Spray Welding Research Articles

Effect of N on microstructure, nucleation mechanism and mechanical performance of (Ti, Nb) C particles in Fe-based composite coating via plasma spray welding

Compared with the coating of Ti-Nb-C system, the coating of Ti-Nb-C-N system shows better mechanical properties, especially wear resistance. Therefore, this investigation was focus on the in-situ (Ti, Nb) C reinforced Fe-based composite coatings (D1 composite coatings) and in-situ (Ti, Nb) (C, N) reinforced Fe-based composite coatings (D2 composite coatings) which were created on high strength steel via plasma spray welding (PSW) technology in the environment with nitrogen and without nitrogen, respectively. The two coatings were compared to explore nucleation mechanism of nitrogen on (Ti, Nb) C particles, grain size, particle morphology and the influence on the mechanical performance of coatings. The findings showed that the changes in the typical microstructure morphology and the shape of the reinforced particles of the two coatings were not obvious. However, the heterogeneous nucleation sites of (Ti, Nb) C were provided by introducing nitrogen. In addition, the introduction of nitrogen could refine the grains of D1 composite coatings. As a result, the average grain size of D1 composite coatings decreased by an order of magnitude, and the crystal orientation of the grains in the composite coatings showed better isotropy. The average microhardness of D2 composite coatings was 967.52 HV1, which was 1.5 times of the average microhardness of D1 composite coatings. The wear loss of D2 composite coatings was 0.4 mg, which was only half of that of D1 composite coatings (0.8 mg).

Nucleation mechanism, particle shape and strengthening behavior of (Ti, Nb) (C, N) particles in Fe-based composite coatings by plasma spray welding

This study aimed to determine the nucleation mechanism, particle shape, and strengthening behavior of (Ti, Nb) (C, N) particles in Fe-based composite coatings. In this study, an in-situ technique combined with a plasma spray welding process was proposed to obtain a coating with in-situ (Ti, Nb) (C, N) particles. Composite coatings were successfully prepared on low-alloy steel by plasma spray welding using a mixture of Fe-based, Ti and Nb powders. N gas was used to provide the N atoms. The microstructural analysis results indicated that the reinforced particles transformed from irregular dendritic into massive and spherical particles, and then into spherical and lath particles, as the atomic ratio of Ti/Nb decreased. During solidification, TiN nucleated preferentially and Ti (C, N) particles were formed sequentially. Subsequently, NbC nucleated and grew with Ti (C, N) as its core, and (Ti, Nb) (C, N) particles were formed at the end. The microhardness values of these composite coatings were 680–970 HV, whereas that of low-alloy steel was 174 HV. The wear resistance of the composite coatings increased as the Ti/Nb atomic ratio decreased. The composite coating had the highest average microhardness and the best wear resistance when Ti/Nb = 1:3. Its average microhardness was five times more than that of the low-alloy steel. In addition, the mass loss of the composite coating was 0.4 mg, which is only one-sixth that of the low-alloy steel (2.4 mg). The main reason for this was the in-situ formation of (Ti, Nb) (C, N) particles, which were evenly distributed in the composite coatings.

Effect of Ti/Nb content on microstructure evolution and wear properties of in-situ (Ti,Nb)C reinforced composite coatings by plasma spray welding

