Defect and Diffusion Forum Vol. 430

Abstract: Hastelloy is a nickel-chromium-molybdenum-iron-based alloy and a member of the ‘superalloy’ family. Hastelloy has exceptional properties like high strength, wear resistance and high-temperature stress-corrosion resistance. Therefore, Hastelloy is used in gas turbines, power plants, metal injection molding, etc. Many industrial applications are related to the properties of the surface. Wettability is a key surface property that affects applications like lubrication, adhesion, coating, heat conduction, etc. Laser Texturing is an excellent method to modify the surface properties of materials like metal, polymers and ceramic. In the present study, a carbon dioxide laser created unidirectional textures on Hastelloy (C22, C276, X). Different sets of unidirectional textures were formed by changing the laser power and frequency. Various roughness parameters were compared for every laser parameter. In this paper, the effective change in wettability properties of Hastelloy (C22, C276, X) after the Laser texturing process for a range of power and frequency were studied under DI water and glycerol as test fluids. Results show that the contact angle of the test fluid increases as the laser power increases, and the contact angle decreases as the laser frequency increases for all three superalloys. The surface energy of a given set of samples was also measured using the recorded contact angle of DI water and Glycerol by the OWRK equation. Similar trends were found in surface energy for all three Hastelloy.

Abstract: The piston connecting rod is an indispensable in the internal structure of the automobile. As one of the important components in the internal combustion engine system, the piston connecting rod needs to meet the requirements of high fatigue and impact load resistance. Forged piston connecting rod can obtain high strength and fatigue resistance. In this study, the parting line, draft angle, forging tolerance, die fillet radius, shrinkage and scrap are considered in the design of forging die. The process parameters and die dimensions of the forging process of aluminum alloy piston rod are simulated by finite element analysis. The aluminum alloy piston rod with high dimensional accuracy is then forged according to the finite element simulation results.

Abstract: Due to the operating conditions of weld and calibrating rolls used in the production processes of large electric-welded pipes, their material is subject to stringent wear and abrasion resistance requirements at high temperatures. The limited capabilities of conventional Cr-Mn-Ni tool steels and open die forging technologies with heat treatment processes do not provide the required performance properties for large welded rolls. Therefore, the material of the product was replaced with Cr12MoV high-chromium steel. This required identifying the formation patterns of the fine grain structure of high-chromium steel in order to adjust the production technology with adaptation to the unique conditions and equipment (12.5 MN hydraulic forging press, heating and thermal furnaces) of the forging shop. The technology was offered, which included the development of modes from heating to heat treatment with intermediate two-stage forging from Cr12MoV steel ingots in two sets of combined dies. At the first stage, deformation with a low reduction ratio ε = 5% and a relative feed rate of 0.4 per pass was provided to break and refine the carbide mesh, and at the second stage, intense deformation with a reduction ratio ε = 15% was performed. Further practical application has shown that the durability of weld rolls made from the new material increases by 20–30%.

Abstract: This research aims to investigate the properties of elastohydrodynamic rotational lubrication analysis on journal-bearing systems. To simulate elastohydrodynamic lubrication on journal-bearing systems, the Elasto-Hydro-Dynamic (EHD) solver is combined with the Multi-Body Dynamic (MBD) solver to create MBD virtual environment with lubricant. The hydrodynamic lubricant is governed by using the Reynolds equation, whereas the elastic contact is governed using Greenwood and Tripp theories. The simulation is performed by changing the operating conditions such as the speed, load, and clearance between two surfaces. One can find these parameters’ effects such as film thickness, hydrodynamic pressure, and friction. The result shows that the friction induced by shaft speed is similar to the Stribeck curve on mixed lubrication regime. Consequently, the clearance, speed, and load will not only affect the friction but also affect the hydrodynamic pressure and film thickness.

Abstract: In view of the fact that the load on the transmission element under extreme pressure conditions is much greater than that used in traditional machine tools, the contact surface between the ball and the track must bear great stress. Furthermore, it will heat up due to friction after starting and running. These effects are prone to material deformation and fatigue damage, and may even lead to the disappearance of the lubricating oil film. They are prone to surface damage due to metal fatigue, and then a serious situation of large pieces of peeling occurs for the linear guides. In order to prolong the fatigue life of the machine tools, this study investigates the effects of the lubricants on the tribology properties under the extreme pressure for the induction-treated linear guides.

