Normal Impact Angle Research Articles

Experimental and numerical studies on the effectiveness of high-strength steels protecting against API BZ projectiles

ABSTRACT This paper uses numerical and experimental methods to look at how well Xar450 and Perform 700 high-strength steels protect against a 7.62 × 39 mm API BZ projectile. The numerical study of the target thicknesses varies from 3 mm to 4 mm and 6 mm. And they are struck at 0°, 15°, 30°, 45°, and 60° oblique angles. Numerical simulation results show that at a normal impact angle, the bullet can break through the Perform700 targets in all thicknesses; however, the resistance performance of the target plate increases with the rise of oblique angles. The Xar450 target plates of 4 mm and 6 mm can resist the bullet at any oblique angle, but the bullet can easily penetrate 3 mm thickness from 0° to 30° oblique angles. The experiment is based on the VPAM-APR 2006 standard. The experiment results showed that the bullet perforated through the Perform700 target plate with a thickness of 3 mm at 0° and 30° oblique angles. In contrast, the bullet cannot penetrate the Xar450 target thickness of 4 mm at a normal angle. The findings of this research are used in the formulation of the design methodology for a light armoured vehicle. Besides, they have considerable importance in the realm of calculating and developing anti-fracture structures for practical applications.

Investigation of aqueous slurry erosion-corrosion behaviour of Tantalum in different pH solutions

Erosion-corrosion behaviour of pure Tantalum (Ta) was investigated using corrosive slurry solutions (pH 4, 7, and 10) containing 7 wt% SiC as erodent particles. Tests were carried out using an impinging jet erosion-corrosion apparatus with a jet velocity of 5 ms−1 and at two impact angles (30° and 90°). Under particle bombardment conditions, a marked reduction in corrosion resistance offered by Ta was observed amid a significant cathodic shift in the ECorr values for all pH values investigated. Results showed that interaction between erosion and corrosion was higher under 30° impact leading to a higher rate of material removal. On the contrary, negative synergism was observed for experimental conditions of normal impact for pH 7 and pH 10. Scanning electron microscopy studies revealed typical ductile erosion mechanisms of material removal which consisted of dominating micro-cutting for 30° and plastic deformation resulting in lip formation for normal impact angle. These appeared to be assisted by dissolution of weakened areas and passive layer removal as corrosion mechanisms. Potentiostatic erosion-corrosion experiments were utilised for calculation of synergistic and antagonistic effects and have been presented in the paper.

Deformation and film formation mechanisms during high velocity impact of silicon carbide nanoparticles

Molecular dynamics simulations were conducted to study the factors that affect deformation behavior that occurs during high-speed impact of SiC nanoparticles onto flat substrates. For these simulations, a 6 nm particle was impacted onto a (110)-oriented SiC substrate and the particle impact velocity (3000–4000 m/s), particle orientation, and impact angle (0°–75°) were systematically varied. A broad range of impact behaviors were observed and categorized from elastic with no particle sticking to plastic with significant particle deformation and sticking. High impact velocities and near normal impact angles were found to enhance particle sticking. Particle orientation also had an effect. For some impact conditions, disordering of the lattice within the particle was observed and quantified. Particle impacts that resulted in the greatest degree of amorphization also exhibited significant deformation. This suggests that amorphization followed by viscous flow in the disordered region of the particle is the primary deformation mechanism responsible for particle sticking.

Predicting metallic armour performance when impacted by fragment-simulating projectiles – model review and assessment

Metallic targets impacted by blunt-nosed, fragment-simulating projectiles typically fail via shear plugging. A number of models exist in open literature to predict the onset of this failure mode, which can be used to determine the ballistic limit velocity, VBL, for a particular combination of projectile and target plate. A set of nine existing penetration models for blunt projectiles were identified and reviewed for their ability to predict the plugging-mode ballistic limit velocity of monolithic titanium alloy, aluminium alloy, and steel alloy plates impacted by blunt-nosed, fragment simulating projectiles. A database of more than 650 experimental ballistic limit measurements was used to evaluate the performance of the predictive models, covering a wide range of ordnance and sub-ordnance velocities, normal and oblique impact angles, and target plate thicknesses. The range of experimental data typically exceeded that for which the applied models were derived or previously validated. Nonetheless, it was found that all nine models could predict the experimental ballistic limit to within +/- 50% of the experimental measurement for more than 50% of the ballistic tests considered.