Due to their superior wear resistance, multi-particle reinforced composite coatings have caught the interest of numerous researchers. In this research, a method of preparing composite coatings containing in-situ (Ti,Nb)C particles was proposed using plasma spray welding with a mixture of Fe-based alloy, pure Ti, and pure Nb powders. The research involved a detailed analysis of the nucleation mechanism, particle shape and strengthening behavior of (Ti,Nb)C particles in the composite coatings with different atomic ratio of Ti/Nb. The microstructure and phase were examined, and the wear resistance was tested and examined. The phase analysis results manifested that the composite coatings had primarily (Ti,Nb)C reinforcing phase and α-Fe matrix. The (Ti,Nb)C particles were not added in the raw powders, but in-situ generated via the reactions between the powders. The microstructure analysis results indicated that the reinforced particles transformed from irregular dendritic particles into lumpy and spherical particles, and then into an interspersed distribution of laths and spheres as the atomic ratio of Ti/Nb decreased. The microhardness value of these composite coatings when the Ti/Nb ratios were different were 550 HV–650 HV, while the microhardness value of the steel was 174 HV. However, with the increase of Ti/Nb atomic ratio, the change of wear resistance showed the trend: increase → decrease → increase. In-situ (Ti,Nb)C particles were uniformly distributed in the coatings and beneficial to improving the wear resistance. When Ti/Nb ratio is 1:1, the mass loss of the composite coating was only 0.6 mg, which was a quarter of the steel substrate (2.4 mg).

Effect of pool temperature on microstructure and corrosion resistance of PTAW Ni layer

In plasma transferred arc welding (PTAW), the weld pool temperature often fluctuates. The spray weld layer is prone to overheating, leading to adverse effect on its performance. This study investigated the influence of spray welding current on the weld pool temperature and in turn on the microstructure, microhardness and corrosion resistance of the PTAW-Ni layer on a steel substrate. Weld pool temperature increased with increasing spray welding current and varied along the welding gun path before reaching the steady state. With increasing pool temperature, more Fe diffused from the substrate into the spray weld layer, leading to a widened fusion zone, an increased dilution rate and a decreased microhardness. The spray weld layer has a dendritic microstructure. The dendrites have a higher Cr content, while the interdendritic regions have a higher Ni content. Increasing weld pool temperature increased diffusion, resulting in reduced enrichment of the Cr and Ni elements. The increase of Fe and decrease of Cr in the spray weld layer caused the decreasing corrosion resistance.

Study the Effect of Thermal Spraying With Various Ceramic Powders on The Sliding Wear of Steel Alloy( AISI1020 )

Aim of the study: This research studied the sliding wear resistance of the alloy (AISI 1020) after coating it with a thermal spraying process (NiAlCrSi) as a high-temperature binder, in addition to coating it with a thermal barrier consisting of aluminum oxide and magnesium oxide (Al2O3+MgO). With different weight concentrations of coating powders at the same temperature. With fixed time periods for both coatings. And make a comparison of the wear between the uncoated alloy and the coated alloy. Methods: A spray welding torch model (QH-2/H) was used to obtain ceramic coats. Sliding wear resistance was also conducted by a pin-on-disc arrangement device, which is designed as per ASTM D5963 specifications under the application of different vertical loads. SEM and XRD were used to analyze the coating's microstructure and phase composition. Results: The microstructure composition revealed the presence of several residues and primary phases, including Al2O3, Cr2O3, and CrNiO4, which are formed during the coating process, as well as secondary phases traceable back to nickel or chromium phases, in addition to other oxides such as CrMgO4. The morphological data further demonstrate that the coating was extremely heterogeneous, with a high oxide concentration, holes, and microfractures. Comparing the sliding wear results of different coated alloys with the base alloy revealed that there is a gradual increase in the wear rate of all tested samples with increasing loads applied to them. It was also found that the alloy (A4), which contains a large percentage of Al2O3, showed the lowest wear rate compared to the uncoated and coated base alloys. The wear rate of this alloy decreased by 64% under load (10 N) compared to the base alloy, while the coated sample (A3) showed higher wear rates than the uncoated base alloy, with an improvement percentage of 6%. Conclusions: Using the thermal spray method to paint alloys is economically feasible, in addition to saving time during coating, which does not exceed half a minute, and producing coatings with good mechanical resistance.

