Turbine Blade Residual Core Detecting With Neutron Radiography

Neutron radiography is an NDT technology since 1960 s. Neutron radiography is similar to conventional radiography in principle, however there is significantly different in the absorption characteristics. The two radiographic technology are complementary in application. Because the sensitivity of X-ray radiography detecting turbine blade residual core is low and the residual core is easy to leak, this paper was carried out research of neutron radiography inspections of turbine blade residual core.At present, there is no relevant standards of neutron radiography in China. The ASTM E545 has been analyzed in this paper. Two basic indicator for neutron image quality assessment is BPI and IQI from the ASTM E545. The neutron image quality is divided into five grades. The neutron image quality of residual core must be at least up to NC-H-G-I image quality of ASTM E545 regulation.In this paper, the Monte Carlo method was used to simulate thermal neutron radiography detecting turbine blade residual core. A step bar block was designed to test turbine blade contrast sensitivity. The results show that simulation and practical radiography is very proximate in detecting ability. MCNP method can accurately predict neutron detection result and as important role for guiding the thermal neutron radiography research.The ceramic core were tagged with 1%~5% Gd2O3 as tracer to improve neutron radiography image contrast. Three groups different thickness contrastive specimen was prepared. The main determinant of neutron radiography inspection of turbine blade residual core sensitivity are thickness of the core, concentration of tracer Gd2O3 and thickness of the blade. The experiment result shows that when the ceramic core tagged with 1% Gd2O3 as tracer, 0.2mm thick core can be detected on 4mm thick DD6 alloy. The tracer Gd2O3 is more appropriate at 3% to 4% in actual detecting.