Effect of Graphene Enrichment on Solid Particle Erosion Performance of Electroless Ni-P Composite Coatings

Abstract Solid particle erosion (SPE) and dents (from contact loads) are among numerous surface degradations in the hydrocarbon industry that can in turn compromise the longevity of protective coatings. Both these degradation mechanisms can induce cracks that allow the corrosive solutions to seep through those cracks and corrode the underlying metal, thereby defeating the purpose of surface protection. Nickel-phosphorus (Ni-P) coatings have been known for decades for their corrosion resistance, but their applications in hydrocarbon industries are impeded by their tribological limitations, namely low wear resistance. In the current research work, graphene nanoplatelets were introduced to an Ni-P electroless plating bath in various concentrations (30 mg/L, 60 mg/L, and 100 mg/L) to achieve three different compositions of ternary Ni-P–graphene coatings, namely Ni-P-30 mg G, Ni-P-60 mg G, and Ni-P-100 mg G, respectively. Surface roughness was characterized via topography employing a laser confocal microscope. Coating hardness was characterized using Vickers hardness and the composition analyses were carried out via energy dispersive spectroscopy. SPE was conducted via Tungsten carbide (WC) erodent ball at three different impact angles and two different particle velocities. Finally, Hertzian indentation was performed under two different loads to characterize the denting behavior of coatings. Eroded and dented coatings were further visualized via an optical microscope. The highest concentration of graphene (by 18 vol.%) in Ni-P-30 mg G coating improved the hardness, leading to the smallest size of indents during both SPE and Hertzian indentation. Also, Ni-P-30 mg G exhibited no evidence of cracking under normal impact angle and particle velocities of 35 ms−1 and 52 ms−1.

Investigation of solid particle erosion behaviour of SS-304 under different conditions

Erosion is a multifarious phenomenon and observed to be the major cause of failure of many engineering systems including aircraft engines, power generation units and industrial equipment. In the current study, erosion tests were carried out on SS-304 steel by utilizing an air jet erosion testing rig. The erosion behaviour of austenitic stainless steel (SS-304) at different temperatures (room temperature, 200 °C and 400 °C) was evaluated. The effect of impingement angle of erodent particles on erosion mechanism was also determined. It was observed that the erosion rate of steel was higher at room temperature and decreased gradually with increase in temperature up to 400 °C. The erosion rate was also observed to be high at oblique impact angle (30°) as compared to normal impact angle (90°) indicating the ductile mode of erosion. Further scanning electron microscopy with Energy Dispersive Spectroscopy (SEM-EDS) attachment was utilized for surface characterization of eroded samples. The eroded samples show the development of lips and craters which results in plastic deformation of material.

Erosion of polymers and polymer composites surfaces by particles

Surface erosion due to solid particle impact is a major concern in engineering applications of handling solid-particulate flow. A semi-empirical model is developed for numerical erosion simulation of polymers and polymer composites. The novelty of the developed model is the correct capturing of the angle of maximum erosion for different erosion modes of polymeric materials and relating it to measurable mechanical properties of the target materials. The model incorporates both the material removal due to elastic–plastic collision of the particles at oblique and normal impact angles. The oblique impact model is derived for ploughing and fracture governed mechanisms of material removal. A simplified correlation is used to consider the relative effect of each mechanism on the total erosion at oblique impact angles. The model indicates the variation in velocity exponent to the mechanism of material removal. The theoretically derived model for single-particle impact is correlated to the available experimental results of multi-particle impacts through the empirical coefficients. The predictions are in good agreement with the extensive literature data for polymers and polymer composites. Further, to propose a single model of erosion for polymer and its composite, the relationship between the empirical coefficients in the developed model and the target material properties is established.

Microstructure and high temperature erosion behavior of laser cladded CoCrFeNiSi high entropy alloy coating

In this study, CoCrFeNiSi high entropy alloy (HEA) coating without pores or slag defects was prepared on 304 stainless steel surface by laser cladding. Thermodynamic parameters of CoCrFeNiSi HEA were calculated. Microstructure and phase composition were analyzed by means of scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Comparative studies on hardness, high temperature erosion and oxidation performances were conducted between the CoCrFeNiSi HEA and Stellite-6 Co-based alloy coatings. The results show that laser cladding CoCrFeNiSi HEA coating was composed of single FCC structure. Typical metallurgical bonding between cladding coating and the substrate was formed. Microhardness of CoCrFeNiSi HEA coating reached to approximately 580HV0.2, which was higher than that of Co-based alloy coating (485HV0.2). There was little surface hardness reduction at 500, 600 and 700 °C for CoCrFeNiSi and Co-based alloy coatings. Erosion tests were conducted using quartz sand particles at 20, 500, 600 and 700 °C with an impact angle of 30, 60 and 90°, respectively. The HEA coating showed comparatively lower erosion rates than Co-based alloy coating under all test conditions. The erosion morphologies of both coatings showed that ploughing and micro-cutting were the two primary erosion mechanisms at oblique impact angles, while the erosion mechanism was replaced by the formation of craters and platelets at normal impact angles. A dense and continuous oxidation film could form on HEA coating at 700 °C which may protect the coating from erosion at high temperature to some extent.

