As a breakthrough of the additive manufacturing technology being achieved, many fields have broadly applied laser cladding due to its unique advantages. But the surface characteristics of the cladding layer are not frequently aligned with the standards necessary for industrial use. Consequently, with a particular focus on refining its surface roughness, it has emerged as a significant area of interest among numerous investigators. This paper reviews a variety of methods for optimizing the surface roughness of laser cladding, covering from deterministic algorithms such as Taguchi's method, orthogonal experimental method, gradient descent method, to stochastic algorithms including neural network, genetic algorithm, Gray Wolf algorithm, and even hybrid algorithms combining multiple algorithms like neural network genetic algorithm, adaptive neural fuzzy reasoning algorithm, and improved genetic algorithms for response surface analysis, and so on. Through comparative analysis, it is found that the hybrid algorithms can quickly generate the optimal optimization parameters for the sake of achieving the optimal surface quality since they may combine the accuracy of deterministic algorithms and the robustness of stochastic algorithms. In addition, this paper also looks forward to the future development direction of surface quality optimization methods for laser cladding, aiming at laying a foundation for the research work of high-quality coating preparation.

The determination of eigenstrain from residual stress is a crucial aspect in process predicting and optimizing of laser peen forming. However, direct measurement of eigenstrain is not possible, and therefore an indirect method based on the Fredholm integral equation is proposed for determining eigenstrain from residual stress. The residual stress of full-coverage laser shock peening (LSP) is analyzed, and the governing equation of eigenstrain is derived from the elastic deformation of a linear elastic plate under full-coverage LSP. The governing equation is a second-kind Fredholm integral equation, which can be solved analytically using the weight function method. Since residual stress is difficult to measure accurately in LSP, an inverse method based on the integral governing equation is proposed for determining eigenstrain from an incomplete set of measurements. The validity of this method is demonstrated through simulation and experimental results, highlighting its high efficiency and engineering application value.

Aseptic loosening and inadequate osseointegration are significant issues associated with titanium alloy implants in complex body fluid environments. Surface coatings techniques are often employed to enhance the bioactivity and osseointegration capabilities. In this research, biocomposite coatings were fabricated on Ti-6Al-4V alloy employing micro-arc oxidation (MAO) and the integration of micro-arc oxidation/electrophoretic deposition (MAO/EPD) technology. Microstructure, bioactivity, and corrosion resistance of the coatings were studied. To investigate the effect of the coatings on the stress corrosion cracking (SCC) behavior of Ti-6Al-4V alloy, slow strain rate tension (SSRT) tests were conducted in simulated body fluid (SBF). Results show that the adhesive strength of the MAO/EPD composite coatings is around 28.41N, with an average contact angle of 19.05 °, indicating excellent wettability and biocompatibility. The corrosion rate of biocomposite coatings is 3.43 μm·a −1 and the biocomposite coatings exhibit excellent SCC resistance, with a SCC sensitivity of 9.21%, which is significantly lower than the 18.39% of Ti-6Al-4V alloy. This can be attributed to the lower porosity of the coatings, which can provide excellent protection for the alloy.

The temperature of the zinc bath and the immersion duration are critical factors that significantly impact the surface quality and adhesion of batch hot-dip galvanizing coatings. This study focuses on the influence of different zinc bath temperatures (460, 490, and 520 °C) and immersion duration (1, 3, 5, and 10 min) on the hot-dip galvanized coatings of Fe-Mn-Al-C lightweight steel, which were characterized using scanning electron microscopy and energy dispersive X-ray analysis. The results demonstrate that with the increasing zinc bath temperature and immersion duration, the coating thickness and bond strength initially increase and then decrease. The inhibition layer in the coating gradually fractures and thickens with the rising temperature, leading to changes in the alloy phases within the coating. The optimal batch hot-dip galvanizing condition for the experimental steel is immersing at 490 °C for 3 min. Furthermore, we conducted a neutral salt spray corrosion test on the specimens under the optimal batch hot-dip galvanizing condition to study their corrosion behavior and mechanism and evaluate the impact of batch hot-dip galvanizing on the corrosion resistance of Fe-Mn-Al-C steel.

Scale deposition on the surface of pipelines is a common phenomenon in industrial production. It not only decreases the heat conduction efficiency of the pipeline and increases energy consumption, but also leads to corrosion of the pipeline. Although varieties methods are developed to prevent pipeline scale deposition, these methods could not meet the requirements of harsh production conditions. This study introduces a novel oil-infused surface on galvanized iron for efficient anti-scaling in industrial pipelines. The surface of galvanized iron is firstly oxidized and modified to be superhydrophobic/superoleophilic, followed by injection of oil to form oil-infused surface. This oil-infused superhydrophobic/superoleophilic surface demonstrates excellent water repellency and superior anti-scaling performance compared to untreated galvanized iron. It may provide a promising anti-scaling option for iron-based pipelines in industrial productions.

