Erosion Behavior Of Coatings Research Articles

Investigation of Single-Particle Erosion Behavior of Electroless Ni-P-Ti Composite Coatings

Electroless Ni-P-Ti composite coatings were deposited on AISI 1018 steel substrates by incorporating Ti nanoparticles into a Ni-P matrix. It was then followed by annealing to form the NiTi intermetallic precipitates within the coatings. In this study, single-particle erosion behavior of both as-deposited and annealed coatings was investigated. It was found that the erosion behavior of the coatings changes from a brittle (as-deposited) to a ductile erosion behavior (annealed) due to the formation of superelastic NiTi phase. Stress distribution during the single-particle impact process was calculated to facilitate the understanding of toughening and erosion mechanisms. Crack shielding and crack closing induced by transformation toughening were observed in the vicinity of the impact crater on the annealed 11.8 wt.% coating. This study discusses the erosion and toughening mechanisms of Ni-P-Ti composite coatings.

Single Particle Erosion Behavior of NiTi-Based Nanolaminates and Superelastic NiTi Monolayer Coatings

Bulk NiTi is used to make parts, such as couplings and bearings, that can be found in many industries such as the automotive, aerospace and medical sectors. Forming and machining bulk superelastic NiTi is a very difficult and costly process; however, applying NiTi as a surface coating will provide an alternate manufacturing method that will minimize machining processes. The objective of this study is to produce a superelastic NiTi-based surface coating that exhibits denting, impact and wear resistance. Superelastic NiTi has been successfully produced through vacuum deposition processes, despite this, there is a lack of a full and comprehensive study on the formation of the NiTi phase during coating development. In this study, the NiTi phase is fabricated through the annealing of sputtered deposited Ti and Ni layers in a coating. To confirm the presence of the intermetallic phases, X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analysis were performed. The erosion behavior of the coating is evaluated through single particle erosion testing, which resulted in the coatings that contained the NiTi precipitates to exhibit the best damage resistance compared to the other nanolaminates. This indicates that the superelastic NiTi phase increases the resistance to impacting particles. Microstructural evolution and NiTi formation during annealing is discussed and related to the observed damage resistance of the coatings.

Formation mechanism and supersonic flame erosion behavior of SiC and SiC-SiCnano single-layer oxidation protective coatings for carbon materials by reactive melt infiltration (RMI) method

In this study, chemical and mechanical erosion mechanism of SiC single-layer coatings were evaluated using supersonic flame erosion test, X-ray diffraction, and scanning electron microscopy. In the first step, the formation mechanism of SiC coating on graphite substrate was investigated by HSC Chemistry software version 6.0 and then the effects of infiltration temperature and SiC nanoparticles addition on erosion behavior of the coatings were studied. The results of erosion test under supersonic flame at a 90° angle after 120 s indicated that chemical and mechanical erosion occur simultaneously during erosion test but mechanical erosion is the dominant mechanism which causes to sample destruction. However, with SiC nanoparticles addition and increasing the infiltration temperature, mechanical erosion decreased. By increasing of infiltration temperature, mass erosion rate and linear erosion rate decreased from 2.52 × 10−3 g cm−2 s−1 and 32.7 μm s−1 to 1.09 × 10−3 g cm−2 s−1 and 3.33 μm s−1 respectively. Also, with addition of SiC nanoparticles, mass and linear erosion rate decreased from 2.52 × 10−3 g cm−2 s−1 and 32.7 μm s−1 to 1.04 × 10−3 g cm−2 s−1 and 2.17 μm s−1 respectively.

