During forging operations, strain can occur through three primary mechanisms: strain due to load applied through dies, strain due to thermal contraction, and strain due to creep. In materials behavior models, strain due to applied load and thermal contraction are directly considered and predictions are based on thermophysical properties and flow stress behaviors as inputs to the models. Strain due to creep after forging (during cooling) is often more difficult to predict and capture due to lack of materials data. In particular, data that capture the changing flow stress behavior during cooling (rather than from isothermal testing) are not commonly available. In this project, creep strain behavior during cooling was investigated by physical simulations using a Gleeble 3500. Standard cylinder-shaped Ti-6Al-4V samples with 10 mm diameter were heated to below β-transus temperature (1775°F) or above β-transus (1925°F), followed by constant cooling rates of 250°F/min and 1000°F/min with and without applied load during cooling to 1000°F. Total strain for the tests ranged from 2 – 6%. Characterization of prior microstructure and texture was carried out using XRD, optical microscopy, and SEM. The results provide insights on the relationship of flow stress behavior and microstructure as a function of temperature and cooling rate and are applicable to forging practices. These materials data can be used as input for future process modeling, potentially giving better prediction accuracy in industry applications.

This study evaluates the thermal and mechanical properties of plasma-sprayed lanthanum zirconate thermal barrier coatings and compares them with conventional 8YSZ TBCs. The La 2 Zr 2 O 7 coatings were found to have a lower thermal conductivity than 8YSZ, although this is offset by lower bond cap tensile strength and poor erosion resistance. A double-layered structure with a La 2 Zr 2 O 7 coating on porous YSZ was also tested and is shown to have better thermal shock performance than single-layer La 2 Zr 2 O 7 and double-layer structures formed on dense 8YSZ sublayers.

TiAl 3 -Al composite coatings are believed to hold promise for extending the service temperature range of titanium alloys used as structural materials. In this study, 0.6 x 40 mm Ti-6Al-4V specimens are coated with a 30 μm thick layer of TiAl 3 -Al by low-temperature HVOF spraying. Cross-sectional imaging shows that the as-sprayed coatings have a dense laminar microstructure and are well bonded to the substrate. Following the initial examination, the coating samples were placed in a muffle furnace, where they were held at 700 °C for up to 1000 h. Mass gain was detected starting at 200 h and remained nearly constant for the remainder of the test. This is an indication of excellent corrosion resistance, which is verified by SEM cross-sectioning and elemental EDS analysis. A brief explanation of the protective mechanism of the coating is provided.

B 4 C-Ni powders ranging in content from 5-60 wt% Ni were fabricated by pressurized hydrogen reduction and deposited on mild carbon steel substrates by air plasma spraying. The microstructure, morphology, and phase composition of the powders and coatings were evaluated by means of SEM and XRD analysis. The influence of Ni content on coating microstructure, fretting wear resistance, hardness, and adhesive strength was investigated in detail. The results show that Ni affects fretting wear resistance, which was found to be highest in the coating with 40 wt% nickel. The B 4 C-40Ni coating also proved superior in terms hardness, porosity, and friction coefficient, although its adhesive strength was the lowest.

In this study, cold sprayed Cu approximately 40 to 60 μm in thickness is deposited on 6063 and LD10 aluminum plate to improve wettability for low temperature soldering and to serve as a barrier layer to protect the substrate from gallium diffusion originating in the solder paste. The effect of the coating on wettability, diffusion, solder joint interface microstructure, and shear strength is investigated in detail.

Sub-micro-structured titanium nitrides (TiN) coatings on Al 2 O 3 substrates were fabricated by vacuum cold spray (VCS) process using ceramic powders, which were ball-milled at room temperature. The microstructure features and crystal structures of the VCS TiN coatings were analyzed by scanning electron microscopy and X-ray diffraction. The adhesion between the coating and the substrate was evaluated with a scratch tester. The sheet resistance of the VCS TiN coatings was measured by using a four-point probe method. The effects of nozzle traverse speed on the microstructure, adhesion to substrate and electrical properties of the coatings were investigated. It was found that the adhesion improves greatly with the nozzle traverse speed increasing from 5 to 15mm/s, and the electrical resistivity levels of the coatings is decreased significantly. The resistivity of sub-micron-structured TiN coatings is substantially lower than those of nano-structured ones fabricated by the same VCS process. And a minimum resistivity of 1.16×10 -4 Ω·m is achieved.

Thermal barrier coatings (TBCs) consisting of a yttria-partially-stabilized zirconia (YSZ) topcoat and a metallic bond coat are used to protect components in high temperature environments such as the hot section of a gas turbine. In this study, the bond coats have been fabricated using different thermal spray processes, including vacuum arc spaying, high-velocity oxyfuel flame spraying, low-pressure plasma spraying, air plasma spraying, and detonation spraying. The microstructure of the resulting TBCs is characterized based on XRD, SEM, and TEM analysis and various properties are measured, including high-temperature oxidation, cohesion strength, thermal impact, and heat insulation temperature.

Nickel clad hexagonal boron nitride (h-BN) powders were prepared by reducing nickel ions from a solution under hydrogen pressure in the presence of ammonia as a complexing agent, and plasma spraying was carried out to deposit the corresponding coating. The microstructure, morphology and phase composition of the powders and the coating were characterized by optical microscope (OM), Scanning Electronic Microscope (SEM) and X-ray Diffraction (XRD), respectively. The results show that alkali solution pretreatment and activation procession are necessary for acquiring a dense and uniform nickel coating on the surface of the h-BN particles, and the h-BN particles are distributed well throughout the coating with the porosity of about 26%, which indicate that the coating was potential for abradable sealing application.

Thermal spraying technology was one of the listed advanced manufacturing technologies to be developed with great effort in “the eleventh five-year” programming and the perspective layout for the years to 2020 of China. It is also a very important technology to promote establishment of economical society. This paper analyzed some application cases of thermal spraying technology to several typical components such as the corrugated roller used for packaging industry, injection molding screw for plastic industry, insulated bearing for railway industry and ball valve with large diameter for petroleum & chemistry industry which were practiced by Surface Engineering Research Institute of CAAMS in recent years. This paper presented some new developments on applications of thermal spraying technology in China and some considerations on the developing trends of thermal spraying applications in China in future are put forward in comparison with the current situation of oversea thermal spray practices.

In this paper, composite thermal barrier coatings (TBCs) of Al 2 O 3 +ZrO 2 are deposited on SS304 stainless steel substrates by gas tunnel type plasma spraying. The resultant coating samples prepared with different Al 2 O 3 +ZrO 2 mixing ratio and thickness are compared in corrosion resistance. A potentiostatic anodic polarization corrosion tester is used to get the corrosion characteristics of coated samples to measure their corrosion resistance. From the polarization curves, corrosion potential and deactivated corrosion current density are obtained and analyzed corresponding to the microstructure of the coatings. The results show that the higher alumina content and thicker coatings, the better the corrosion resistance, which is attributed to the diffusion resistance of coating layers to corrosion reaction. The coating microstructure is characterized using an optical microscope imaging system and measured the coating thickness and porosity. The coating porosity and thickness are believed to be the important factors for the variation on the corrosion behavior of Al 2 O 3 +ZrO 2 coated SS304 stainless steel substrates.