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Inconel 718 is extensively used in various industrial applications; however, its susceptibility to corrosion in aggressive environments remains a significant concern. In this study, Stellite 6, a cobalt-based alloy known for its excellent wear and corrosion resistance, was deposited onto Inconel 718 using the plasma spray coating technique. The coated material is characterized through SEM and EDS. Through SEM surface morphology, coating uniformity, and microstructural features are investigated. To evaluate corrosion behavior, potentiodynamic polarization tests were conducted in chloride-rich environments, namely 3.5 wt% NaCl and 1 M HCl solution, simulating extreme industrial conditions. Electrochemical evaluations demonstrated a marked improvement in the corrosion resistance of the substrate following Stellite 6 coating, relative to the uncoated material. The superior performance of the coating is based on its dense microstructure and chemical stability, acting as a good barrier against corrosive media, minimizing localized attack, and reducing material degradation. The results indicate that plasma-sprayed Stellite 6 coatings could be an excellent solution for increasing the life of Inconel parts in corrosive service environments.

In this study, a novel mixed stellite coating made from the 30% Stellite 3 and 70% Stellite 21 is deposited on H13 alloy using laser cladding technology, aiming at improving the micro-hardness and wear properties compared to Stellite 21. The microstructures of the mixed Stellite coating and Stellite 21 coating are examined using optical microscopy, scanning electron microscopy, and energy-dispersive spectrometer. The wear resistance of both Stellite coatings is evaluated by dry sliding wear test method. The results demonstrate that the Stellite 21 coating is composed of γ-Co, Co 3 Mo interdendritic phase and M 23 C 6 carbide, while the mixed Stellite coating is only composed of γ-Co and M 7 C 3 carbide-enriched W and Mo. The mixed Stellite coating exhibits superior micro-hardness and wear properties compared to the Stellite 21 coating.

Laser metal deposition (LMD) is one of the manufacturing processes in the industries, which is used to enhance the properties of components besides producing and repairing important engineering components. In this study, Stellite 6 was deposited on precipitation-hardened martensitic stainless steel (17-4 PH) by using the LMD process, which employed a pulsed Nd:YAG laser. To realize a favor deposited sample, the effects of three LMD parameters (focal length, scanning speed, and frequency) were investigated, as well as microstructure studies and the results of a microhardness test. Some cracks were observed in the deposited layers with a low scanning speed, which were eliminated by an augment of the scanning speed. Furthermore, some defects were found in the deposited layers with a high scanning speed and a low frequency, which can be related to the insufficient laser energy density and a low overlapping factor. Moreover, various morphologies were observed within the microstructure of the samples, which can be attributed to the differences in the stability criterion and cooling rate across the layer. In the long run, a defect-free sample (S-120-5.5-25) possessing suitable geometrical attributes (wetting angle of 57° and dilution of 25.1%) and a better microhardness property at the surface (≈335 Hv) has been introduced as a desirable LMDed sample.

The effectiveness of a machining process can be determined by analysing the quality of the generated surface and the rate of tool wear. Stellite is highly challenging to machine, which is why it is primarily processed through grinding methods. This study concentrates on the impact of cutting parameters and tool wear (VBb, KBb) on the created surface roughness surface (Rt, Ra, Rz) during the orthogonal cutting of Stellite 6, which is overlaid on a steel surface, C45, prepared by means of HP/HVOF (JP-5000). The results indicate that the dominant influence on the change in the total roughness profile height value (Rt) is the mutual interaction of cutting speed and depth of cut at 16% (p < 0.000). The greatest impact on the change in the mean arithmetic deviation of the roughness profile (Ra) value is the interaction of cutting speed, tool front angle, and depth of cut with a 15% share (p < 0.000), as well as on the change in the Rz value (15%) and tool wear VBb (25%). This investigation lays the groundwork for potentially substituting the processing of flat surfaces with hardened layers created by thermal spraying (such as Stellite 6) with grinding or methods that offer greater efficiency from both economic and technological perspectives.

