Ni20Cr splats were sprayed onto polished substrates at different preheating temperatures in an argon atmosphere by Low Pressure Plasma Spray to reveal the dominating factor on the effective interface bonding formation. The splat morphology, microstructure and splat-substrate interface bonding were characterized by SEM and EBSD. The interface for examination of typical splats was prepared by FIB. Disk splats were obtained on AISI 304 stainless steel substrates preheated to temperatures of 100 °C (cooling from 350 °C), 350 and 550 °C. Moreover, typical distinct two-zone microstructure feature was observed on the splat surface by SEM and EBSD, including central coarse grain and marginal fine grain. When the preheating temperature was higher than 350 °C, effective bonding formed only in the entire central coarse zone, whereas no effective bonding was observed in the fine grain zone. By using glass, copper, nickel and 304 SS as substrates, it was found that increasing thermal conductivity of metallic substrates has little effect on splat diameter and morphology and however decreased the area fraction of central coarse grain zone. It was revealed that the melt/substrate interface temperature plays a crucial role on the interface bonding formation.

The CoCrAlSiY alloy powder with Si mass concentrations of 0, 2% and 5% was prepared in this work. The oxidation kinetics curves of all three kinds of powders after 300 h oxidation at 1000 °C were plotted. In addition, the phase constitution of alloy powder and the distribution of β phase were analyzed by SEM and EDS. Furthermore, the effect of Si-addition on the melting temperature and oxidation resistance of the alloy powder were investigated by DSC-TG from the room temperature to 1400 °C. And the element concentrations at the grain boundary of alloy powder with Si addition of 2% were also analyzed. The results show that the melting temperature of alloy powder decreases as increasing Si content, which indicates that adding Si element could influence on the selective oxidation of Al and Cr elements in the alloy system, and improve the oxidation resistance of CoCrAlY powder. In addition, the weight gain of powder with Si addition of 2% is lowest. And Si element has a enrich tendency in the grain boundary. Therefore, the higher Si content would have a negative effect on the high temperature oxidation resistance of powder.

In this work, pure silicon and Ni-P coated silicon powders were cold sprayed on copper foil. To thicken coating layers, 2-pass and 3-pass coatings were carried out. In the case of Ni-P coated silicon powders, coated anodes show excellent charge-discharge characteristics after two passes. For the pure silicon powders, however, even if a 2-pass operation is performed, the additional attached silicon mass is only 2~3 %. This means that multi-pass spraying is not an effective way to increase the thickness of pure silicon coatings produced by cold spraying.

WC-Co and WC-Co-Cr coatings were deposited on Q345 steel substrates by HVOF and plasma spraying. Coating hardness was measured and corrosion and wear tests were conducted. In terms of hardness and density, the HVOF sprayed WC-Co coating is shown to be superior to its plasma sprayed counterpart. The WC-Co-Cr coatings, on the other hand, exhibited better wear and corrosion resistance, especially the coating produced by HVOF spraying.

In this work, atmospheric plasma spraying was used to deposit an equiatomic AlCoCrFeNiTi high-entropy alloy (HEA) coating with a thickness of 236 μm, a porosity of 1.6%, and an adhesive strength of 50.3 MPa. The as-sprayed coating mainly contained BCC1 and BCC2 phases, with only a trace amount of the FCC phase. Microhardness was four times that of 316 stainless steel and the volume wear rate at room temperature was one-fourth that of the substrate material. The wear rate decreased with increasing temperature from 25°C to 700°C, then increased from 700°C to 900°C. Over that range, the wear mechanism changed from delamination wear to oxidation and adhesion wear.

This paper aims to clarify the development and characterization of cold-sprayed aluminum coatings on a non-regular medium-carbon steel surface. The work is carried out with a two-fold purpose: to optimize the deposition process and coating thickness and to learn how substrate defects and imperfections influence coating performance and the corrosion resistance of the coated material.

Aluminum-titanium powder mixtures were deposited on γ-TiAl alloy substrates by cold spraying then heat treated for 5 h at 600, 650, and 700 °C. SEM and XRD examination showed that the treatment caused Al to diffuse into the substrate where it reacted with Ti, resulting in changes in microstructure. The diffusion of Al left pores in the fringes of the TiAl 3 phase, increasing the porosity of the coatings. A surplus of Al remained in the coatings after heat treatment at 600-650 °C, but at 700 °C, all Al was consumed, contributing to the formation of a continuous TiAl 3 layer.

