Study On Wear Resistance Of 7075 Aluminum Alloy Processed By Laser Biomimetic Coupling Technique

With the increase in drilling depth,the aluminum alloy drill pipe has gradually replace steel drill pipe in applications such as ultra-deep wells and extended reach wells owning to the corresponding low density,light weight,and high specific strength.However,compared with the steel drill pipe,there were serious wear between aluminum alloy drill pipe and casing and stratum aggravates during the process of drilling operation because of the lower hardness and poor wear resistance,which limits the promotion and application of the aluminum alloy drill pipe.According to the related studies on biomimetic,certain animals with non-smooth surface have better wear resistance for thousands of years of evolution.In the further research found that the non-smoth surface was distributed alternatively the softer and the harder points.Our research group has been working on the laser biomimetic coupling research.Based on the bionics,various units with different structures,shapes,and properties were processed by laser technique,which has been successfully used in the improvement of wear resistance,fatigue resistance,and mechanical properties of materials.Inspired by this,on the basis of predecessors'research,the study applied the laser biomimetic coupling technique to the 7075 aluminum alloy drill pipe to improve the corresponding wear resistance and explore the wear mechanisms.The study set attention to the influence of the biomimetic structure,the biomimetic shape and the relevant characteristic parameter on the wear resistance of 7075 aluminum alloy.In the research,various laser energy densities were inputted to fabricate biomimetic units with different structure,sizes,hardness and properties and the mechanism of effects were explored.Secondly,five shape kinds of biomimetic units with the same proportion of area and five different proportion of hard phase areas with the same biomimetic unit shape were designed in the paper.Moreover,the wear experiment was combined with finite element analysis to analyze the mechanism of wear resistance.The study shows that the wear resistance of 7075 aluminum alloy has been improved to varying degrees through laser biomimetic coupling processed.The mechanical properties and wear resistance of the material were greatly improved with the condition of laser energy density was 420.1 J/cm~2.In addition,in the case of the same proportion of the area of the unit,the unit with the composite form has better wear resistance,and the wear resistance of the spot and reticulation combination is the best;And in the case of the same striation unit,the wear resistance of the biomimetic samples was excellent with the proportion of the hard phase 40%to 60%.In addition,the corresponding wear mechanism was mainly divided into the following aspects:the harder biomimetic units played a role of skeleton support during the process of wear,hindered the continuity of debris movement and the contact between the debris and the matrix,thus protecting the matrix.In conclusion,the role of the units skeleton supported was mainly related to the structure,size,hardness and tensile properties of the unit;secondly,the biomimetic units with various shape and characteristic parameter have an influence on the stress distribution on the specimen surface.The more stress the biomimetic units born,the smaller that the substrate born,the better the protection effect on the substrate of the biomimetic unit,and the more improvement on the wear resistance of the material.