Research on microstructure and properties of 3D plasma spray welding repair layer of continuous casting segmented rollers

In this paper, the Fe-Cr-Ni-Si powder was used in a 3D plasma spray welding machine to perform spray welding repair tests on continuous casting segmented rollers for service life improvement. The phase composition, hardness distribution, abrasion resistance and thermal stability of the spray welding layer were analyzed. Results indicated that the spray welding layer produced by 160 A welding current was more uniform and was with finer organization. The main phase zone was a single γ-Fe and the fusion zone was metallurgically combined with the base metal in a planar grain manner. The hardness of the spray welding layer was the maximum when the welding current was 160 A. The abrasion resistance for each position of the spray welding layer was uniform. The γ-Fe phase zone decreased and the α-Fe phase zone increased with reduction of average hardness after the thermal stability test. In industrial tests, the optimum spray welding parameters were verified and the service life of the continuous casting segmented rollers with spray welding was 2 longer than rollers using surfacing welding process.

Solid-state cold spray welding: Evaluation and future direction

Welding is an important manufacturing process for joining complex parts. Despite their widespread use, there exist some drawbacks in the existing liquid-state (e.g., formation of undesirable heat-affected zones around weld area) and solid-state (e.g., high equipment and tooling costs, low production rates, and difficulty in joining intricate geometries) methods. These limitations continually spur the search for new joining processes to improve existing welding methods or develop new ones that circumvent these limitations. To provide a “greener” and low-cost alternative to the traditional welding processes that often produce “soft” heat affected zones (HAZs), we develop and evaluate the expansion of cold spray process—a solid-state high-velocity particle deposition process—to solid-state welding, a process we term cold spray welding (CSW). Using well-defined processing parameters, we cold spray welded (CSWed) AA 6061-T651 plate and compared the results with Tungsten inert gas (TIG) welded counterpart. Although TIG-welded samples exhibit higher tensile properties than CSWed samples (at least based on the CS processing parameters used in this study), our findings show that CSW indeed circumvents major drawbacks in traditional welding processes, including negligible microstructural alterations and the inhibition of deleterious phase transformation and suppression of deleterious HAZ. The examination of CSWed parts reveals low yield strength is connected to ubiquitous microvoids that are formed due to lack of metallurgical bonding; these microvoids act as microcrack initiation sites. We proceed to establish a failure mechanism in the CSWed part to provide direction for future optimization.

Study on corrosion behavior of 13Cr gate valve using weld deposited gate and seat in well operation environments

The different types of corrosion behavior occurred on a 13Cr gate valve using weld deposited gate and seat after about sixteen months of service in an oilfield in China, resulting in the leakage failure. In this study, the corrosion causes were investigated through visual inspection, mechanical performance testing, scanning electron microscopy, energy dispersive spectrometer and electrochemical analysis. The results demonstrated that the corrosion on the sealing surface of the valve body was related to the galvanic corrosion between the 304 SS ring gasket and 13Cr SS ring groove, which presented a significant potential difference in the spent acid environment. In addition, due to the C element diffusion from deposits during the spray weld on the surface of the gate and seat, a large amount of Cr enrich carbides were formed at the prior austenite grain boundaries in the 13Cr SS matrix side, which further induced the intergranular corrosion and cracking along the interface in service.

Fracture of Ni-Cr-Si-B thermal sprayed and fused reciprocating pump rods during straightening

A straightening fracture of an AISI 1045 pump rod with a fused coating by thermal spray welding was investigated. The fracture surface was surveyed for pinhole-related defects in the coating, debonding at the coating/substrate interface, and fracture initiation points. The base metal and coating were also examined using an optical microscope, scanning electron microscope with energy dispersive spectroscopy, tensile testing, and microhardness testing. The base metal rod experienced softening due to the thermal effect of spray welding and fusion. Large residual stress has been found in the outer coating layer using finite element analysis. The open-to-surface crack in the base metal was found to be partially filled by the hard coating. The brittle fracture is believed to be initiated at defects near the coating/rod interface and driven by a combined loading of thermal residual stresses and the applied straightening stress.