This study investigates the microstructure, thermal conductivity, hardness, and strength of Cu-Cr-Zr coatings produced by cold gas spraying. The elements in the powders were found to have a significant influence on microstructure, particle morphology, and strengthening mechanisms. The strengthening mechanisms of copper alloy coatings include fine crystal reinforcing, solution strengthening, work hardening, and dispersal reinforcing. Different mechanisms are shown to be more or less effective depending on powder composition and the presence of impurities. By filtering impurities before gas atomization, the thermal conductivity of as-sprayed Cu-Cr-Zr coatings can be improved by a factor of two.

In the present work, a mechanical alloying (ball milling) method was developed to synthesize NiCrBSi-WC composite powders for HVOF spraying. Coating properties and microstructure are shown to vary with composition and initial powder size prior to ball-milling. With nanometric particles, metallic and carbide powders appear to be intimately linked with WC, forming a highly protective layer. Conversely, with micrometric powders, ball-milled particles appear more fractured and regularly dispersed inside the matrix.

In this work, tunnel plasma spraying is used to produce Cu 36 Zr 48 Al 8 Ag 8 metallic glass coatings on stainless steel. The results show that cooling gas flow rates play a vital role in oxidation and the formation of intermetallic phases in coating microstructures. Phase formation and microstructural features were evaluated by XRD and SEM-EDX analysis. Coating properties including hardness, sliding wear, and corrosion resistance were measured and the results are compared with the presence of secondary phases. It is shown that an increase in secondary phases improves sliding wear resistance but reduces resistance to corrosion.

This study evaluates the friction and wear behavior of iron-base coatings produced by arc spraying using experimental cored wires. Coating microstructure was analyzed and various wear tests were performed. The results show that the tribological properties of the ferrous coating materials are greatly affected by porosity, oxide inclusions, particle shape, and microhardness.

The FeAl intermetallic compound coatings were sprayed by low pressure plasma spraying (LPPS), air plasma spraying (APS) and high velocity oxy-fuel spraying (HVOF). The influence of three kinds of thermal spraying processes on the microstructure, microhardness, elastic modulus and fracture toughness of coatings were investigated. The results showed that the APS and HVOF coatings exhibited similar microhardness, about 540HV 0.3 , which is much lower than that of LPPS coatings, 860HV 0.3 . The elastic modulus measured for APS, HVOF and LPPS coatings using Knoop indentation were 96, 84, 176GPa, respectively. The APS coatings were also observed to have lower elastic modulus values in the in-plane direction than those in the perpendicular direction, as a result of microcracks scattered within the coatings. In fracture toughness tests, the LPPS coatings revealed the lowest fracture toughness, as compared with other two spraying processes, indicating low porosity and crack levels are related to low fracture toughness. From these results, it appeared that potential improvements to certain mechanical properties can be achieved using low pressure plasma spraying process.

Oxidation is a serious issue for thermally sprayed alloy coatings, especially in atmospheric plasma spray (APS) process, by which it is believed to be impossible to obtain alloy coatings with low oxide content. Oxidation behavior of Ni20Cr alloy and NiCrSiBC alloy in APS were compared by evaluating collected in-flight particles and sprayed coatings in our previous study. The results clearly show that the oxide content in the in-flight particles and coating of NiCrSiBC alloy was significantly lower than that of Ni20Cr alloy. In the present study, further study of the surface oxide layer of NiCrSiBC coating was carried out by TEM, which showed 10 nm thick oxygen enriched layer. The effects of particle temperature and velocity on the oxidation of the NiCrSiBC alloy were investigated. It was found that increasing particle temperature and velocity did not affect the oxidation of inflight particle of the NiCrSiBC alloy but significantly increased the oxidation after particle impacting substrate. The results are discussed in conjunction with effectiveness of preferential oxidation of Si, B, C and simultaneous vaporization of the formed oxides on suppressing in-flight oxidation and influence of a large amount of sub-particles produced upon impacting substrate on oxidation characteristics when increasing plasma power.