Design of GH4169 diaphragm for combined improvements of yield strength and surface roughness

Diaphragm compressors have become the primary source of on-site hydrogen compression for hydrogen fuelling stations around the world. The most common hydrogen-compressor-failure mechanism has been identified as diaphragm fracture due to low tensile strength and poor surface properties. In this study, a new type of GH4169 diaphragm with high yield strength and low surface roughness was fabricated. Microstructures, tensile behaviours and surface properties of the specimens were characterized by using scanning electron microscopy, an electronic universal testing machine and atomic force microscopy, respectively. The evolution of the gamma '' and gamma' phases with temperature has been examined. Both gamma '' and gamma' phases were precipitant-strengthened phases for GH4169 and the volume and size of gamma '' and gamma' phases increase with ageing time. In addition, the gamma '' phase is the main strengthening phase and gamma' is the supportive strengthening phase. Tensile strength was increased due to the strengthening phases at the cost of ductility. The roughness of the diaphragm could reach an arithmetic average roughness (Ra) of 0.1 mu m by applying a cooling-assisted polishing process. This work improves the reliability and reduces the auxiliary steps and down-time for diaphragm compressors.