To enhance anti-corrosion property of AZ31 magnesium alloys, slippery liquid-infused porous surfaces (SLIPSs) were prepared on benzoate-intercalated Mg-Al layered double hydroxides (LDHs). The typical morphology of SLIPSs was determined using a scanning electron microscope, and the successful loading of benzoate ions was confirmed by an X-ray diffractometer (XRD). Especially, this work focused on revealing how hydrothermal time affected the resistance to corrosion of SLIPSs. The electrochemical results indicated that when the hydrothermal duration was 24 h, the developed SLIPS exhibited remarkably improved corrosion resistance accompanied by the lowest corrosion current density of 2.5 × 10−3 μA cm−2. Furthermore, the results of immersion test demonstrated the superiority of SLIPSs in anti-corrosion durability. Based on the obtained results, the prepared SLIPSs can be promising candidates for the improvement in anti-corrosion performance of magnesium alloys.

Thermal spray coatings enhance one or more surface properties of engineering components. In this work, NiCrSiBCFe-WC-Co composite coating powder is deposited over SA213-T12 boiler steel using the high velocity oxy fuel spraying (HVOF) and low velocity oxy fuel spraying (LVOF) thermal spray methods to improve erosion performance. XRD and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) were used to examine the surfaces and constituents of as-deposited specimens, whereas SEM was used to investigate the eroded specimens. The erosion behaviours of developed coatings were investigated at 30° and 90° impact angles, 53 m/s and 400°C. XRD analysis of the HVOF coating showed an additional peaks of NiCo2O4, SiC and Ni2B with common peaks Ni, WC, W2C, Cr23C6 and C6(Cr,Co,Ni)23 to that of LVOF coating. HVOF-sprayed coating demonstrated higher microhardness and adhesion strength with lower porosity than LVOF-sprayed coating. The HVOF-sprayed NiCrSiBCFe-WC-Co coating demonstrated comparatively better erosion resistance than LVOF-sprayed NiCrSiBCFe-WC-Co coating, attributed to its superior properties. The mechanism of erosion, concerning the different characteristics of the coatings, is discussed.

This study is aimed at fabricating composite biocompatible coatings of Alginate (Alg) and Chitosan (CS) on a stainless steel (grade 316L) substrate, reinforced with several percent nanoparticle additives, Using a dip coating method. The research used Fourier Transform Infrared (FTIR), field emission scanning electron microscopy (FESEM), and Atomic force microscopy (AFM) to explore surface roughness, size dispersion, and surface topography. The introduction of nanoparticles enhanced the wettability of the CS/Alg coatings. Notably, nanoparticle coatings with TiO2, Nb2O5, and biotin showed exceptional wettability due to the hydrophilic qualities of the matrix and reinforcements. This was corroborated by contact angle measurements, which confirmed the hydrophilic nature of the chitosan-alginate blend. The FTIR results highlighted the noticeable compatibility between CS-Alg and (TiO2, Nb2O5, and biotin) nanoparticles. No discernible alterations in the wavelengths were observed. Employing biotin-TiO2-Nb2O5, the FESEM showed that the biocompatible coating films were uniform and devoid of cracks on the 316L stainless steel substrate. The matrix + TiO2, matrix + Nb2O5, matrix + TiO2 + Nb2O5, and matrix + TiO2 + Nb2O5 + biotin-coated 316L stainless steel showed roughness data of 4.14, 5.28, 7.04, and 8.02 nm, accordingly, in contrast with the neat chitosan/alginate coating, which displays 2.67 nm, suggesting the significant impact of biotin and oxides on surface topography. These findings underscore the potential of the developed nanoparticle coatings for orthopedic applications, with enhanced wettability and biocompatibility. Biocompatible coatings emerging from this research are promising for advancing orthopedic and biomedical devices as they are used in scientific studies because of their biocompatibility with human tissues.

To make Mg alloy implants have better corrosion resistance and reduced degradation rate in the human body, hydroxyapatite (HA), polypropylene (PP), and HA+PP coatings were added to the surface of AZ31B through dip coating. Coated samples were tested for weight differences, corrosion rate, surface roughness, and microscopic view. Scanning electron microscopy and energy dispersive spectroscopy analysis confirm coating on the substrate surfaces. The potentiodynamic polarisation test result shows that the corrosion rate in the uncoated substrate (10.138 mm/y) was higher compared to HA-coated = 0.5084 mm/y, PP-coated = 0.442 mm/y, and HA/PP-coated = 0.3275 mm/y. After 14 days, weight loss (5.5%) was highest in the uncoated and lowest in the HA-PP-coated (0.9%). Deposition of the bone mineral was higher on the HA-coated sample, showing superior bone integration properties. Hybrid coating improved electrochemical properties compared to HA coating on Mg alloy.