{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T05:02:28Z","timestamp":1789621348489,"version":"build-2803163510"},"reference-count":40,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T00:00:00Z","timestamp":1789430400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100011787","name":"the Natural Science Foundation of Heilongjiang Province","doi-asserted-by":"publisher","award":["PL2024E021"],"award-info":[{"award-number":["PL2024E021"]}],"id":[{"id":"10.13039\/501100011787","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"the National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["52272146"],"award-info":[{"award-number":["52272146"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"award":["52272146"],"award-info":[{"award-number":["52272146"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Laser-directed energy deposition (L-DED) is a key technology for fabricating wear-resistant Stellite-6 coatings on power-plant components. This study aims to clarify the surface cracking mechanism of L-DED Stellite-6 coatings deposited on 22Cr15Ni3.5CuNbN (SP2215) boiler tubes during long-term high-temperature service. The coatings were exposed at 650 \u00b0C for up to 5000 h, and their microstructural evolution and mechanical degradation were systematically characterized using SEM\/EDS, TEM, EBSD, microhardness testing, and impact testing. High-temperature service induces the decomposition of M23C6 precipitates at dendrite boundaries, releasing Cr, C, and W atoms that subsequently migrate toward the coating surface. Owing to the rapid interstitial diffusion of C, a carbon-enriched surface region preferentially develops, accompanied by progressively increasing coverage of surface Cr2O3 and subsurface M23C6. Consequently, the surface hardness increases from 441.6 HV0.1 at 0 h to 613.1 HV0.1 after 5000 h, whereas the impact-absorbed energy decreases from 82.8 \u00b1 4.2 J to 5.9 \u00b1 2.5 J. An increase of 1 HV0.1 in hardness corresponds to an approximately 0.448 J reduction in impact-absorbed energy. Mechanistically, local stress concentration associated with Cr2O3 formation, interfacial sliding promoted by lattice mismatch, and crack nuclei originating from pores between chain-like M23C6 precipitates collectively promote crack initiation and propagation. These results demonstrate that precipitate decomposition, elemental redistribution, and subsequent oxide\/carbide evolution govern the progressive surface embrittlement and cracking of L-DED Stellite-6 coatings during long-term high-temperature service. This study provides mechanistic insight into the coupling between microstructural evolution and surface failure and offers a theoretical basis for microstructural regulation and long-term reliability assessment of wear-resistant Co-based coatings used in power-plant components.<\/jats:p>","DOI":"10.3390\/ma19183911","type":"journal-article","created":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T08:16:48Z","timestamp":1789460208000},"page":"3911","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Surface Cracking Mechanism of SP2215\/Stellite-6 Components Fabricated by Laser-Directed Energy Deposition During High-Temperature Service"],"prefix":"10.3390","volume":"19","author":[{"given":"Pengcheng","family":"Che","sequence":"first","affiliation":[{"name":"School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150006, China"},{"name":"Harbin Energy Innovation Digital Technology 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Institute of Technology, Harbin 150006, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"given":"Chenglei","family":"Fan","sequence":"additional","affiliation":[{"name":"School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150006, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8128-9456","authenticated-orcid":false,"given":"Yongjiang","family":"Huang","sequence":"additional","affiliation":[{"name":"School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150006, 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