Study on the Shear Angles in High Speed Machining of Powder Metallurgy Superalloy

High efficiency and high speed are the development directions of modern manufacturing technologies. In the last two decades, high speed machining is successfully applied in cutting steel and alumina alloy, due to its unique advantages. However, it is not yet prevalent in powder metallurgy (PM) superalloy machining. This work focuses on the shear angles and influencing rules in high speed machining PM nickel based superalloy, in order to provide reliable theoretical and practical methods in high efficiency/speed machining this kind of material in production practice.

Effects of Heat-Treatment Residual Stress on Low Cycle Fatigue Life of a Turbine Disk in PM Superalloy

Turbine disks in powder metallurgy (PM) superalloy have been widely used in advanced aeroengines. The production of PM superalloy turbine disks involves a series of heat treatment processes, which would inevitably create residual stresses. It has been proved that the low cycle fatigue (LCF) life of the turbine disk is affected by the residual stresses. The computational simulation of heat treatment is considered as an effective way to evaluate the residual stresses in a turbine disk. A finite element software was used to simulate the heat-treatment processes of a FGH95 turbine disk to obtain the residual stress field. To investigate the relaxation of residual stress in FGH95, smooth bar specimens were measured by X-ray diffraction before and after being loaded. Modified by the residual stresses, SWT model is used to predict the low cycle fatigue life of the turbine disk modified by the residual stress field obtained from the simulation of heat treatment. By the comparison between the prediction modified by the residual stress and the prediction without modification, a considerable decrease in low cycle fatigue life is indicated.

Determination of the Content of Ultra-Low Sulphur in PM Superalloy FGH96 by Infrared Carbon-Sulphur Detector

PM Superalloy FGH96 is usually used as turbine disc materials. It is a kind of alloy with high purity, which has strict demands of the content of impurity elements, especially the element of sulphur. Because sulphur is accumulated in the grain boundary of manganese or iron, with the form of sulfide, it has great impact on the performance of PM Superalloy FGH96, such as toughness and fatigue property. Therefore, it is an important part of quantity control to detect accurately of the content of ultra-low sulphur in PM Superalloy FGH96. As the market demand of PM Superalloy FGH96 and quality becomes varied, it is a trend that PM Superalloy FGH96 has ultra-low content of sulphur (S: 0.0001%-0.0020%). Hence, the related analysis techniques are needed. A new method of analyzing Ultra-low Sulphur (S: 0.0001%-0.0020%) in PM Superalloy FGH96 is established in the article by selective experiments with relevant test conditions, such as combustion conditions and blank test, using infrared carbon-sulphur detector.