Slurry erosion performance study of HVFS sprayed Ni-20Al2O3 and Ni-15Al2O3-5TiO2 coatings under hydro accelerated conditions

PurposeThis paper aims to cover all the aspects of development, investigation and analysis phases to evaluate the slurry erosion performance of test coatings. The powders having composition of Ni-20Al2O3 and Ni-15Al2O3-5TiO2 were deposited on CA6NM grade turbine steel by using high velocity flame spray (HVFS) technique. The characterization of the coatings was done with the help of SEM/EDS and XRD techniques. Various properties such as micro-hardness and bonding strength of the coatings were also evaluated. Thereafter, these coatings were subjected to an indigenously developed high speed slurry erosion tester at different levels of rotational speed, erodent particle size and slurry concentration. The effect of these parameters on the erosion behavior of coatings was also evaluated. The slurry erosion tests and SEM of the eroded surfaces revealed remarkable improvement in slurry erosion resistance of Ni-15Al2O3-5TiO2 coating in comparison with Ni-20Al2O3 coating.Design/methodology/approachTwo different compositions of HVFS coating were developed onto CA6NM steel. Subsequently, these coatings were evaluated by means of mechanical and microstructural characterization. Further, slurry erosion testing was done to analyze the erosive wear behavior of developed coatings.FindingsThe coatings were successfully developed by HVFS process. Cross-sectional microscopic analysis of sprayed coatings revealed a continuous and defect-free contact between substrate and coating. Ni-15Al2O3-5TiO2 coating showed higher value of bond strength in comparison with Ni-20Al2O3 coating. Under all the testing conditions, Ni-15Al2O3-5TiO2 coatings showed higher resistance to slurry erosion in comparison with Ni-20Al2O3 coatings. Rotational speed, average particle size of erodent and slurry concentration were found to have proportional effect on specific mass loss of coatings. The mixed behavior (brittle as well as ductile) of the material removal mechanism was observed for the coatings.Originality/valueFrom the literature review, it was found that researchers have documented the various studies on Ni-Al2O3, Ni-TiO2 and Al2O3-TiO2 coatings. No one has ascertained the synergetic effect of Alumina and Titania on the slurry erosion performance of Nickel-based coating. In view of this, the authors have developed Ni-Al2O3 and Ni-Al2O3-TiO2 coatings, and an attempt has been made to compare their mechanical, microstructural and slurry erosion characteristics.

Slurry Erosion Performance of Ni-Al2O3 Based Thermal-Sprayed Coatings: Effect of Angle of Impingement

In this paper, slurry erosion performance of high velocity flame-sprayed Ni-Al2O3 based coatings was evaluated. The coatings were deposited on a hydroturbine steel (CA6NM) by varying the content of Al2O3 in Ni. Using jet-type test rig, erosion behavior of coatings and bare steel was evaluated at different impingement angles. Detailed investigation of the surface morphology of the eroded specimens was undertaken using SEM/EDS to identify potential erosion mechanism. A parameter named “erosion mechanism identifier” (ξ) was used to predict the mode of erosion. It was observed that the coating prepared using 40 wt.% of Al2O3 showed a highest resistance to erosion. This coating enhanced the erosion resistance of the steel by 2 to 4 times. Spalling in the form of splats and chunks of material (formed by interlinking of cracks) along with fracture of Al2O3 splats were identified as primary mechanisms responsible for the loss of coating material. The erosion mechanism of coatings and bare steel predicted by ξ was in good agreement with that observed experimentally. Among different parameters,\( \left( {K_{\text{IC}}^{2} H} \right)^{1/3} \), a function of fracture toughness (KIC) and hardness (H) showed excellent correlation with erosion resistance of coatings at both the impingement angles.

A study on erosive wear behavior of HVOF sprayed nanostructured WC-CoCr coatings

WC-CoCr cermet coatings were deposited on stainless steel substrate using high-velocity oxy-fuel (HVOF) thermal spray process. The coatings were developed with two different thermal spray powders: one has WC grains of conventional micron size and the other is composed of nanosized (near-nanostructured) grains. HVOF spraying was assisted with in-flight particle temperature and velocity measurement system to control the process parameters that have resulted in quality coatings. Cavitation erosion testing was performed using a vibratory test apparatus based on ASTM standard G32-98. Surface morphology of powders and coatings was examined using the FESEM images, and phase identification was performed by XRD analysis. The erosion behavior of coatings and mechanism of material removal was discussed by examining the microstructure images of worn-out surfaces. WC-CoCr cermet coating deposited with nanosized WC grains exhibited higher cavitation erosion resistance as compared to conventional coating.