Abstract: Since the requirement of high dust-free levels, it is necessary to develop the technologies with anti-wear and low dust generation for drive elements that can be quickly printed. Polylactic acid and synthetic resins are often paired with each other for the 3D printed driven elements. To achieve "smooth friction", the adhesion wear under dry friction conditions should be reduced. To achieve a "high dust-free level", the anti-wear of the paired elements under higher speed friction should be improved to reduce the generation of abrasive dust. Therefore, wear of the 3D printed polylactic acid elements sliding against the synthetic resins at the high speed friction are investigated in this paper.

Abstract: The aluminum 5754 alloy is one of the widely used engineering materials in shipping, rivet making, tread plates and automotive industries. These engineering structures envisage variable loading conditions during their service. In addition to it, it is also experiencing seismic vibrations. Hence, the engineering components made from such aluminum alloy are susceptible to fatigue fracture. In the current study, the prediction of fatigue crack growth (FCG) in 5754 aluminum alloy was made using the exponential function. The beam specimen comes up with a cross-section of 25X25 mm², a span length of 300 mm with a mechanical notch length of 2.70 mm at the centre was subjected to four-point bending (FPB) employing hydraulic INSTRON 8800 tensile testing apparatus. The periodic loading condition deformed the material up to large plastic deformation. The applied load was further down the elasticity of the material. The experimental data provided the relation between crack length (a) to the number of cycles (N) to failure. The response surface methodology (RSM) and modified exponential equation were used to predict the FCG. In RSM, when “stress intensity factor (K)” and “number of the cycle (N)" were considered independent variables, the response (a) was optimum (maximum) as compared to when “stress intensity factor range (del K)” and “fatigue crack growth rate (da/dN)” were considered independent variables. Hence, for designing the aluminum 5754 alloys as engineering structures, it was the number of cycles which provides a safe design as compared to da/dN. The modified exponential equation using an exponential function predicted the FCG for aluminum 5754 alloy in the form of a beam specimen. The anticipated results agreed with experimental data as the prediction ratio was 1.20 and the % deviation was 3.7.

Abstract: In mechanical equipment interacting with impingement particles, worn surface morphology of parts and components is formed by an accumulative action of a large number of single-particle erosions. To exhibit the mechanism of multi-particle erosion of target, three physical experiments and Discrete Element Method (DEM) simulations of erosion of iron target by the two vertical impingements of Al₂O₃ particle are carried out under three different landing errors x of the two impingements. The experimental results showed that each of two overlapping worn morphologies by the two impingements has an spherical cap shape. When x is larger than radius R₁ of worn morphology of target by the first erosion, two morphologies with an spherical cap shape are very close in size; while the size of worn morphology by the second erosion increases with the decrease of x, when x is smaller than R₁. The predicting worn morphologies by DEM are almost consistent with the experimental results, where the maximum relative deviation in size of worn morphology is 2.98% in the direction along x, and is 3.93% in the direction perpendicular to x. All these proved the effectiveness of the DEM model in predicting erosion of target by two impingements of particle.

Abstract: In the present work, NaBi(MoO₄)₂ (NBM) phosphor has been successfully synthesized by doping 1.0 mol% of Eu³⁺ via the conventional solid state reaction technique. The undoped synthesized NBM sample and 1.0 mol% Eu³⁺ doped phosphor were characterized to explore crystal structure, morphology, photoluminescence (PL) and colorimetric properties using various characterization techniques. The structural properties were analysed via x-ray diffraction and diffraction peaks were compared with the standard JCPDS (card no. 79-2240) pattern. The morphological studies of the sample have been done through FE-SEM micrograph. From the photoluminescence emission spectra, it has been observed that an intense peak was obtained in the at 615 nm under blue excitation. Colorimetric property of 1.0 mol% of Eu³⁺ doped NBM phosphor has been investigated and traced in the red region with high color purity of 92.79%. The aforementioned characteristics demonstrate that the NaBi(MoO₄)₂: 1.0Eu³⁺ phosphor has great potential in the field of w-LED applications.