Stellite 6 is a cobalt-based superalloy which has a good wear and corrosion resistance and retains these properties at high temperatures. In this study, wire and arc additive manufacturing (WAAM based on the GMAW) was employed to deposit Stellite 6 wire on low alloy high strength steel (S355) and stainless steel (AISI 420) plates. One of the main interests of this study is to produce WAAM Stellite 6 deposits with quality comparable with laser deposition. The advantages of the WAAM process include the high deposition rate, high productivity, high material usage, and energy efficiency with low cost. However, superalloy deposition generally requires maintaining a low dilution level to avoid jeopardizing the integrity of the deposit. As a result, it is important to manage the excess heat input during the WAAM deposition process through a parametric optimization of WAAM deposition of Stellite 6 on S355 steel substrates. In this study, a WAAM process window is established to guide the process optimization. The optimization method used in this study has been applied in our previous laser cladding work. The generated process window also shows some correlations among the heat input, bead geometry, and dilution. The effects of heat input on the resulting microstructure, elemental distribution, and hardness were discussed. Dilution, microstructure, and hardness were considered for comparison from previous studies of laser cladding deposits. In addition, the obtained optimal conditions were adapted to apply WAAM deposition of Stellite 6 layers on AISI 420 stainless steel substrates. The XRD result shows that WAAM deposits contain Co-Cr-Fe solid solution (FCC), Cr 7 C 3 and Cr 3 C 2 carbides, and Co 4 W 2 C intermetallic compound. The results obtained through this study lay a foundation for future research on the wear properties of WAAM Stellite 6 deposits. This can contribute to further development of automated deposition of Stellite 6 using WAAM process for industrial applications.

This paper investigates the effect of plasticity ball burnishing on characteristics of surface integrity, residual stress and hardness of laser direct energy deposited (DEDed) Stellite 21 alloys, with a focus on the burnishing directional effect on surface and microstructural deformation. The results demonstrated that the burnishing improved surface finish, reducing Sa and Sz by 24% and 47%, respectively. The burnishing flattened and modified the cellular/columnar grains at a depth of 50 µm, with the most notable changes observed on the cross-sectional plane normal to the burnishing direction. Compared to the ground surface, the burnishing introduced higher and deeper compressive stresses along normal to the burnishing/grinding direction (−1341 MPa and 61 µm) as compared to that along the burnishing direction (−449 MPa and 56 µm). Likewise, the burnishing increased the full width at half maximum (FWHM) in the same fashion by broadening XRD peaks along normal to the burnishing direction. Due to higher grain modification and dislocation density, the burnishing has improved microhardness at a depth of 320 µm by 26% along normal to the burnishing direction. These findings demonstrate that the plasticity ball burnishing has a directional effect on plastic deformation and can be considered a plausible technique for tailored surface integrity, residual stress and hardness, which potentially improve the service performance of DEDed Stellite 21 alloy components.

From the wide range of engineering materials traditional Stellite 6 (cobalt alloy) exhibits excellent resistance to cavitation erosion (CE). Nonetheless, the influence of ion implantation of cobalt alloys on the CE behaviour has not been completely clarified by the literature. Thus, this work investigates the effect of nitrogen ion implantation (NII) of HIPed Stellite 6 on the improvement of resistance to CE. Finally, the cobalt-rich matrix phase transformations due to both NII and cavitation load were studied. The CE resistance of stellites ion-implanted by 120 keV N+ ions two fluences: 5 × 1016 cm−2 and 1 × 1017 cm−2 were comparatively analysed with the unimplanted stellite and AISI 304 stainless steel. CE tests were conducted according to ASTM G32 with stationary specimen method. Erosion rate curves and mean depth of erosion confirm that the nitrogen-implanted HIPed Stellite 6 two times exceeds the resistance to CE than unimplanted stellite, and has almost ten times higher CE reference than stainless steel. The X-ray diffraction (XRD) confirms that NII of HIPed Stellite 6 favours transformation of the ε(hcp) to γ(fcc) structure. Unimplanted stellite ε-rich matrix is less prone to plastic deformation than γ and consequently, increase of γ phase effectively holds carbides in cobalt matrix and prevents Cr7C3 debonding. This phenomenon elongates three times the CE incubation stage, slows erosion rate and mitigates the material loss. Metastable γ structure formed by ion implantation consumes the cavitation load for work-hardening and γ → ε martensitic transformation. In further CE stages, phases transform as for unimplanted alloy namely, the cavitation-inducted recovery process, removal of strain, dislocations resulting in increase of γ phase. The CE mechanism was investigated using a surface profilometer, atomic force microscopy, SEM-EDS and XRD. HIPed Stellite 6 wear behaviour relies on the plastic deformation of cobalt matrix, starting at Cr7C3/matrix interfaces. Once the Cr7C3 particles lose from the matrix restrain, they debond from matrix and are removed from the material. Carbides detachment creates cavitation pits which initiate cracks propagation through cobalt matrix, that leads to loss of matrix phase and as a result the CE proceeds with a detachment of massive chunk of materials.

