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Scratch tests were performed on thermal-resistant hard Si–C–N coatings deposited on steel (SS) 304, by radio frequency (RF) magnetron sputtering. The abrasion and wear properties were studied by analyzing the changing failure complexion inside the scratch showing a mixture of ductile and brittle properties. The change in loading rate caused noticeable changes in the failure mode. The plasticity was found to have a peripheral domination initially with an increase in load but was replaced by brittle failure on increasing the loading rate. The work of adhesion and wear rate were determined.

Lead-free piezoelectric (Bi_1/2Na_1/2)TiO₃ (abbreviated as BNT) films were deposited on 0.2 mm thick pure titanium(Ti) substrates by a hydrothermal method. Scratch tests and Vickers indentation tests were performed to quantitatively assess the adhesion strength between BNT films and Ti substrates. Some of Ti substrates were pretreated by chemical polish and mechanical polish respectively prior to BNT film deposition with a view of investigating the effects of substrate surface pretreatments on the adhesion of BNT films. In the scratch test, the critical force was determined from the variations of the tangential force and the acoustic emission (AE) signals with the normal force. The scratch test results revealed that the chemical polish pretreatment effectively improved the adhesion of BNT films. In addition, the critical substrate strain inducing the adhesion failure of BNT films has been investigated by the Vickers indentation test combined with finite element analysis (FEM).

In the present paper, the influences of different double layer on wear and scratch performances of commercially pure Titanium (CP-Ti) were investigated. TiO₂/SiO₂ and SiO₂/TiO₂ double layer coatings were deposited on CP-Ti by sol–gel dip coating process and calcined at 750${}^{\circ }$C. The phase structure, cross-sectional morphology, composition, wear track morphologies, adhesion properties, hardness and roughness of uncoated and coated samples were characterized with X-ray diffraction, scanning electron microscopy (SEM), nano-indentation technique, scratch tester and 3D profilometer. Also, the tribological performances of all samples were investigated by a pin-on-disc tribo-tester against Al₂O₃ ball. Results showed that hardness, elastic modulus and adhesion resistance of double layer coated samples were higher than untreated CP-Ti. It was found that these properties of TiO₂/SiO₂ double layer coatings have higher than SiO₂/TiO₂ double layer coating. Additionally, the lowest friction coefficient and wear rates were obtained from TiO₂/SiO₂ double layer coatings. Therefore, it was seen that phase structure, hardness and film adhesion are important factors on the tribological properties of double layer coatings.

In this paper, the surface damage mechanism of silicon carbide lapping process was studied. A theoretic model between the depth of subsurface damage and surface scratch of silicon carbide substrate double-side lapping has been built. An experiment of two-sided lapping combining VK-X100/X200 shape measurement laser microscopy system with HF mild chemical etching experiment on SiC substrate was processed to obtain the distribution of surface scratch and subsurface damage layer with depth. The study shows that the thickness of subsurface damage layer decreases as the depth increases, which centrally distributes in the depth of 0–15.6 μm from outer fragmentation and scratch damage layer, which accounted for about 98.6%. The result can help us to optimize processing parameters of silicon carbide substrate double-side lapping to control the depth of subsurface damage layer.