SBIR Phase I: Development of Tools to Determine the Effect of Powder Metallurgy (P/M) Manufacturing Parameters on Fatigue of Highly Loaded Gears

这个小型企业创新研究(SBIR)第一阶段项目将开发和验证一个支持制造创新的工具，特别是生产高负载汽车变速器齿轮的粉末冶金工艺。粉末冶金(P/M)工艺提供了成形能力和材料利用率的完美结合，使该技术成为制造高负荷汽车变速器齿轮的理想选择。粉末锻造和新近开发的表面致密化工艺将成形能力和关键区域几乎没有气孔的材料结合在一起，以克服粉末冶金材料的强度限制。然而，粉末冶金工艺具有高度的变异性，因此工艺参数的优化势在必行。该项目将进行滚动接触疲劳下的材料模型试验，这是齿轮的失效标准之一。该项目将对材料科学和加工产生更广泛的影响(商业意义)。该项目将提供研究滚动接触疲劳条件下裂纹萌生和扩展的能力。这将导致对恒定和可变压应力下裂纹形成机制和裂纹扩展的新的和更好的理解。它允许将通过显微硬度、断裂力学和显微组织分析等经典方法获得的材料性能与滚动接触疲劳强度相结合。它有助于更好地理解工艺变量、热处理参数和材料在实际操作条件下的行为的影响。本项目的重点是粉末冶金工艺。然而，结果将改变无气孔材料的齿轮和轴承的设计和制造方式。改进的齿轮和轴承将提高变速器的效率，从而间接降低能源消耗。

This Small Business Innovation Research (SBIR)Phase I project will develop and validate a tool to support a manufacturing innovation specifically, the powder metallurgy process to produce highly loaded automotive transmission gears. Powder metallurgy (P/M) processes offer an excellent combination of shape forming capability and material utilization, making the technology ideal for manufacturing highly loaded automotive transmission gears. Powder forging and recently developed surface densification processes combines shaping capability and nearly pore-free materials in critical areas in order to overcome strength limitations of the P/M materials. However, P/M processes have a high degree of variability, which makes optimization of process parameters imperative. This project will perform model testing of materials under rolling contact fatigue, which is one of the failure criteria of gears. The broader impacts (commercial significance) from this project will be on material science and processing. This project will provide the capability to study crack initiation and propagation under rolling contact fatigue conditions. This will lead to a new and better understanding of crack formation mechanisms and crack growth under constant and variable compressive stresses. It allows combining material properties obtained by classical methods such as micro-hardness, fracture mechanics, and microstructure analyses with rolling contact fatigue strength. It leads to a better understanding of the effect of process variables, heat treatment parameters, and material behavior under real operational conditions. The focus of this project is on P/M processes. However, the results will change the way gears and bearings of pore-free materials are being designed and manufactured. Improved gears and bearings will increase the efficiency of transmissions, therefore indirectly reducing energy consumption.