Role of surface finishing on pitting corrosion of a duplex stainless steel in seawater

Localized corrosion of duplex UNS S32550 stainless steel in seawater was investigated in the laboratory and in field trials for several surface finish conditions: polished, ground, and sandblasted. Electrochemical data obtained by polarization curves showed that the smoother, polished surface had better characteristics (higher pitting and protection potentials) than the ground or sandblasted surfaces. However, despite its high degree of roughness, the sandblasted surface was the most resistant in field conditions, exhibiting the lowest number of sites attacked. Internal compressive stresses created by sandblasting seem also to have an “unsensitizing” effect on sensitized zones that exist in cast steel (due to repairs of mold defects), reducing its susceptibility to microbiologically influenced corrosion (MIC). Such stresses are not generated in polished or ground surfaces, and localized MIC attack can occur.     

表面改性金属材料双极板前处理的研究

在不锈钢表面制备一层导电性好、耐腐蚀的薄膜,是获得高性能质子交换膜燃料电池双极板材料的有效方法.实验分别采用抛光、喷砂和拉砂三种方法对不锈钢基体进行了前处理,然后利用物理气相沉积技术在不锈钢表面制备了TiN膜.观察了双极板材料的微观结构.并对其导电性和耐蚀性进行评价,以研究基体前处理对性能的影响.经过不同的前处理,双极板材料表面呈现出完全不同的微观结构.双极板材料的界面导电性与有效接触面积密切相关.当与碳纸接触时,抛光前处理的双极板材料导电性最好;当与膨胀石墨接触时,喷砂前处理的双极板材料电阻最低.在模拟电池腐蚀环境下0.5 mol/L H2SO4 2×10-6 F-的电化学腐蚀结果显示,喷砂前处理的双极板材料具有最好的耐腐蚀能力.     

DZ125定向凝固合金的再结晶行为研究

研究了DZ125定向凝固合金发生再结晶的温度条件以及吹砂条件对其再结晶行为的影响。结果表明：铸态和热处理态DZ125定向凝固合金开始发生再结晶的温度基本相同,均在1000—1050℃范围内;该合金的再结晶深度随热处理温度的升高而增大,当热处理温度低于1150℃时,增大的幅度较小,当温度超过1150℃后,再结晶深度迅速增大,γ相的溶解是DZ125合金再结晶的控制因素;随着吹砂压力或吹砂时间的增加,DZ125合金表面变形量增大,再结晶深度也随之增大。     

喷砂与喷涂模型及模拟装置研究

开发了用于教学培训、技能考核和模拟试验的喷砂与喷涂的专利模型和装置。介绍了它们的构成,制作过程和使用方法。     

Effects of surface treatments on the bond strength of composite resin to hybrid computer-assisted design/manufacturing blocks

The aim of this study was to evaluate the repair bond strength of a dimethacrylate-based composite to two hybrid CAD/CAM blocks after different surface treatments. One hunded and twenty specimens were prepared from two different CAD/CAM blocks (Lava Ultimate (L), Cerasmart (C)). After thermal aging, specimens from each group (n?=?60) were divided into 6 treatment groups (n?=?10): (1) No treatment (2) Phophoric acid (37%) for 60?s, (3) Hydrofluoric acid (8%) for 60?s, (4) Sanblasting with 50-µm aluminium oxide (5) Er,Cr:YSGG laser treatment at 2?W and (6) Er,Cr:YSGG laser treatment at 3?W. Single Bond Universal was applied on all specimens and a dimethacrylate-based composite (Tetric N-Ceram) was bonded using Teflon tubes. After thermal cycling, shear bond strength (SBS) was tested, and failure modes were evaluated. Two-way ANOVA and independent t-test were used for statistical analysis (p?<?0.05). The highest SBS values were detected at Er,Cr:YSGG laser treatment groups (3W) (L:22.7?MPa, C:22.6?MPa). Lowest SBS values were obtained at no surface pretreatment groups followed by phophoric acid treatment groups which were significantly lower than sandblasting, hydrofluoric acid treatment and Er,Cr:YSGG laser treatment groups (p?=?0.001). The universal adhesive Single Bond Universal had no effect on promoting bond strength to hybrid ceramics alone or with phosphoric acid. Sandblasting, hydrofluoric acid and laser treatment were effective at increasing repair bond strength, for both Lava Ultimate and Cerasmart.     

喷砂对6082铝合金焊接接头残余应力的影响

采用喷砂对铝合金车体用6082铝合金进行了表面处理。采用X射线衍射法测试并对比分析对接、搭接和十字焊接接头喷砂处理前后的残余应力。结果表明,喷砂处理前,对接、搭接和十字焊接接头的纵向残余应力均呈双峰状分布,最大残余应力出现在焊趾附近区域,而横向残余应力呈多峰状分布;喷砂处理后,其纵向和横向应力均呈现为压应力状态,并且应力跨度显著减小,应力分布更均匀。残余压应力的存在可以有效抑制表面裂纹的萌生,提高其疲劳强度和延长使用寿命。     

油管喷砂生产线除尘系统设计

油管表面喷砂处理大多采用的是喷料为普通硅砂的开放式喷砂设备,存在严重的环境污染问题。为实现油管内、外表面的自动化喷砂处理,改善工作环境,使粉尘排放达标,提出了由重力沉降室、旋风除尘器、袋式除尘器组成的3级除尘系统,并完成了适用于油管内、外表面喷砂的2套除尘系统的设计和关键设备的优选。     

Fabrication of modeling platform for fused deposition modeling using vacuum casting

This study presents a cost‐effective approach for rapid fabricating modeling platforms utilized in fused deposition modeling three‐dimensional printing system. A small‐batch production of modeling platforms about 20 pieces can be obtained economically through silicone rubber mold using vacuum casting without applying the plastic injection molding. The air venting systems is crucial for fabricating modeling platform using vacuum casting. Modeling platforms fabricated can be used for building rapid prototyping model after sandblasting. This study offers industrial value because it has both time‐effectiveness and cost‐effectiveness.