Effect Of Liquid Water On Tribochemical Behavior Of Phosphate Laser Glass

Nd-doped phosphate laser glass has been successfully used in a number of high-peak-power laser systems including the "National Ignition Facility" manufactured in America and the "Shenguang" series devices manufactured in China due to its excellent optical properties.At the same time,ultra-high surface finish quality is required for Nd-doped phosphate laser glass,such as super smooth,no defects and so on.The polishing of the phosphate laser glass is carried out in the polishing solution or in the coolant,so the water molecules in the liquid will inevitably affect the material removal process on the glass surface,thereby affecting the material removal of the glass.Therefore,it is necessary to study the effect of liquid water on the material removal of phosphate laser glass and to explore the potential wear mechanism.In this paper,aluminum oxide ceramic balls were used as friction pairs to study the material removal law of phosphate laser glass in dry air and liquid water environment,and the potential wear mechanism under these two conditions was further revealed by comparison and analysis.Firstly,the removal law of phosphate laser glass in dry air and liquid water environment was explored under different load conditions.Secondly,the friction and wear properties of phosphate laser glass and K9 glass(as known as BK7 glass,is a typical borosilicate glass with better chemical stability and water resistance,whose chemical properties are completely different from the phosphate glass.)in dry air and liquid water were studied under the same load conditions,and reveal the effect of liquid water on the material removal of phosphate glass.Finally,according to the results of liquid water on the removal and damage of phosphate laser glass,and the results of chemical detection,the effect of the chemical structure and chemical stability of the glass on the removal of phosphate laser glass material was revealed.Based on the above research,the main conclusions of this paper are asfollows:1)As the load increases,the wear depth and wear volume of the phosphate laser glass in the dry air environment are much smaller than those in the liquid water environment,while the subsurface damage in the dry air is greater than that in the liquid water environment.The analysis results shows that water-induced stress corrosion promotes the material removal of phosphate laser glass,and the reduction of shear stress caused by water lubrication weakens the damage of the subsurface.2)Under the same load conditions,the liquid water will promote the wear of phosphate glass and inhibit the wear of K9 glass.Water-induced stress corrosion promotes the material removal of phosphate glass,but weakens the material removal of K9 glass.The boundary lubrication effect of the water film weakens the shear stress between the interfaces,which weakens the subsurface damage of the phosphate glass and K9 glass.3)Compared with the K9 glass mainly composed of Si-O-Si hinges,the chemical stability of the phosphate glass is poor,and its net structure is more likely to be destroyed by the water molecules.Hydrolysis and tribochemical wear are more likely to occur in the phosphate glass,which promote its material removal.