Solid particle erosion behavior of melt-infiltrated SiC/SiC ceramic matrix composites (CMCs) in a simulated turbine engine environment

The erosion behavior of a melt infiltrated SiC/SiC ceramic matrix composite was investigated under a more representative engine environment. A special experimental facility was setup to simulate the turbine engine conditions. The influence of the operating parameters such as particle velocity, particle size, temperature, erodent concentration and impingement angle were investigated. In addition, room temperature studies were also conducted under the same operating parameters for comparison. Eroded sites were investigated under the scanning electron microscope (SEM) to understand the erosion mechanisms. The results indicate that erosion rate increased with increase in particle velocity, size and temperature. Also, at shallow impact angles the CMC shown to exhibit ductile like mode of erosion as opposed to brittle fracture mode at normal impact angles was observed. The erosion rate decreased with increase in erodent concentration which may be related to a particle shielding effect.

Influence of thickness of hydrophobic polytetrafluoroethylene (PTFE) coatings on cavitation erosion of hydro-machinery steel SS410

Hydrophobic materials have the potential to replace the existing surface modification materials to combat the problem of cavitation erosion (CE), owing to their various capabilities like self-cleaning, anti-corrosion, anti-fogging, anti-icing, anti-fouling, and drag-reduction. Polytetrafluoroethylene (PTFE) as a hydrophobic material exhibits specific combination of properties such as low friction coefficient, chemically neutral, good impact strength and considerable thermal firmness, that allow PTFE to be used in a wide range of applications. Therefore, in this work, an effort has been made to explore the effect of thickness of hydrophobic PTFE coatings on CE of the hydro-machinery SS410 steel. Hydrophobic PTFE coatings with three variable thicknesses have been prepared on the hydro-machinery SS410 steel using sintering process. Using high-velocity submerged water jet cavitation erosion test rig, CE behaviour of PTFE coated and bare SS410 steel was evaluated under various combinations of operating parameters: namely jet velocity, stand-off distance (SOD), and impact angle. Contact angle was reported to be increased with the decrease in the thickness of PTFE layer, which may be due to the increased surface roughness of PTFE layer with decrease in thickness. CE resistance of PTFE coated material with a maximum thickness of 121 μm, was found to be highest for all the combinations of operating parameters, which may be attributed to its lowest fracture toughness and better cushioning effect. Further, it was observed that CE of the coated and SS410 steel was found to be maximum at the chosen maximum velocity, normal impact angle, and intermediate SOD. The signatures of pits with circular and elongated morphology were observed for normal and shallow impact angles, respectively. In case of lowest PTFE layer thickness, overlapped pits with relatively higher depth were observed, which might be responsible for higher CE of the same amongst all the PTFE coatings.

Slurry Erosion–Corrosion of Bimodal Complex Concentrated Alloy Composite Cladding

Herein, bimodal‐reinforced AlCoCrFeNi complex concentrated alloy composite cladding on stainless steel 316L substrate using microwave hybrid processing is synthesized. Detailed microstructural analysis of the claddings shows the presence of cellular structure A2 (disordered BCC) with intermetallics (B2 (ordered BCC) and σ phases) at the intercellular regions. The presence of Cr23C6 is also observed for the reinforced claddings due to the dissociation of the SiC particles. The bimodal‐reinforced cladding shows the highest hardness (in excess of 800 HV) and fracture toughness (≈12 MPa√m), followed by micro‐ and nanocomposite claddings. Under slurry erosion condition, the bimodal composite cladding exhibits 10 times better erosion resistance than stainless steel 316L and nonreinforced cladding (1.5–2 times), respectively, at oblique angle followed by nano‐ and microreinforced unimodal counterparts. The outstanding performance of the bimodal composite cladding under both test conditions is related to higher hardness, fracture toughness, and resistance to plastic deformation. The detailed analysis of the eroded samples shows microcutting and ploughing as a dominant mechanism at an oblique angle while platelets, cracks, and microindents being the contributing factors for erosion at the normal impact angle.

