Plasma Transferred Arc Cladding Process Research Articles

Investigation on wear behaviour of TiC/Co/Y2O3 metal matrix composite coating developed on AZ91D Mg alloy by plasma transferred arc cladding process

A high wear resistant TiC/Co/Y2O3 composite coating was synthesized on the surface of AZ91D Mg alloy by plasma transferred arc (PTA) coating process. The results showed that the major phases present in the coating were TiC, Al2O3, Y2C3, Y2Al, TiCo3 and Co2Ti. The coatings had a sound metallurgical bonding to AZ91 Mg alloy substrate. The maximum average surface hardness of TiC/Co/Y2O3 composite coated layer was found to be around 3374 HV0.05, which is about 49 times higher than that of AZ91D Mg alloy (68 HV0.05). The wear rate of the coatings was 8.48 × 10-8 g/N-m, which was reduced about seven times as compared to AZ91D Mg (58 × 10-8 g/N-m). It was concluded that the wear resistance of TiC/Co/Y2O3 composite coating was enhanced as compare to the AZ91D Mg alloy. This type of TiC/Co/Y2O3 coating may increase the application of AZ91D Mg alloy in the automotive industries for manufacturing of tribological components.

A New Design of In Situ Ti(C,N) Reinforced Composite Coatings and Their Microstructures, Interfaces, and Wear Resistances.

Here, a unique combination of a novel carbon-nitrogen source (g-C3N4) with different mole ratios of Ti/g-C3N4 has been utilized to fabricate iron matrix composite coatings by a synchronized powder feeding plasma transferred arc (PTA) cladding technology. The results show that submicron Ti(C,N) particles are successfully fabricated in situ on a Q235 low carbon steel substrate to reinforce the iron matrix composite coatings and exhibit dense microstructures and good metallurgical bonding between the coating and the substrate. The microstructure of the coating consists of an α-Fe matrix and Ti(C,N) particles when the mole ratio of Ti/g-C3N4 is no more than 5:1. The microhardness and wear resistance of the coating gradually improve with increasing abundance of the in-situ-synthesized Ti(C,N) particles. Interestingly, for a Ti/g-C3N4 mole ratio of 6:1, a fine lamellar eutectic Laves phase (Fe2Ti) appears, and this phase further improves the microhardness and wear resistance of the coating. The microhardness of the coating is 3.5 times greater than that of the Q235 substrate, and the wear resistance is enhanced 7.66 times over that of the substrate. The Ti(C,N)/Fe2Ti and Fe2Ti/α-Fe interfaces are very clean, and the crystallographic orientation relationships between the phases are analyzed by high-resolution transmission electron microscopy (HRTEM) and an edge-to-edge matching model. The theoretical predictions and the experimental results are in good agreement. Furthermore, based on the present study, for the solidification process near equilibrium, smaller interatomic spacing misfits and interplanar spacing d-value mismatches contribute to the formation of crystallographic orientation relationships between phases during the PTA cladding process. The existence of orientation relationships is beneficial for improving the properties of the coatings. This work not only expands the application fields of g-C3N4 but also provides a new idea for the preparation of Ti(C,N) particle-reinforced composite coatings.

Synthesis of Fe-based coatings by low frequency electromagnetic stirring: Evolution of microstructure and mechanical properties

Abstract The effects of low frequency electromagnetic stirring (EMS) on the microstructure and mechanical properties of the Fe-Cr-C alloys coatings prepared by plasma transferred arc cladding process have been investigated. The results showed that the microstructure of the coatings consists of primary (Fe, Cr)7C3 and austenite plus (Fe, Cr)7C3 eutectics. At a lower stirring frequency (0 to 10 Hz), the morphologies of (Fe, Cr)7C3 carbides change from blade-like to hexagon-like shape at first, while it promotes nodular-like (Fe, Cr)7C3 carbides formation at higher frequency (15 to 20 Hz). The high volume fraction (78.2%) and the most refined crystalline (31 μm) of hexagon-like (Fe, Cr)7C3 carbides are obtained under the optimum EMS at 10 Hz. It is also corresponding variations in mechanical properties with structural evolutions. For the coating without EMS, the average hardness (H) and fracture toughness (KIC) are 798 Hv100 and 2.86 MPa m1/2, respectively. These properties are remarkably improved as function of stirring frequency (H = 1164 Hv100 and KIC = 4.28 MPa m1/2 are achieved in the coating with EMS at 10 Hz). But further increase of stirring frequency, it induces the decrease of H and KIC. The different microstructural characteristics and distribution morphologies responsible for these EMS-induced changes in mechanical properties and wear resistance of the coatings are discussed in details.

