Papers by Keyword: Super Alloy

Abstract: Nickel superalloys are being used in applications subjected due to its excellent creep and oxidation behavior. The CM247LC nickel based super alloy is considered due to its exceptional combination of high-temperature strength, creep resistance, oxidation/corrosion resistance, and mechanical properties suitable for applications, particularly in the aerospace industry. Though, unfavorable tribological behavior is primary challenge in gas turbine applications. Nickel-based superalloy CM-247LC was manufactured through laser powder bed fusion process under two different conditions. X-ray diffraction analysis (XRD) was carried out to study phases present in as built CM247LC alloy. Microhardness and tribological characteristics were investigated on the as built alloy. XRD spectrum was predominantly observed with γ and γ′ peaks. Presence of γ′ and MC carbides offered strengthening to the as built CM247LC alloy which enhanced the hardness and tribological properties. The wear rate of samples gets increased with increase in load applied during the wear test. Worn out surfaces were examined and it is observed that the predominant type of wear mechanisms as adhesion and abrasion.

Abstract: In this study, a series of deep micro holes were machined on thick GH4169 super alloy by the trepan drilling, using a millisecond pulsed laser which equipped to the numerical control processing system. The microstructure of the holes including surface and longitudinal morphologies, diameter, taper, circularity, micro cracks and recast layer were systematically characterized. The surface morphology and the longitudinal section of the drilled holes were observed by Scanning Electron Microscope and 3D Laser Scanning Confocal Microscope. The method of Minimum circumcircle method was employed to evaluate the entrance and exit end circularity. The results showed that the melt and spattering accumulating around the holes decreased with the augment of laser power. The diameter of the entrance showed an increasing tendency with the growing of laser power, but the exit end was not seriously affected by the power. The micro cracks and recast layer could be found obviously, the micro cracks appeared in those zones which thermal stress concentrated, the thickness of recast layer is about 20μm and the taper and circularity were optimized at a laser power of 80-100W.

Abstract: Both superalloy GH2135 and stainless steel 420J1 were used as test materials to be processed by LASERTEC 80 PowerDrill three-dimensional solid laser processing center. The microstructure of the hole was investigated by super depth of field microscope and laser scanning microscope. The front and back orifice diameter, orifice deposits and thermal effect of accumulation zone were studied. The single factor test method was used to study the influence of pulse energy, pulse width and repetition frequency on the quality of micro holes. The results showed that the front and back diameter of the holes all increase with the increase of pulse energy from 0.4J-3.9J. And the front and back aperture are increase with the increase of pulse width from 0.9ms-1.9ms. Meanwhile, the variation of the aperture and pore taper is more noticeable with the repetition frequency changed from 10Hz-60Hz. The results revealed that pulse energy is one of the biggest influence factors, large pulse energy can lead to small hole taper within a certain range, and short pulse width can reduce orifice debris and splash. Both the recast layer and microcrack were existed in the two kinds of metal materials. The quality of holes drilling in GH2135 is better than 420J1.

Abstract: Interface reactions and wettability between melt superalloys and ceramic mould materials were investigated by using a sessile drop experiment. The wetting angle of the melt alloy on the ceramic material was calculated and the microstructure of the alloy interface was investigated by metalloscope as well as SEM. It was found that active element C in the alloy is an important factor that influences the interface reactions and the wettability. Alloys with C content lower than 0.07wt.% were almost stable on the ceramic material and no interface reaction products were found. However, alloys with C content higher than 0.16wt.% reacted with the ceramic materials. Purple reaction products were found on the alloy surface and sand adhesions were observed at the alloy-ceramic interface. In the non-reactive system, the wetting angle is in the range of 135^o-150^o. In the reactive system, the wetting angle is lower than 120^o.

Abstract: Inconel 718, a Nickel based superalloy is widely used for aerospace applications mainly due to its high temperature resistance and high strength to weight ratio. Its poor machinability is a limiting factor in commercial, cost intensive applications. This paper investigates the machinability of Inconel 718 in high speed drilling. The impact of the material on thrust forces, torque and chip microstructure have been measured at four different cutting speeds – 19, 27,43 and 67 m/min. The high tensile strength coupled with low thermal conductivity compounds the machining process. The thrust forces decrease with cutting speed, but the torque fluctuates at intermediate cutting speeds. Chip formation is continuous across cutting speeds, with thin cross sections and evidence of saw tooth edges. Inconel work hardens more than titanium alloys and shows good ductile to brittle transition at low temperatures creating chips of lesser length as observed using scanning electron microscopy.

Abstract: Linear-elastic fracture mechanics based technique was used to measure the fracture toughness in terms of K1C of a solid solution super alloy. Due to thermal fatigue and high temperature exposure for various application of Alloy 617, it was demanded to measure crack growth behaviour of this alloy. Pre-cracked compact tension (CT) specimens ware used to determine the crack growth rate (CGR) of alloy 617 by direct current potential drop (DCPD) in-situ crack monitoring technique. Artificial Neural network (ANN) statistical model computed different fracture parameters from experimental inputs by feeding information to the network. This feed-forward network calculated the threshold fracture toughness, number of cycle to failure, slope of the Paris curve for the alloy at different temperatures and load ratios. The computational model correlates and converges with the experimental results with a maximum deviation of 6%. Thus, the model is recommended for complex and stochastic application of the nickel base super alloy 617.