to volatilization and reduction. Based on this observation, we propose an evolution model of “oxygen partial pressure gradient–driven MoO₂ and MoO₃ transformation,” which explains how the NaCl-induced chlorination–reoxidation cycle accelerates internal oxidation and prevents the formation of a continuous Al₂O₃ scale. This study provides mechanistic evidence to guide the compositional and process optimization of high-entropy alloy coatings.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133268"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of WC content on cracking susceptibility of laser cladding Ni60A + WC layers by a new testing method","authors":"Kun Liu ,&nbsp;Yibin Wu ,&nbsp;Zengcao Gao ,&nbsp;Yuxuan Ren ,&nbsp;Jie Li","doi":"10.1016/j.surfcoat.2026.133266","DOIUrl":"10.1016/j.surfcoat.2026.133266","url":null,"abstract":"<div><div>In this paper, the effect of WC content on the cracking susceptibility of Ni60A + WC layers on Inconel 718 superalloys was evaluated. A new method is proposed to assess the cracking susceptibility through comparing the cracking rate. This new method is widely applicable, simple to prepare, and low in cost, which exhibits significant potential for engineering application. Focusing on the new cracking susceptibility testing method, model prediction and analysis on the dilution rate were investigated. Stress analysis was performed and the stress-induced causes for the cracking of the clad layer were identified. The influence of different WC contents on the dilution rate and the properties of clad layer was analyzed. The results show that as the WC particle content increases, the dilution rate decreases significantly, but the crack rate keeps rising. When the WC content increases from 15% to 35%, the crack rate rises from 17.2% to 25.6%, the average hardness of the clad layer increases from 469.1 HV_0.5 to 550.2 HV_0.5, and the corrosion resistance decreases.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133266"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Defect-modulated nanolayered TiN/AlSiN coating with exceptional durability against marine corrosion","authors":"Mao Li ,&nbsp;Zhiqi Feng ,&nbsp;Zhonghao Liu ,&nbsp;Qiance Q.I. Zhang ,&nbsp;Egemen Avcu ,&nbsp;Bin Zhu ,&nbsp;Xuanpu Dong ,&nbsp;Jeff Th.M. De Hosson ,&nbsp;Huatang Cao","doi":"10.1016/j.surfcoat.2026.133255","DOIUrl":"10.1016/j.surfcoat.2026.133255","url":null,"abstract":"<div><div>Corrosion of components exposed to marine environment results in significant economic losses, underscoring the urgent need for development of durable coatings to resist chloride-induced degradation. In this work, a ∼ 3 μm-thick nanolayered TiN/AlSiN coating was deposited on Ti-6Al-4 V alloy by cathodic arc ion plating through alternating TiN and AlSiN layers, and its performance was systematically compared with single-layer TiN and AlSiN coatings and the corrosion protection and failure mechanisms in marine environments are elucidated. Results show that the multilayer architecture transforms detrimental three-dimensional (3D) droplet defects in AlSiN into less harmful two-dimensional (2D) interlayer defects, thereby mitigates their role in corrosion initiation. Electrochemical testing demonstrates that the multilayer achieves the highest corrosion potential (−0.33 V) and reduces corrosion current density by ∼93% relative to TiN, evidencing superior chloride resistance in seawater. Long-term salt spray testing (960 h) further confirms sustained protection in a marine atmosphere, where a unique three-layered degradation structure retards coating failure. These findings establish a new paradigm in defect modulation, suggesting that multilayer design not only enhances mechanical robustness but also reconfigures unavoidable deposition defects into controllable lateral forms, thereby extending service durability under marine atmospheric exposure.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133255"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanisms of deposit formation in injection moulding cavities and the role of tool coatings and internal release agents","authors":"Kai Lingnau ,&nbsp;Chantal Theile-Rasche ,&nbsp;Klaus Vissing ,&nbsp;Elmar Moritzer ,&nbsp;Guido Grundmeier ,&nbsp;Martin Wiesing","doi":"10.1016/j.surfcoat.2026.133280","DOIUrl":"10.1016/j.surfcoat.2026.133280","url":null,"abstract":"<div><div>A major challenge in the injection moulding industry is the formation of tool build-up and the formation of deposits. Current solutions include the use of hard coatings paired with low surface energy finishes, e.g. sol-gel coats or PTFE-based polishes, so that there is a need for more durable, scratch-resistant and PTFE-free coating solutions. Aside this technological deficit, there is also a deep lack of knowledge about the functioning principles of tool coatings and their influence on the formation of deposits.</div><div>We therefore introduced low surface energy coatings deposited by plasma-enhanced physical vapour deposition (PE-CVD), which enable to tailor hardness, Young's modulus and surface energy in a wide range.</div><div>The interactions between such coatings and molten polycarbonate (PC) were analysed to test their stability against the harsh conditions of injection moulding and to reveal the fundamental mechanisms of deposit formation. We found that interfacial chemical reactions cause deposit formation in the case of the bare steel, which were avoided by the PE-CVD coatings in presence of the internal release agents in Makrolon 2405.The PE-CVD coatings therefore shifted the interactions into a regime where deposits were formed by wetting instead.