Microstructure and wear behaviour of plasma transferred arc (PTA)-deposited FeCrC composite coatings on AISI 5115 steel

Plasma transferred arc (PTA) cladding was used to produce composite coatings on the surface of AISI 5115 steel using five different energy inputs and ferrochromium (FeCrC) powder. The effects of different energy inputs and of ferrochromium powder on the microstructure, hardness, and wear behaviour were investigated. The dry-sliding wear properties of the samples were determined using the ball-on-disk wear test method. The alloyed surfaces exhibited increases in hardness and wear resistance and a decrease in the coefficient of friction. The increase in hardness was explained by the presence of hard phases, such as the martensitic phase, Cr7C3, C3Cr7, Fe23C6 and iron carbides, in the microstructure. The average coefficient of friction value of the substrate was determined to be 0.83, whereas these values for the composite layers varied between 0.62 and 0.73. The lowest wear rate (2.88×10−6mm3/N/m) was observed for the 100A PTA cladding sample. The industrial coating process was applied to an AISI 5115 steel rolling cylinder using the optimum parameters (100A), which were determined after experimental studies. The PTA cladding process on the rolling cylinder improved the useful life by approximately 2.5-fold compared to the actual rolling cylinder.

Evolution of microstructure and mechanical properties of in situ synthesized TiC–TiB2/CoCrCuFeNi high entropy alloy coatings

The aim of this paper was to explore a one-step in situ method to synthesize the TiC–TiB2 reinforced CoCrCuFeNi high entropy alloy composite coatings. In this method, the composite coatings were prepared by plasma transferred arc cladding process using Ti, B4C, Co, Cr, Cu, Fe, and Ni powder mixture as precursors. The effects of CoCrCuFeNi(Ti, B4C)x (x in molar ratio, 0.1≤x≤0.5) additions on the structure and mechanical properties of the coatings were investigated. For 0.1≤x≤0.2, the coatings induce the formation of face-centered cubic (FCC) and body-centered cubic (BCC) plus TiC structures. Further addition of x content (0.3≤x≤0.5), promotes high volume fraction of dual-phase TiC–TiB2 embedded in FCC and BCC matrix. There are also corresponding variations in mechanical properties with structural evolutions. For CoCrCuFeNi(Ti, B4C)0.1 coating, the nanohardness (H) and Young's modulus (E) are 4.19 and 234GPa, respectively. These properties are further improved as function of x content (H=9.14GPa and E=261GPa are achieved in CoCrCuFeNi(Ti, B4C)0.5 coating). The mechanical hardening is accompanied with an increase of the ratio of hardness to elastic modulus (H/E), the yield pressure (H3/E2) and the elastic recovery (η value). An attempt has been made to co-relate the wear resistance of the coatings with H/E ratio and η value.

Electrochemical behaviours of (NiCoFeCrCu)95B5 high entropy alloy coatings

Plasma transferred arc cladding process was used to fabricate (NiCoFeCrCu)95B5 multielement alloy coating. The microstructure and electrochemical behaviours of the coating were investigated. Results show that the precipitation of intermetallic compounds in the coating is effectively inhibited by the rapid solidification process. The coating has simple ordered body centred cubic and face centred cubic solid solution phases. The as prepared coating has excellent corrosion resistance in hydrochloric acid solution. The corresponding corrosion current and corrosion rates are effectively reduced, and the electrochemical impedance is significantly improved referenced to those of the 304 stainless steel.

Microstructure and Electrochemical Properties of CoCrCuFeNiNb High-Entropy Alloys Coatings

The CoCrCuFeNiNb high-entropy alloys coatings were prepared by using plasma-transferred arc cladding process. The microstructure and electrochemical behaviors of the coating were investigated in detail. The experimental results indicated that the coating consists of a simple fcc solid solution phase and an order (CoCr)Nb-type Laves phase. The polarization curves, obtained in 1 and 6 mol/L hydrochloric acid solutions, clearly indicated that the general corrosion resistance of the coating at ambient temperature was better than that of 304 stainless steel. The coating displayed a lower corrosion current and lower corrosion rate. Electrochemical impedance spectroscopy demonstrated that the impedance of the coating was significantly higher than that of the 304 stainless steel.

Effect of Nb addition on the structure and mechanical behaviors of CoCrCuFeNi high-entropy alloy coatings

The microstructure and mechanical properties of the CoCrCuFeNiNb high-entropy alloy coating prepared by plasma transferred arc cladding process were investigated. Two phases are found in the prepared coating with Nb: one is face-centered-cubic solid solution phase; the other is the Laves phase of (CoCr) Nb type. The nano-indentation testing indicates that the microhardness (H), elastic modulus (E), the hardness/modulus of elasticity ratio (H/E ratio) and high resistance to plastic deformation (H3/E2) of the coating with Nb are 6.13GPa, 221GPa, 0.028 and 4.7×10−3 respectively. The CoCrCuFeNiNb coating displays excellent wear and corrosion resistance. The wear resistance of the coating with Nb is about 1.5 times higher than that of the coating without Nb under the same wet sand rubber wheel abrasion testing conditions. Compared with the coating without Nb and as-cast 304 stainless steel, the coating with Nb shows the lowest icorr values in polarization curves and the highest fitted Rf values in EIS plots in 6N hydrochloric acid solution.

