Papers by Keyword: Waspaloy

Abstract: Grinding machines that employ a high-speed reciprocating worktable or wheel head are known as high-speed reciprocation grinding. Grinding heat generated in the high-speed reciprocation grinding process is low. Therefore, it is considered that the high-speed reciprocation grinding is suitable for grinding material of low thermal conductivity. In this study, the high-speed reciprocation grinding is applied to grind nickel-based super alloy “Waspaloy” which is known as difficult-to-cut material. And grinding characteristics of Waspaloy are investigated. As a result, it is found that the effect of grinding heat is smaller than the effect of grain depth of cut in grinding process of Waspaloy.

Abstract: Machining of advanced aerospace materials have grown in the recent years although the difficult-to-machine characteristics of alloys like titanium or nickel based alloys cause higher cutting forces, rapid tool wear, and more heat generation. Therefore, machining with the use of cooling lubricants is usually carried out. To reduce the production costs and to make the processes environmentally safe, the goal is to move toward dry cutting by eliminating cutting fluids. This objective can be achieved by using coated tool, by increasing cutting speed and by improving the product performance in term of surface integrity and product quality. The paper addresses the effects of cutting speed and feed on the surface integrity during dry machining of Waspaloy using coated tools. In particular, the influence of the cutting conditions on mechanical power consumption, the tool wear and some important indicator of the surface integrity (surface roughness, affected layer, microhardness, grain size and microstructural alteration) were investigated. Results show that cutting conditions have a significant effect on the parameters related to the surface integrity of the product affecting its overall performance.

Abstract: Inconel 718 and Waspaloy superalloy was vacuum brazed using BNi2 filler. The effect of joint clearance and brazing temperature on the interfacial microstructure, element and microhardness distribution were studied systematically. The microstructure of the brazed joints is both mainly solid solution when the brazing clearance is 30μm at 1080 °C and 100μm at 1140 °C. The results show that the elements diffusion of nickel based filler is more active with the decrease of the joint clearance and increase of brazing temperature. The peak of microhardness is shown at the centerline of brazing seam.

Abstract: An assessment of the inhomogeneity of microstructure generated within plane strain compression test specimens has been performed using the nickel based superalloy, Waspaloy. Two variables were investigated: the effect of strain rate and the effect of friction at the tool/specimen interface. Tests were performed at 1040°C at nominal strain rates of 0.01 and 1 s-1 with and without a glass based lubricant. At the low strain rate the microstructure was relatively homogeneous regardless of the friction conditions. At the high strain rate there was significant microstructure variation from surface to mid plane which was further exaggerated by increased friction. Quantification of the inhomogeneity, however, is non-trivial in this alloy due to the complicated recrystallisation behaviour it exhibits and difficulty in differentiating between recrystallised and non-recrystallised grains.

Abstract: The purpose of this study is to investigate the high temperature creep life of Waspaloy using the Initial Strain Parameter Technique (ISPT). The creep tests were performed at the elevated temperatures from 550oC to 700 oC. Constant stress creep tests were carried out in the experiment. The initial strain was measured for one minute after loading. The creep life of Waspaloy was calculated using the creep life prediction equation of ISPT. The confidence level between the experimental rupture time and the calculated rupture time using the ISPT is within 95%. So, the results show that the creep life prediction by the ISPT was a good agreement with LMP method.

Abstract: A methodology for evaluating and predicting component lives in creep-fatigue interaction region was investigated for Waspaloy. A unified viscoplasticity constitutive equation including multi-back stresses was used to describe cyclic material behaviors. Also, a continuum damage model coupling with the creep-fatigue damage rules was established based on the analysis of creep and low cycle fatigue behavior. Multi-axial fatigue and creep equivalent stress concepts were employed to predict three dimensional component lives. Notched cyclic tests under various stress conditions in the creep-fatigue interaction region were carried out to validate the life prediction methodology with FEM simulation based on the continuum damage model. The comparison of experimental data and prediction results indicates that the continuum damage model is a powerful approach for the prediction of component lives.

Abstract: Non-destructive evaluation (NDE) techniques offer the potential advantage of achieving fast throughput microstructural characterization as well as monitoring that could be extremely valuable in assessing the mechanical integrity of turbine engine components. It is well known that the γ′ precipitate size and distribution can often determine the mechanical strength of nickel base alloys. In this investigation, Waspaloy, an age-hardening superalloy, was chosen as the candidate to produce varied microstructures, which were subsequently characterized via the DC four-probe resistivity method. Specimens with average grain sizes of 13, 52 and 89 μm were obtained upon solutionizing at 1045°C, 1090°C and 1145°C respectively. The specimens were annealed at 1045°C to stabilize the vacancy concentration prior to aging at 800°C for times ranging from 0.1 to 100 hours. Sub-grain microstructures examined in the SEM showed progressive growth of γ′ precipitates with increased aging duration in all cases. The measurements of DC four-probe resistivity showed a consistent drop in the resistivity with increased aging time, which was concurrent with the growth of the precipitates.