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To investigate the corrosion damage and degradation mechanism of NiCoCrAlY/AlSiY composite coatings in alternating high and low temperature marine environments, the corrosion damage behavior of NiCoCrAlY/AlSiY composite coatings was studied by designing the alternating high and low temperature oxidation and high temperature oxidation-acidic salt spray alternating tests. Results showed that after 50 cycles of alternating high and low temperature oxidation at 750 ℃, the coating underwent oxidative erosion in the oxidation test, but the integrity of the surface structure was not damaged. After the experiment, the weight of the alloy increased by only 3.87 mg/cm2, indicating that the coating effectively inhibited the diffusion of oxygen into the interior and prevented the substrate from oxidative attack. During the 50 cycles of alternating high temperature oxidation and acidic salt spray tests, the NiCoCrAlY/AlSiY composite coating experienced severe corrosion degradation, and the alloy weight increased to as high as 13.52 mg/cm2 by the end of the test. Due to long-term salt spray erosion, the oxide layer structure weakened, leading to surface loosening, the formation of corrosion pits, and even peeling. As the number of alternating cycles of high temperature oxidation-acidic salt spray increased, the critical reaction causing coating damage shifted from oxidative erosion to thermal corrosion. The chlorine, generated from the eutectic reaction of the mixed salt, acted as a catalytic carrier and accelerated the growth of oxidation products, demonstrating that the NiCoCrAlY/AlSiY composite coatings had weak corrosion resistance under alternating high temperature oxidation-acidic salt spray environments.

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Background: To investigate pathologically the characteristics of proximal bronchial invasion of lung cancer, and to provide the theoretic basis for the selection of a proper operation mode., Methods: A total of 398 patients with lung carcinoma underwent radical pulmonectomy and systematic lymphadenectomy. The proximal bronchi and the hilar and mediastinal lymph nodes of their operatively resected specimens were selected for pathological study., Results: (1)The direct invasion of cancerous cells through mucous, submucous or multiple layers was the most frequent way during lung cancer spread, rating 9.3%, 21.8% and 68.9% respectively. 96.4% of the cancerous invasion occurred at the proximal bronchial wall less than 1.5 cm apart from the cancer margin. The extension of invasion correlated with the histopathologic type of cancer, mode of invasion and TNM classification. (2)The cancer infiltration by the nodes metastasizing into the bronchus wall (bronchial external tunica or cartilage) was also an important way for the cancer to spread, especially in adenocarcinoma. The poor differentiated adenocarcinoma has significantly higher metastatic rate and infiltration rate than the well differentiated ( P < 0.01, P < 0.01). There were 22 such cases, including 3 of lobar bronchus wall invaded by N1 metastasis and 19 of main bronchus wall by N2 metastasis., Conclusions: For radical removal of tumor, the key point for selecting a rational operation mode is to keep a distance of 1.5 cm or more between the excision margin of the bronchus and the tumor, to pay attention to the bronchial wall invasion caused by the metastatic lymph nodes, even in peripheral adenocarcinoma, and to dissect extensively and completely the lymph nodes of the hilar and upper and lower mediastinum at the homolateral thoracic cavity.