Effects of flow velocity and impact angle on erosion-corrosion of an API-5 L X65 steel coated by plasma nitriding of hard chromium underlayer

In this study, the erosion-corrosion behavior of an API-5L-X65 steel coated by plasma nitriding of hard chromium underlayer has been investigated as a function of flow velocity (4, 5, 6, 7.5m s−1) and impact angle (30°, 45°, 60°, 90°) by a slurry of 3.5wt.% NaCl, and 3wt.%SiO2. The structure and microstructure of coating were characterized by X-ray diffractometry and scanning electron microscopy techniques. The maximum of mass loss was at the impact angle of 45° which the degradation slightly decreased with the increase of impact angle. However, the maximum degradation of the CrN coated samples occurred at normal impact angle. The analysis of erosion-corrosion mechanism showed the erosion process was more effective than corrosion.

Tailoring of surface topography for tribological purposes by controlled solid particle impacts

This study proposes a novel, cost-efficient and productive technique, Tribo-blast, to tailor surface topography for tribological purposes. Tribo-blast is based on mask-less micro-blasting with spherical or angular particles and precisely controlled process parameters. This approach enables rapid fabrication of μ-pockets (5–50 μm) on free-form surfaces comprised of any material. A particle with a new 3D geometry—a spinning top—is proposed to match the shape and dimensions of the irregular craters formed in a metallic target by an angular particle at the normal impact angle. The results were experimentally validated on stainless steel 316L, Co–Cr–Mo and Ti–6Al–4V alloys. A simple analytical routine allowed for control over the size, area, concentration and homogeneity of randomly distributed angular and spherical μ-pockets with <20% error. The Abbott-Firestone curve and texture ratio can be tailored according to one's intended design. The bearing index of the tailored surface was more than two times that of the lapped surface, and fluid retention was increased one hundred times. Thus, this approach is considered to be more productive, cost-effective and simple than current micro-texturing techniques.

Oblique impact of droplets on microstructured superhydrophobic surfaces

This paper studies the oblique impact of droplets on microstructured superhydrophobic surfaces with the lattice Boltzmann method. Three-dimensional simulations are performed based on the pseudopotential multiphase model, with the Carnahan-Starling equation of state and the multiple-relaxation-time collision operator adopted to overcome the numerical instability problems at high liquid/gas density ratio and low fluid viscosity. The droplet impact dynamics is simulated in a wide range of normal Weber numbers (0–30), Ohnesorge numbers (0.002–3), and impact angles (15°–90°), with particular interest in understanding different types of bouncing behavior and their effects on the contact time. The results show that, among the four possible types of bouncing identified in the simulation, including conventional retracting bouncing, incomplete-retracting bouncing, impaled retracting bouncing, and tumbling bouncing, incomplete-retracting bouncing and tumbling bouncing have less contact time and could be facilitated by increasing the impact obliqueness. The increase in the normal Weber number leads to a transition from conventional retracting bouncing, to incomplete-retracting bouncing, and then to impaled retracting bouncing. The contact time shows a non-monotonic trend of “decrease”-“increase”-“decrease” with enlarged Ohnesorge number, and the sheer drop in the contact time at high Ohnesorge numbers is due to the occurrence of tumbling bouncing.

Solid particle erosion wear on plasma sprayed mild steel and copper surface

Structural engineering components in plant made of mild steel and copper are affected by severe erosive wear due to presence of particulates in its surrounding. To protect these costly structural elements, we have taken atmospheric plasma spray process. This process is better for mild steel and copper due to several advance properties such as high temperature stability, coating efficiency, wear and corrosion protection. Coating by this process can be applied onto all suitable base materials with the widest variety of powders. In this investigation we have taken industrial waste like fly-ash, quartz and ilmenite powder as coating composite material and deposited on Mild Steel and Copper substrates with different weight proportions and different power levels of the plasma torch. Erosion type and their mechanism extensively investigated using scanning electron microscopy. Erosion properties have been studied using Air Jet erosion test Reg. with Silica erodent. Two significant parameters i.e. Erosion rate and Avg. microhardness have been measured by varying input i.e. power lever, velocity of erodent and time of erosion exposure. It is observed that, maximum erosion occurs at normal impact angle that indicates about brittle erosion condition. Different graphs are being plotted between mass loss-rate versus time period/impact pressure/impact angle, which gives good correlation with surface features observed. Based on these observations artificial neural network (ANN) models are developed to predict the result in various parameter setup.