Formation and Mechanical Properties of CoNiCuFeCr High-Entropy Alloys Coatings Prepared by Plasma Transferred Arc Cladding Process

Plasma transferred arc cladding process was used to fabricate CoNiCuFeCr multi-element alloys coatings. The experimental results show that the coating forms a face-centered-cubic solid solution phase. The microstructure of the coating is mainly composed of dendrite and discontinuous interdendritic segregation. The average hardness of the coating reaches 194.8 HV100. The nano-indentation testing indicates that the micro-hardness and elastic modulus of the coating are 3.64 GPa and 211 GPa, respectively. The CoNiCuFeCr high-entropy alloy coating has excellent wear and corrosion resistance. The wear resistance of the coating is about 1.7 times higher than that of Q235 steel substrate under the same wet sand rubber wheel abrasion testing conditions. In 1N hydrochloric acid solution, the coating presents lower icorr values in polarization curves and higher fitted Rf values in EIS plots than that of as-cast 304 stainless steel.

High temperature wear of cermet particle reinforced NiCrBSi hardfacings

The aim of the current study was to investigate erosive and impact/abrasive wear behaviour of TiC–NiMo and Cr3C2–Ni reinforced NiCrBSi hardfacings at temperatures up to 700°C.Coatings were produced using plasma transferred arc cladding process. It was shown that the high temperature wear behaviour of TiC–NiMo and Cr3C2–Ni NiCrBSi hardfacings is influenced by oxidation. The formation of mechanical mixed layers and oxide films was observed for both investigated coatings. TiC–NiMo and Cr3C2–Ni reinforced hardfacings show high wear resistance at all testing temperatures for both impact/abrasion and erosion conditions.

Microstructure and dry sliding wear behavior of Fe 2TiSi /γ-Fe/Ti 5Si 3 composite coating fabricated by plasma transferred arc cladding process

Wear resistant Fe 2TiSi reinforced composite coating with a microstructure consisting of fine Fe 2TiSi primary dendrites uniformly distributed in the super fine γ-Fe/Ti 5Si 3 eutectic matrix was in situ fabricated on a substrate of 0.20%C plain low carbon steel substrate by the plasma transferred arc (PTA) cladding process using Fe–Ti–Si–Cr powders blend as the precursor material. Microstructure of the coating was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray energy dispersive spectrometer (EDS). Microhardness along the depth direction of the PTA clad Fe 2TiSi/γ-Fe/Ti 5Si 3 multi-phase composite coating was measured. Room temperature dry sliding wear resistance of the coating was tested. Results showed that the PTA clad Fe 2TiSi/γ-Fe/Ti 5Si 3 composite coating had high and almost uniform hardness distribution along the depth direction of the coating. Under dry sliding wear conditions at an ambient temperature, the PTA clad Fe 2TiSi/γ-Fe/Ti 5Si 3 composite coating exhibited excellent abrasive and adhesive wear resistance.

Effect of electromagnetic stirring on the microstructure and wear behavior of iron-based composite coatings

The effect of electromagnetic stirring on the microstructure and wear behavior of coatings has been investigated. A series of iron-based coatings were fabricated by the plasma-transferred arc cladding process by applying different magnetic field currents. The microstructure and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and wet sand rubber wheel abrasion tester. The experimental results showed that the microstructure of the coatings was mainly the γ-Fe matrix and (Cr, Fe) 7C 3 carbide reinforced phase. The coatings were metallurgically bonded to the substrate. With increasing magnetic field current, the amount of the block-like (Cr, Fe) 7C 3 carbide reinforced phase increased at first, reached a local maximum, and then decreased sharply. When the magnetic field current reached 3 A, the block-like (Cr, Fe) 7C 3 carbides with high volume fraction were uniformly distributed in the matrix and the coating displayed a high microhardness and an excellent wear resistance under the wear test condition.

Microstructure and mechanical characteristics of iron-based coating prepared by plasma transferred arc cladding process

This paper investigated the effect of electromagnetic stirring (EMS) on the microstructure and abrasive wear behavior of iron-based coatings. A series of coatings were prepared by using plasma transferred arc cladding (PTAC) process. The phase and structure of the coatings were characterized by means of SEM, EDXA and X-ray diffraction. The microstructure of the coatings was mainly γ-Fe matrix and (Cr, Fe) 7C 3 carbide reinforced phases. Without EMS, the average size of (Cr, Fe) 7C 3 carbide was about 73 μm, while that of the carbide reached a minimum value of about 20 μm with stirring current of 3 A. The mechanical properties, especially wear resistance, were analyzed in detail. The results showed that the microstructure of the coating plays an important role on abrasive mechanism and the main mechanism is micro-cutting. When the stirring current is 3 A, the coating exhibits excellent wear resistance, which contributes to the good microstructures that hexagonal (Cr, Fe) 7C 3 carbide with the highest volume fraction are uniformly distributed in the matrix. The microhardness of the coatings increase at first, and then decrease as a function of stirring current. The maximum microhardness value of the coating is about 1050 HV.