Authors: Pisit Apichayakul, Sittichai Wirojanupatump, Sukanda Jiansirisomboon
Abstract: Correlations between in-flight particle, splat and coating microstructure of thermally
sprayed Ni20Cr were investigated. Flame spray and arc spray systems were employed for spraying
Ni20Cr powder and Ni20Cr wire, respectively. The results showed that the arc spray process
produced a broader size distribution for both in-flight particles and splats compared to flame
process. Flower-like splat morphology was obtained from the arc spray whereas a pancake-like
splat was obtained by flame spray. Ni20Cr coating sprayed by arc process had a denser
microstructure, lower porosity and better adhesion at the interface. This could be due to the higher
temperature and velocity from the arc spray process enhancing the melting and adhering for coating
formation.
409
Authors: Shu Hua Li, Fu Chi Wang
Abstract: The ceramic coating was formed by micro-plasma arc oxidation (MPAO) on AZ91D
magnesium alloy. The surface and section morphology of coatings were observed using scanning electron
microscopy. The phase composition of coatings was analyzed by X-ray diffraction. The method of salt fog
experimental was carried out to proof-test performances of anti-corrosion of material. The results showed
that the ceramic coating was composed by loose layer and compact layer. The coating surface has a large
number of grains with various sizes. In addition, there is also a lot of pore in the loose layer, but the
compact layer is tighter than the loose layer. Compact layer has a good combination with substrate
magnesium alloy. The MPAO coating is mainly composed of silica oxide (MgAl2Si3O12 and β-Mg2SiO4
and (Mg4Al14) (Al4Si2)O20) and composite oxide of Mg and Al (δ-MgAl28O4). The performance of
resistant corrosion of AZ91D coved by ceramic coating is higher than AZ91D magnesium alloy. The
corrosion ratio of AZ91D alloy coved by ceramic coatings to AZ91D alloy is 1:8.61.
2451
Authors: Wei Gao, Zhen Yun Zhao
Abstract: Pseuado Zn-Al alloy coatings were made by using of dissimilar metal wire arc spraying technology on the surface of the steel Q235 and the H2S corrosion experiment was carried out on the coatings. The corrosion rate was calculated with weight-loss method. The configurations of Zn-Al coatings before and later suffered corrosion were observed with scanning electron microscope, and the coating surfaces were analyzed with energy spectrum. The corrosion potential of the coatings was tested by using the electrochemistry testing system. The corrosion results showed that Zn-Al coatings can protect the covered steel surface and the steel substrate exposing in the corrosion environment. Being processed with pore sealer, the coatings have shown more excellent corrosion resistance.
563
Authors: Ze Min Chen, Pin Lu, Qiu Hong Dong
Abstract: This study selected sodium silicate, sodium fluoride, glycerol hydroxyl acid, potassium hydroxide and phosphine oxide (LAP) as the stabilizer electrolyte, and then on micro-arc oxidation of magnesium with constant current density. The microstructure, corrosion resistance, chemical composition, structure and characterization of micro-arc oxidation film were determined by SEM and anodic oxidation methods. Experimental results indicated that the test pieces of magnesium would formed an silver-gray uniform densification oxide film on the surface by micro-arc oxidation treatment, and the corrosion resistance of magnesium film-formed had increased by potentiodynamic polarization curve testing.
595
Authors: Ya Ping Zhang, Xiang Dong Liu, Jing Zhang
Abstract: Using micro-arc oxidation technology in preparation Ti6Al4V alloy surface oxidation film, adding to the electrolyte H2O2, influence of H2O2 addition amount of oxidation film characteristics has been studied. The results show that, H2O2 addition amount of 4.0 g·L-1, positive critical arcs voltage minimum, for 338 V. SEM analysis showed that, electrolyte of H2O2 addition amount by 1.0 g·L-1 increased to 4.0 g·L-1, film hole diameter after decreasing, micro-arc oxidation film layer of density increases. Oxidation film surface roughness reduced to 7.619 when H2O2 addition amount for 4 g·L-1. With H2O2 addition amount from 1.0 g·L-1 increased to 4.0 g·L-1, micro-arc oxidation film in the wear process mass loss is reduced, wear resistance for promotion.
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