The article presents research results on the possibility of shaping the structure and properties of Co-Cr-W-C-Ti alloys (type Stellite 6) using laser cladding technology. Cobalt-based alloys are used in several industries because they are characterized by high erosion, abrasion, and corrosion resistance, retaining these properties at high temperatures. To further increase erosion resistance, it seems appropriate to reinforce material by in situ synthesis of hard phases. Among the transition metal carbides (TMCs), titanium carbide is one of the hardest and can have a positive effect on the extension of the lifetime of components made from cobalt-based alloys. In this article, concentration of C, W, and Ti due to the possibility of in situ synthesis of titanium carbides was subjected to detailed analysis. The provided research includes macrostructure and microstructure analysis, X-ray diffraction (XRD), microhardness, and penetrant tests. It was found that the optimal concentrations of Ti and C in the Co-Cr-W-C alloy allow the formation of titanium carbides, which significantly improves erosion resistance for low impact angles. Depending on the concentrations of titanium, carbon, and tungsten in the molten metal pool, it is possible to shape the alloy structure by influencing to morphology and size of the reinforcing phase in the form of the complex carbide (Ti,W)C.

To address the issue of cracking in aluminum extrusion dies during operation, this study employs laser cladding technology to modify the surface of these dies. This modification aims to enhance their hardness and friction resistance. Laser cladding technology was utilized to coat the surface of H13 steel with Stellite 12, a cobalt-based alloy, at varying laser power levels. The surface formation quality, microstructural organization, phase composition, microhardness, and wear resistance of the coatings were investigated using optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction (XRD), microhardness testing, and confocal microscopy. The results indicated that as the laser power increased, the surface formation quality of the coating gradually improved, while the dilution rate of the coating increased. Changes in the phase composition and microstructure were not significant, and both microhardness and wear resistance initially increased before decreasing. Optimal process parameters for achieving good surface formation quality, high microhardness, and strong wear resistance were found to be a laser output power of 2200 W, scanning speed of 10 mm/s, feeding rate of 1.2 r/min, and overlap rate of 40%. The results indicate that the coating applied to the surface of H13 steel using Stellite 12 enhances the performance of aluminum extrusion dies.

In the present study, the Stellite 12 coating was prepared on 304 stainless steel using laser cladding technology. The phase composition, microstructure, and friction behavior of the cladding layer under the four loads were analyzed. The results showed severe lattice distortion in the coating. As the temperature gradient and solidification rate were diverse in each region, the upper, middle, and lower sections of the coating layer exhibited various microstructure morphologies. The intergranular part of the cladding layer was mainly the eutectic structure, and the inner crystal was mainly Co solid solution. Spalling and adhesive phenomena appeared at the bottom of the specimen when the action was under a load of 90 N and 150 N. The average wear of the cladding layer improved with the increase in load, the shear stress and temperature in the contact zone were enhanced distinctly, and the specimen became more prone to plastic deformation and wear intensification.