Justus Tercius, Gonçalves Priscila, Seifert Martin, Leite Mateus L, Probst Sônia M H, Binder Cristiano, Motz Günter, Klein Aloisio N
Materials Laboratory (LabMat), Mechanical Engineering Department, Federal University of Santa Catarina, Florianópolis BR-88040-900, Brazil.
Ceramic Materials Engineering (CME), University of Bayreuth, D-95440 Bayreuth, Germany.
Materials (Basel). 2019 Mar 19;12(6):914. doi: 10.3390/ma12060914.
Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse engineering applications. However, their inherent porosity increases the susceptibility to oxidation and sealing their surface is mandatory to avoid premature degradation. Alongside, polymer derived ceramics (PDCs), such as silicon-carbonitride, have drawn attention concerning their high temperature and chemical stability. However, PDCs undergo volume shrinkage during ceramization that leads to defect formation. The shrinkage can be compensated by the addition of fillers, which are also capable of tailoring the ceramic resulting properties. This work evaluates the processing of PDC-based coatings loaded with ZrO₂ and glass fillers to compensate for the shrinkage, densify the coating and seal the sintered steel surface. Therefore, polymeric slurries were sprayed onto sintered steel substrates, which were pyrolyzed at different temperatures for microstructural and oxidation resistance evaluation. Microstructural modifications caused by the enhanced glass viscous flow during pyrolysis at 800 °C resulted in more homogeneous, dense and protective coatings, which reduced the mass gain up to 40 wt% after 100 h of oxidation at 450 °C in air in comparison to the uncoated substrate. Moreover, no macrocracks or spallation were detected, confirming the feasibility of PDC composite barrier coatings for sintered steels.
粉末冶金是一种具有竞争力的技术，可用于生产各种工程应用中的黑色金属近净形零件。然而，其固有的孔隙率增加了氧化的敏感性，因此必须对其表面进行密封，以避免过早降解。此外，聚合物衍生陶瓷（PDC），如碳氮化硅，因其高温和化学稳定性而受到关注。然而，PDC在陶瓷化过程中会发生体积收缩，从而导致缺陷形成。添加填料可以补偿收缩，填料还能够调整陶瓷的最终性能。这项工作评估了负载ZrO₂和玻璃填料的基于PDC的涂层的加工过程，以补偿收缩、致密化涂层并密封烧结钢表面。因此，将聚合物浆料喷涂到烧结钢基材上，在不同温度下进行热解，以评估微观结构和抗氧化性能。800℃热解过程中玻璃粘性流动增强导致的微观结构变化产生了更均匀、致密和保护性更好的涂层，与未涂层的基材相比，在450℃空气中氧化100小时后，质量增益降低了40 wt%。此外，未检测到宏观裂纹或剥落，证实了PDC复合阻挡涂层用于烧结钢的可行性。
