The Adhesion Evaluation of Thin Hard Coatings on Tool Steel with Nitride or Non-Nitride Layer Using the Scratch Test

The deposition of thin hard coating onto tool steel is done to improve the surface properties such as wear, corrosion. The adhesion strength between substrate and coating is one of important parameters in practical applications since coating failure affects the lifetime of tool directly. Scratch test with acoustic emission(AE) technique was performed to evaluate the adhesion strength qualitative by observing the friction load vs. the normal load curves, the acoustic emission signal generated by the damage of coatings and the scratch track using an optical microscope. In this study, the effect of substrate hardness on the adhesion strength was investigated by evaluating critical load and work of adhesion and observing AE signal and failure mode in scratch track using optical microscope. Coatings were individually deposited on six substrates by means of physical or chemical vapor deposition(PVD, CVD) process and TD process. The critical load of the substrates with nitride layer is higher than without nitride. Although high load causes higher stresses which make flaking occur in the coating-substrate interface, the work of adhesion of harder substrates is also high. Because harder substrates have small contact area causing lower the plastic deformation around stylus.

Microstructure and Properties of Low Temperature Deposit CrxN Using Unbalanced Magnetron Sputtering

CrxN coatings are deposited on the substrates with low temperature using a Teer UDP 550 Close Field Unbalanced Magnetron Sputter Ion Plating system (CFUBMSIP). The effect of applied power on Cr targets related to sample temperature is studied. When the applied power of Cr targets is lower than 1.1KW, the depositing temperature could be controlled at about 180°C. Scratch test shows no coating detachment at the end of scratch track up to 85N load. All results of Rockwell-C indentation indicate that CrxN coating holds good bonding strength. Pin-on-disc tests are performed to evaluate wear resistance of the coatings and no any wear loss can be detected after 6000s and 1800s of running. XRD profile demonstrates that the coating deposited in this study is CrxN.

Influence of Tin-Chloride Pretreatment on Mirror Coating Adhesion

Our research focused on the adhesion properties of mirror coating on silica float glass due to applying different quantity of tin-chloride sensitizing agent. Investigation was carried out to detect the distribution and quantity of tin containing clusters deposited on the glass surface working as crystallization centre. The adhesion properties of coatings were tested by scratch test where critical peeling forces were evaluated. The morphology of the formed scratch track was measured with scanning electron microscope. The surface topography was scanned by AFM technique.

Enhanced Scratch Resistance of Nanocomposite Gelatin Films

Nanocomposites were made using deionized gelatin filled with well-dispersed nanoscale alumina particles. Scratch tests on the nanocomposite films showed substantially improved scratch resistance. Tensile tests revealed increases in both modulus and tensile strength of the nano-filled gelatin films accompanied by a decrease in strain-to-failure. The increase in modulus and strength reduced the degree of plastic deformation during scratch testing, but the onset of periodic cracking in the scratch track was unaffected. Optical transmittance measurements of the gelatin composite showed that the films retained transparency in the visible light range.