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

这项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。结合热等静压（HIPed）或烧结和HIPed氮化硅元素（球或滚子）的混合轴承在机床工业，化学加工工业，真空泵，气相沉积和分子束外延设备以及离心机和高速测试设备中表现出优异的性能。尽管表现出这种业绩，但含氮化硅元素的全球市场总额小得令人沮丧（1995年为- 2 500万美元）。限制氮化硅使用的最重要因素是成本。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增韧的SiC轴承表面将具有所需的显微组织均匀性和表面韧性，从而以更低的成本提供与氮化硅相当的滚动接触疲劳和耐磨性。SiC承载元件的成本应低于Si3N4，因为粉末、加工和表面处理的成本较低。与Si3N4相比，SiC元素具有优越的耐腐蚀性和抗氧化性，因此有望在恶劣环境中表现出更好的性能。第一阶段的具体目标是：(1)通过调整无压烧结SiC- tic基板的热膨胀来优化SiC涂层中残余表面压缩的大小，(2)建立最佳的CVD条件以避免有害的涂层子结构，以及(3)在RCF测试中证明SiC的寿命和耐磨性可与当前轴承级Si3N4相媲美。第二阶段将进一步降低衬底的制造成本，并设计经济的方法在流化床CVD反应器中对球进行SiC涂层。开发的cvd - sic涂层球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工业，其中陶瓷元素的低密度可以降低离心推力，在化学加工工业中利用SiC元素的耐腐蚀性和中等温度应用。自动化行业的凸轮从动件是开发CVD-SiC涂层轧制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.