The Effects of Constant Kinetic Energy of Different Impacting Particles on Slurry Erosion Wear of AA 6063

The present experimental study investigates the effect of constant kinetic energy on erosion wear of aluminum alloy 6063. Three different natural erodents (quartz, silicon carbide, and alumina) with different particle sizes are used to impact at 45 deg and 90 deg impact angles. For calculating the number of particles in the slurry pot, it is assumed that the solid particles are of spherical shape. The total numbers of impacting solid particles were kept constant by adjusting the solid concentration, velocity, and test duration. The scanning electron microscope (SEM) images of the three erodents show that the alumina particles have sharp edges with more angularity, and silicon carbide particles have subangular nature while quartz particles are blocky in shape. The mass loss per particle at 45 deg impact angle is observed higher than at normal impact angle. It may be due to the change in material removal mechanism with changing the impact angle. It is also found that the mass loss per particle from the target material having different particle size with constant kinetic energy remains constant for respective erodents. This indicates that the velocity exponent of impacting particles is around 2. The SEM images of eroded surfaces reveal the different mechanisms of material removal at 45 deg impact angle and at normal impact angle.

Efficiency of needle structure at hypervelocity impact

The paper presents a numerical investigation of an efficiency of a needle structure at a hypervelocity impact with a spherical projectile. A modeling was performed using a smoothed particle hydrodynamics method implemented in Ansys/Ls-Dyna explicit software and a verified model. We investigated hypervelocity impacts of the spherical projectile with needle structure at different initial velocities in the range of 4190–9200 m/s and both normal and oblique impact angle. The investigations revealed efficiency of a needle structure in comparison with a solid structure of the same mass at a normal impact angle. It was shown that the character of hypervelocity impact of the spherical projectile with needle structure did not change qualitatively when the impact angle changed, and the needle structure preserved its capability to resist a hypervelocity impact.

Erosion-wear and intergranular corrosion resistance properties of AISI 304L austenitic stainless steel after low-temperature plasma nitriding

In this paper, AISI 304L austenitic stainless steel has been subjected to plasma nitriding at 673 and 681 K lasted for 6, 18, 24, and 36 h. The morphology, microhardness, phase, and microstructure evolution of the nitrided layer were studied. Not only an expanded austenitic phase (γN) but also Cr-nitrides were formed in the nitrided layer. Transmission Electron Microscopy (TEM) study showed the formation of amorphous and nanocrystalline phases in the surface layers of the samples. The erosion-wear and intergranular corrosion (IGC) resistance behaviors of the nitrided samples were studied in detail. As compared to the non-nitrided sample, the erosion-wear resistance of the nitrided layer at normal impact angle doubles after nitriding at 673 K for 6 h, as a result of the formation of γN phase. Degree of sensitization (DOS) of IGC is gradually enhanced with the increase of nitriding time as indicated by a double loop electrochemical potentiokinetic reactivation (DL-EPR) measurement. This is assigned to the nanostructuring and to the Cr-depletion in the areas adjacent to the Cr-nitrides.

Surface integrity studies on abrasive water jet cutting of AISI D2 steel

ABSTRACTThis article investigates the 3D surface topography and 2D roughness profiles, and micrographs were analyzed in the abrasive water jet (AWJ) cutting of AISI D2 steel kerf wall cut surfaces by varying water jet pressures and jet impact angles. In 3D surface topography, roughness parameters such as Sq, Ssk, Sp, Sv, Sku, Sz, and Sa were improved by various jet impact angles with different water jet pressures. However, the roughness parameters Ssk and Sku strongly depend on the water jet pressure and jet impact angle. This is confirmed by kerf wall cut profile structures. Fine irregularities of peaks and valleys are found on the AWJ cut surfaces, as evident from 2D roughness profiles. The scanning electron microscope micrographs confirm the production of an upper zone not very much damaged and a lower striation free bottom zone, by using the jet impact angle of 70° with a water jet pressure of 200 MPa. Finally, the results indicate a jet impact angle of 70° maintaining the surface integrity of D2 steel better than normal jet impact angle of 90°. The results are useful in mating applications subjected to wear and friction. This has resulted in enhancement of the functionality of the AWJ machined D2 steel components.

High-temperature erosion of Fe-based coatings reinforced with cermet particles

High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbide–cobalt (WC–Co) and titanium carbide–nickel molybdenum (TiC–NiMo) cermet particles, are compared under high-temperature abrasive–erosive wear conditions. Both WC–Co and TiC–NiMo particles underwent fracture, as well as dissolution, during the spraying process, but in the case of WC–Co particles this process was remarkably less intensive. Under the low impact angle conditions, the WC–Co particle-reinforced coating exhibited 1.1 times lower wear than the TiC–NiMo particle-reinforced coating because of the larger amount of the reinforcement remaining. Under the normal impact angle conditions, the WC–Co particle-reinforced coating showed 1.2 times lower wear than the TiC–NiMo particle-reinforced coating because of the resulting larger size of the WC–Co reinforcement and a more ductile matrix.