Microscopic Characteristics and Properties of Fe-Based Amorphous Alloy Compound Reinforced WC-Co-Based Coating via Plasma Spray Welding

Plasma spray welding, as one of the material surface strengthening techniques, has the advantages of low alloy material consumption, high mechanical properties and good coating compactness. Here, the Co alloy, WC and Fe-based amorphous alloy composite coating is prepared by the plasma spray welding method, and the coating characteristics are investigated. The results indicate that the coatings have a full metallurgical bond in the coating/substrate interface, and the powder composition influences the microstructures and properties of the coating. The hardness of coatings increases with the mass fraction of the Fe-based amorphous alloy. The spray welding layer has a much higher wear resistance compared with the carbon steel, and the Fe-20 exhibits a superior wear resistance when compared to others. The results indicate that the amorphous alloy powders are an effective additive to prepare the coating by plasma spray welding for improving the wear resistance of the coating.

Microstructure and Wear Behavior of In-Situ NbC Reinforced Composite Coatings.

In the present study, plasma spray welding was used to prepare an in-situ niobium carbide (NbC) reinforced Ni-based composite coating on the low carbon steel, and the phase composition and the microstructure of the composite coatings were studied. The wear resistance and the wear mechanism of the composite coatings were also researched by the wear tests. The results showed that the main phases of the composite coating were NbC, γ-Ni, Cr23C6, Ni3Si, CrB, Cr5B3, Cr7C3 and FeNi3. A number of fine in-situ NbC particles and numerous chromium carbide particles were distributed in the γ-Ni matrix. The increase in the mass fraction of Nb and NiCr-Cr3C2 could lead to the increase in NbC particles in the composite coatings. Due to the high hardness of NbC and chromium carbides, the micro-hardness and the wear resistance of the composite coatings were advanced. The composite coating with the powder mixtures of 20% (Nb + NiCr-Cr3C2) and 80% NiCrBSi had the highest micro-hardness and the best wear resistance in this study. The average micro-hardness reached the maximum value 1025HV0.5. The volume loss was 39.2 mm3, which was merely 37% of that of the NiCrBSi coating and 6% of that of the substrate under the identical conditions.

Effect of WC particles with different shapes during plasma spray on the properties of Fe-based composites coatings

The WC particles reinforced Fe-based spray welding layer was fabricated on the surface of 45 steel by plasma arc spray welding technology. The WC particles were irregular polyhedral and spherical, which were fed into the tail of the molten pool. The microstructure, phase composition, microhardness, and dry -sliding wear resistance of the coating were evaluated. The results show that the microstructure of the composite coating exhibits a hypoeutectic structure in addition to the WC, and the spherical WC particles are better preserved than the irregular polyhedral WC particles. The coating added with spherical WC particles has the best wear resistance, which is 1.28 times that of the coating added with irregular polyhedral WC particles.

Strengthening mechanism and properties of Co–WC composite coatings deposited by plasma‐transferred arc welding

Cobalt (Co)-based tungsten carbide (WC) wear-resistant coatings with different content of WC were prepared on the surface of Q235 low carbon steel by plasma-transferred arc welding. The properties of the coatings such as strengthening mechanism, microhardness and wear properties were tested by using a metallurgical microscope, scanning electron microscope, energy dispersive spectrometer, X-ray diffraction, Rockwell hardness tester, and friction wear equipment. The results show that the main reasons for the strengthening of spray welding layer are the solution strengthening formed by α-Co with supersaturated tungsten (W) and the dispersion strengthening caused by eutectic precipitated carbide and silicide. The proportion of the solid solution of W in α-Co steadily ranges from 18.00 to 19.59%. The morphologies of rich W-phase are mainly related to the content of W. With the content of W increasing, the evolution process of the shape is the amorphous form→damascene shape→star-like shape→the polygon. Amorphous W-rich phase can be obtained when the content of WC ranges from 20 to 30%, evenly distributed W-rich phase in the shape of damascene or star can be obtained when the WC content ranges from 30 to 40%, and the polygonal W-rich phase can be obtained at the percentage of 40-50%.