</div><div>The synergism of internal release agents and PE-CVD coatings was studied in a model system consisting of polycarbonate and pentaerythritol tetrastearate (PETS) with varying degree of esterification (hydroxyl value). The results disclosed that the role of the release agent is limited to interact predominantly with the polymer surface and to decrease its surface energy in presence of the PE-CVD coating, because of the lower surface energy of the latter.</div><div>However, the formation of a low-molecular weight weak boundary layer could not be prevented by the PE-CVD coating. This motivated to discuss the thermodynamical foundations of the observed wetting of the deposits using basic wetting theory. It was highlighted that matching the surface energy of a coating to the base polymer in a compound removes uncompensated interfacial energies so that deposits stay formally dispersed. This notion correlated with the observed reduction of deposits by the PE-CVD coatings and internal release agents and provides therefore an explanation of their functioning. Finally, we discussed the concept that an ideal surface technological solution shall decrease the interfacial energies to avoid deposits but may also decrease the individual surface energies to lower adhesion.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133280"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimizing hBN-PHB composites to enhance high-speed tribological performance of CoCrAlY abradable seal coatings for Ti2AlNb compressor","authors":"Rui He ,&nbsp;Shuai Yang ,&nbsp;Ning Li ,&nbsp;Yanhao Che ,&nbsp;Peixuan Geng ,&nbsp;Zizhuo Liu ,&nbsp;Jiqiang Wang ,&nbsp;Tianying Xiong ,&nbsp;Xinyu Cui","doi":"10.1016/j.surfcoat.2026.133229","DOIUrl":"10.1016/j.surfcoat.2026.133229","url":null,"abstract":"<div><div>To address the challenge of sealing clearance control in high-performance aero-engine compressors, this study developed a novel CoCrAlY-hBN-PHB abradable seal coating system for Ti₂AlNb components operating at ~650 °C. The work systematically investigated the effects of hBN (5–15 wt%) and PHB (2–10 wt%) content on the microstructure and high-speed tribological performance of coatings. The results demonstrate that coating hardness could be effectively tailored through composition design, but excessive hBN (&gt;10 wt%) reduced deposition efficiency and induced anomalous hardening in the 15hBN + 10PHB coating due to in-situ compaction effects. Coating hardness was inversely correlated with abradability. Although the softest 10hBN + 10PHB coating exhibited optimal abradability, its excessively high interconnected porosity could compromise structural integrity and corrosion resistance. Tribological analysis revealed that the superior temperature rise rate of the blade tip caused preferential heat accumulation, generating localized temperatures exceeding 1072 °C that triggered B2 phase transformation and material transfer to the coating via microwelding. Concurrently, work hardening of the coating surface further degraded abradability and increased blade wear. The 15hBN + 6PHB composition was identified as the most balanced formulation, though further improvements by architectural grading, hBN/PHB distribution optimization, and blade tip thermal protection are necessary for practical application. This work elucidates the critical thermo-mechanical coupling mechanisms governing Ti₂AlNb/coating interactions and provides essential insights for designing next-generation abradable seal coating system.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133229"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146192263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Uniform alumina coatings on the inner surfaces of aluminum alloy tubes by plasma electrolytic oxidation for enhanced mechanical and corrosion resistance","authors":"Yee Ng,&nbsp;Xian Yi Tan,&nbsp;Tzee Luai Meng,&nbsp;Anna Marie Yong,&nbsp;Hongfei Liu","doi":"10.1016/j.surfcoat.2026.133289","DOIUrl":"10.1016/j.surfcoat.2026.133289","url":null,"abstract":"<div><div>Protective coatings on the inner surfaces of metallic tubes are critical for aerospace, automotive, marine, and energy applications, yet remain a significant challenge due to difficult access. Here, we demonstrate the successful fabrication of dense, uniform alumina coatings on the inner walls of Al-6061 alloy tubes (20 mm diameter, 200 mm length) using plasma electrolytic oxidation (PEO). The conformal coatings (∼10 μm) exhibit predominantly γ-Al₂O₃ phase with minor α-Al₂O₃ inclusions, confirmed by X-ray diffraction. Cross-sectional nanoindentation revealed a hardness of ∼8.0 GPa, five times higher than the substrate. Dielectric breakdown strength exceeded 60 kV/mm. Electrochemical testing in 3.5 wt% NaCl showed a reduction in the corrosion current from 0.77 to 0.04 μA and nearly doubled pitting potential induced by the PEO coating. Microstructural investigations further revealed that while uncoated tubes suffered from pitting corrosion, intergranular corrosion, and stress corrosion cracking, the PEO coatings suppressed these degradation modes by mitigating electrolyte penetration and alleviating residual stress. These findings establish PEO as a viable strategy for producing robust inner-surface ceramic coatings, enabling improved reliability of tubular aluminum components in demanding environments.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"524 ","pages":"Article 133289"},"PeriodicalIF":6.1,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146191804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}