Erosion Mechanisms and Performance of Cellular Ceramic Substrates

High emission performance standards and precious metals costs have pushed the catalytic substrate toward high cell density and thin wall, such as the 600/4, 600/3 and 900/2 products. Due to the inherently lower mechanical strength of these products, coupled with a shift from underbody to close-coupled placement, a concern was expressed that the severe thermal and mechanical conditions may cause structural damage to the substrate, which in turn could impact the catalyst performance. One source of reduced performance during use is the loss of catalyst due to erosion. A previous study¹ indicated that the existence of particulate in an air-stream could cause substrate erosion. However, it was not clear if other factors could contribute to or accelerate the erosion process. In order to address this question, experiments were performed to examine the influence of high velocity flow, temperature, impingement angle, particulate characteristics, and coating effect on erosion. Based on the experiment data, it was verified that the erosion phenomenon requires the presence of particulate in the exhaust stream. The magnitude of the erosion was dependent on the particulate velocity, size, morphology and impingement angle. Web orientation must also be considered when dealing with conditions that deviate from normal flow. Erosion was reduced by the addition of temperature.