Microstructure and mechanical properties of Co-based alloy coatings fabricated by laser cladding and plasma arc spray welding

The presented paper concerned a comparison of microstructural characters and mechanical performances between the cobalt based alloy (Co-based) coatings of the same chemical composition and yet fabricated by laser cladding and plasma arc spray welding (PASW), respectively. The phase constituent and microstructure of the coatings was characterized by optical metallography, scanning electron microscopy (SEM), X-ray diffraction spectrum (XRD), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS), while the mechanical properties of the coatings obtained by different procedures were comparatively evaluated according to the microhardness and high-temperature wear resistance tests. As the novelties of the presented research, it was interesting that the amorphous Co-based coating was directly fabricated by laser cladding rather than by cladding-and-remelting method with commercial self-flux alloy powder for the first time. The formation mechanism of the amorphous phase was explained by experiments and finite element simulation. The advantages of the amorphous coatings in mechanical performances were quantitatively revealed.

Microscopic characteristics and properties of titaniferous compound reinforced nickel-based wear-resisting layer via in situ precipitation of plasma spray welding

TiC, TiB2 particles reinforced nickel-based composite wear-resistant layer can be generated by NiCrBSi, Ti and Si composite powder via plasma spray welding. Research has shown that composite powder spray welding layer mainly consisted of γ-Ni, FeNi3 and β1-Ni3Si matrix phases, as well as TiC, TiB2, CrB, M7C3, M23C6, SiC, TiSi2 and other hard phases inlaid in the matrix. Fine TiB2, TiC, M7C3, M23C6 and all SiC, CrB, TiSi2 are dispersed in the matrix, which can refine the sprayed-layer structure effectively. The grown TiB2 (6–50 µm) can be observed on the NiCrBSi+Ti+Si mixed powder spray-welding layer, TiB2 shows stepped growth through screw dislocation. The microhardness of NiCrBSi+Ti and NiCrBSi+Si spray-welding layer was lower than that of NiCrBSi+Ti+Si mixed powder spray-welding layer, and their abrasive resistance was 19 times and 26 times of that of H13 substrate respectively. When the content of added Ti and Si is 15%, the best properties of the NiCrBSi+Ti+Si mixed powder spray-welding layer are obtained with the microhardness reaching up to 980 HV0.5, which is approximately 2 times greater than that of the pure NiCrBSi spray-welding layer. Furthermore, its wearing capacity is merely 6.5 mg, so that the wear-resistance property is more than 5 times that of the pure NiCrBSi spray-welding layer, and even 50 times that of the H13 base material. However, the toughness of the spray-welding layers will be reduced, and even cracks that run through the entire spray-welding layer will be generated.

Repairing the surface grooves of St37 structural steel using flame spray welding

In today’s industry, preventive measures for the preservation and repair of devices and equipment are extremely important. Various welding methods are used for repairing the surface crack of metal pieces in order to improve their mechanical properties and increase their useful life. In the present study, the performance of flame spray welding using pure iron powder is evaluated in repairing the surface grooves of St37 structural steel. First, five groups of specimen (one control group and four grooved steel groups with 0.5 mm groove tip, 10 mm length and 0.5, 0.8, 1 and 1.3 mm groove depths) were prepared. Then, the repair was performed. The results showed that after repairing the surface groove via flame spray welding using pure iron powder, the tensile strength and yield strength of the repaired specimens with the groove depths of 0.5 and 0.8 mm were achieved to control ones, but the elongation was decreased, which was still acceptable for engineering applications (module of toughness of 74.2 MJ) for the repaired specimen with the groove depth of 0.5 mm.

Microstructures and Properties of Plasma Sprayed Ni Based Coatings Reinforced by TiN/C1-xNxTi Generated from In-Situ Solid-Gas Reaction.

