Papers by Keyword: NiCr

Abstract: Twin Wire Arc spraying (TWAS) is a well-established method to deposit metallic coatings to protect mechanical components from wear and corrosion. In this work were used coatings that can be divided into two groups: FeCr-based ones and NiCr-based ones. The microstructure, and mechanical properties such as hardness, adhesion, abrasion and erosion resistance were evaluated on these coatings. The wear behavior of the coatings was investigated by Solid Particle Erosion resistance test and by Dry sand/Rubber wheel abrasion test. The aim of this work is to study the wear mechanism by SEM observation of worn tracks.

Abstract: Wear behavior of the HVOF deposited NiCr and Stellite-6, coatings on Fe-base alloy steel were evaluated by the pin-on-disc techniques. The coatings were significantly harder and less porous. SEM/EDAX and XRD techniques were used to analyse the worn out surface and wear debris. The Fe₂O₃ was identified as the major phase in the wear debris. The wear mechanism is mild adhesive wear in nature. The coatings protected the substrate steels against the adhesive wear significantly.

Abstract: NiCr/NiSi functional thin films of temperature measurement of cutter sensor were prepared by means of advanced Twinned microwave ECR plasma source enhanced Radio Frequency (RF) reaction non-balance magnetron sputtering technique. Fabrication technologies of NiCr/NiSi thin films were studied. The Compositions, micro-morphology, general structure and depth of NiCr/NiSi thin films were analyzed by means of Electron Probe, SEM, AFM, step profiler and stereo vision micro operation system. The results showed that NiCr/NiSi thin-films were small depth, uniform compact, smooth and good continuity, composition of which was close to target.

Abstract: Formation of NiCr nanorings out of 2-3 nm NiCr nanoparticles prepared by DC magnetron sputtering with inert gas condensation is reported. An RF quadrupole mass filter has been used to get the particle size distribution and control the particle size in the plasma stream of grown material. The depositions are made on silicon substrates at room temperature under a helium and argon atmosphere of varying composition. By optimizing the He-Ar composition, magnetron power and the condensation zone, the particle size distribution is narrowed. Magnetic characterization determines that every single nanoparticle possesses a single magnetic domain that influenced their arrangement on the substrate. These arrangements were particularly in ring like structures. Particles join together while being deposited to form rings with a ~100 nm diameter. Particle density and agglomeration phenomena depend on the substrate’s time of exposure to the NiCr nanoparticle source coming from the target.

Abstract: Using Raman microprobe spectroscopy made it possible to study the buckling phenomenon in chromia films grown at 900°C in air from a Ni30at%Cr alloy. Blisters have been optically observed to be circular and, from the top view, the mean radius has been measured with an accuracy of about 1%m. An autofocus device allows the characterisation of the profile of each blister and the shift of the A1g Raman peak of chromia gave the local stress far from the blister and all along the buckled zone. From these observations, the induced spalling has been related to the blister morphology.

Abstract: There is an increasing reliability concern of thermal stress-induced failures in multilevel coatings in recent years. This work reports investigations of cracking of NiCr coatings due to thermal cycling. The temperature cycling in accelerated testing was performed in three temperature range of 150, 175 and 200°C. The NiCr coatings were considered to have failed when the sheet resistance changed by 30% relative to an initial value. As the cyclic repetition of thermal shock increased, the sheet resistance of NiCr coatings increased. The Coffin-Manson equation was applied to the failure mechanism of cracking of NiCr coatings and the SEM observation of cracks and delamination in NiCr coatings due to thermal cycling agreed well with the failure mechanism.