Abstract: In order to study the feasibility of kraft paper as watercolor paper, the wetting properties, mechanical properties and friction properties of kraft paper and watercolor paper were compared before and after aging. The aging test was carried out on kraft paper and the watercolor paper by aging chamber, the wetting properties of distilled water and three watercolor solutions before and after aging of kraft paper and watercolor paper were compared, tensile tear test of paper on the tensile testing machine, the fracture changes of paper were analyzed by scanning electron microscope, the friction tester performs the paper friction test. The results show that both kinds of paper are amorphous, watercolor paper was showed hydrophobicity before and after the aging, the contact angle was maintained at about 119,09° ± 5° in four different solutions, unaged kraft paper exhibited hydrophilicity, the aged kraft paper showed hydrophobicity with a contact angle of 92,52° ± 1°，the aged kraft paper shows better performance in both tensile and tearing aspects and tensile strength is 20 MPa higher than watercolor paper, the surface roughness of kraft paper is higher than watercolor paper. The experiment is helpful for the market to consider whether the cheaper kraft paper replaces the more expensive watercolor paper in some aspects and provides some scientific reference value for future research.

This paper presented a study of friction and wear on 9Cr18Mo when rubbed against other materials (steel-304, steel-440C, steel-GCr15 or silicon nitride ceramic ball) at high temperature conditions. Friction and wear tests were carried out with universal a friction and wear testing machine. The wear morphology was analyzed by a Nanovea three-dimensional profilometer and trinocular positive Gang metallurgical microscope. The Vickers hardness of 9Cr18Mo at different temperatures was tested by means of a high temperature vacuum hardometer. Results showed that the friction and wear on the contact surface of the 9Cr18Mo sample are higher when the hardness of counter materials is higher than or similar to that of the sample. Under dry sliding conditions, the 9Cr18Mo sample surface presented various degrees of adhesion, plowing and pit, particularly if tested in the presence of a high temperature environment. During the worn stages, the counter materials on the worn surface successively produced cracks, crack growth, and wear debris under the action of load. Moreover, the frictional pair 9Cr18Mo-ceramic showed good anti-wear behavior at 400 °C that proved the anti high temperature performance of 9Cr18Mo.