The strengthening hard phases TiN/C1-xNxTi were generated by in-situ solid-gas reaction in Ni-based composite coatings prepared using a plasma spray welding process to reinforce the wear resistance of the coatings. The microstructures and properties of the coatings were investigated. The results showed that the coatings mainly consisted of phases such as TiN, C1-xNxTi, TiC, etc. A small amount of CrB, M7C3, and M23C6 were also detected in the coatings by micro-analysis method. Compared with the originally pure NiCrBSi coatings, the hardness of the NiCrBSi coatings reinforced by in-situ solid-gas reaction was 900 HV0.5, increased by more than 35%. Consequently, the wear resistance of the reinforced coatings was greatly improved due to the finely and uniformly dispersed hard phases mentioned above. The weight losses after wear test for the two kinds of coatings were 15 mg and 8 mg, respectively.

Repulsive Interaction of Sulfide Layers on Compressor Impeller Blades Remanufactured Through Plasma Spray Welding

This study investigated the repulsive interaction of sulfide layers on compressor impeller blades remanufactured through plasma spray welding (PSW). Sulfide layers on the blades made of FV(520)B steel were prepared through multifarious corrosion experiments, and PSW was utilized to remanufacture blade specimens. The specimens were evaluated through optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, 3D surface topography, x-ray diffraction, ImageJ software analysis, Vicker’s micro-hardness test and tensile tests. Results showed a large number of sulfide inclusions in the fusion zone generated by sulfide layers embodied into the molten pool during PSW. These sulfide inclusions seriously degraded the mechanical performance of the blades remanufactured through PSW.

Microstructures and Properties of NiCrBSi/WC Biomimetic Coatings Prepared by Plasma Spray Welding

The NiCrBSi/WC biomimetic coatings were prepared on the low carbon steel substrate by plasma spray welding with mixed powders (WC-Co12+NiCrBSi) based on the bionic principles, and the coating characteristics were investigated. The results indicate that the coatings have a full metallurgical bond in coating/substrate interface, and consist mainly of γ-Ni, WC, Cr23C6, Cr7C3, Ni3Si, Cr5B3, and FeNi3 phases. The powder composition influences the microstructures and properties of the coatings. The WC content and the hardness of coatings increase with the mass fraction of WC-Co12 powder. The biomimetic coatings have much higher wear resistance compared with the low carbon steel, which is attributed to the combination of hard WC and chromium carbide particles (bionic units) and soft γ-Ni matrix in the coatings. It is favorable to prepare the biomimetic coating by plasma spray welding with the mixed powders (20wt%WC-Co12+80wt%NiCrBSi) for improving the wear resistance of the coating.

Microstructures and properties of in-situ TiC particles reinforced Ni-based composite coatings prepared by plasma spray welding

In this investigation, the in-situ TiC particles reinforced Ni-based composite coatings were produced by plasma spray welding with mixed powders (NiCrBSi+Ti+NiCr–Cr3C2). Their microstructures and properties were studied. The experimental results showed that the composite coatings consisted mainly of γ-Ni, Cr23C6, Cr7C3, Ni3Si, Cr5B3, CrB, FeNi3 and TiC phases. TiC particles were in-situ synthesized during plasma spray welding. The content of TiC particles and chromium carbides in the coatings increased with the mass fractions of Ti and NiCr–Cr3C2 powders increasing in the mixed powders, which resulted in enhancing the composite coatings hardness. The composite coating prepared with the mixed powder (70wt%NiCrBSi+30wt% (Ti+NiCr–Cr3C2)) showed a higher hardness 1142HV0.5. The wear resistance of the composite coatings were greatly improved due to the presence of in-situ TiC particles in comparison with the substrate. When the mixed powder (75wt%NiCrBSi+25wt% (Ti+NiCr–Cr3C2)) was used, the composite coating had better wear resistance, and the coating wear volume loss after wear tests was 6mm3, which was only 5% of that for the low carbon steel substrate (125mm3).