A laminated and diffusion welded turbine vane with fine cooling passages was designed and manufactured using 18Cr-8Ni stainless steel wafers. The turbine vane produced, was assessed using coolant flow analysis.
In order to improve the joint quality, investigations were carried out using conventional diffusion welding to join the stainless steel wafers and camparisons made with diffusion welding followed by hot isostatic pressure (HIP) treatment.
The tensile strength of the diffusion welds increased as the welding pressure was raised. However, the use of higher welding pressure brings about large deformation at the joint. As a result it is difficult to use conventional diffusion welding to produce good quality joints without deformation of the cooling passages at the joint region.
When the welding area ratio at the joint interface is approximately 50% only isolated voids remain at the joint. Therefore, the use of HIP treatment is able to remove residual voids from the joint interface without macro deformation of the turbine vane. The use of HIP treatment allows joints to be produced with greater than 50% welded area ratio and with only 0.5% change in total length.
This study has shown that by applying HIP treatment after preliminary diffusion welding it is possible to produce joints with no residual voids and with a minimum change in component shape.
