SBIR Phase I: Chemical Vapor Deposition-SiC-Coated Ceramic Bearing Elements of High Damage and Wear Resistance

这个小型企业创新研究第一阶段项目旨在开发替代陶瓷轴承元件，以显著降低成本，提供氮化硅(Si3N4)的性能。采用热等静压(HIPed)或烧结和HIPed Si3N4元素(滚珠或滚子)的混合轴承在机床行业、化工加工行业、真空泵、气相沉积和分子束外延设备、离心机和高速测试设备中显示出优异的性能。尽管表现出色，但世界范围内Si3N4轴承元件的市场规模小得令人沮丧(1995年为-2500万美元)。限制Si3N4元素使用的唯一最重要的因素是成本。本研究项目的前提是，通过化学气相沉积(CVD)沉积并通过设计的残余表面压缩进行增韧的碳化硅轴承表面将具有所需的组织均匀度和表面韧性，以提供与Si3N4相当的滚动接触疲劳和耐磨性，且成本较低。碳化硅轴承元件的成本应低于氮化硅，因为其粉末成本、加工成本和表面精加工成本都较低。与Si3N4相比，由于其优异的耐腐蚀性和抗氧化性，碳化硅元素在恶劣环境中的性能也有望得到改善。第一阶段的具体目标是(1)通过调整无压烧结的碳化硅-碳化钛基材的热膨胀来优化碳化硅涂层中剩余表面压缩的大小，(2)建立最佳的CVD条件以避免有害的涂层亚结构，以及(3)在可与当前轴承等级Si3N4相媲美的RCF试验中展示碳化硅的寿命和耐磨性。第二阶段将解决进一步降低衬底制造成本的问题，并设计在流态化床化学气相沉积反应器中对球体进行碳化硅涂层的经济方法。将开发的CVD-碳化硅涂层滚珠和滚子将用作混合陶瓷轴承的轴承元件。反过来，混合陶瓷轴承将用于机床行业，在机床行业，陶瓷元素的低密度可以降低离心力，在化工加工行业，利用碳化硅元素的耐腐蚀性，以及中温应用。自动化行业中的凸轮从动件是开发CVD-碳化硅涂层轧件的另一个潜在领域。

This Small Business Innovation Research Phase I project aims to develop alternate ceramic bearing elements that can deliver the performance of silicon nitride (Si3N4) at significantly reduced costs. Hybrid bearings incorporating hot-isostatically-pressed (HIPed) or sintered and HIPed Si3N4 elements (balls or rollers) have demonstrated excellent performance in the machine tool industry, the chemical processing industry, in vacuum pumps, vapor deposition and molecular beam epitaxy equipment and centrifuges and high-speed testing equipment. Despite this demonstrated performance the total world-wide market for Si3N4 bearing elements is discouragingly small (- $ 25 million in 1995). The single-most important factor limiting the use of Si3N4 elements is cost. The premise of this research project is that bearing surfaces of SiC deposited by chemical-vapor deposition (CVD), and toughened by designed residual surface compression, will have the required microstructural homogeneity and surface toughness to deliver rolling-contact fatigue and wear resistance comparable to Si3N4 at lower cost. The cost of the SiC bearing elements should be lower than that of Si3N4 because of the lower cost of the powders, processing and surface finishing. SiC elements are also expected to show improved performance in severe environments due to their superior corrosion and oxidation resistance as compared to Si3N4. Specific objectives of Phase I are to (1) optimize the magnitude of the residual surface compression in SiC coatings by tailoring the thermal expansion of pressureless-sintered SiC-TiC substrates, (2) establish optimum CVD conditions to avoid deleterious coating substructures, and (3) demonstrate life and wear resistance of SiC in RCF tests comparable to current bearing-grade Si3N4. Phase II will address further lowering of the cost of manufacture of substrates and designing economical methods for SiC coating of balls in fluidized bed CVD reactors. The CVD-SiC-coated balls and rollers to be developed will be used as bearing elements in hybrid ceramic bearings. Hybrid ceramic bearings, in turn, will be used in the machine tool industry where the low density of the ceramic elements can lower the centrifugal thrust forces, in the chemical process industry to take advantage of the corrosion resistance of the SiC elements, and moderate temperature applications. Cam followers in the automatic industry is another potential area to exploit the CVD-SiC coated rolling elements.