| 40Cr alloy steel is widely used in manufacturing various shaft parts due to its high strength,good toughness and plasticity.The surface wear failure of brake camshaft limits the demand of high speed and heavy load of trailer.Therefore,the medium frequency induction quenching technology commonly used to enhance the anti-wear performance of 40Cr alloy steel brake camshaft.However,due to the need to heat the entire surface,the technology has many disadvantages,such as higher energy consumption,high production cost,low processing efficiency and difficult to control heat treatment deformation.Therefore,seeking a simple,environmental protection and efficient method to replace the traditional induction quenching technology has important practical value and theoretical significance.The emergence of bionics provides humans with a key to open nature and learn from nature.Many scientific research and engineering problems seek answers in nature.Through the imitation of the natural organisms with good wear resistance to reproduce their body surface functions,improve the surface performance and prolong the service life of mechanical parts.Inspired by this,this research group is committed to the preparation of biomimetic surface with various morphology and structure on materials by using laser technology,thus improving the properties of materials.Based on the bionic principle and laser surface texturing technology,this paper proposes a new laser bionic texture technology that may replace the induction quenching technology to improve the wear resistance of brake camshaft.In the process of laser bionic texture strengthening,the microstructure of the substrate material changes and the hardness increases,which is similar to the independent hard strengthening phase on the surface of the prototype wear-resistant biological body in nature,and forms the bionic texture surface with soft-hard and rigid-soft phase.First,through the biomimetic design,we can further study the wear condition of the sample under different morphological couplings and compare with the traditional induction quenching technology,to verify the best biomimetic texture sample.Secondly,the influence of coupling characteristic parameters(distribution distance and distribution angle)on the anti-wear performance of the new bionic coupling 40Cr alloy steel brake camshaft is studied.Thirdly,the influence of distribution angle on the tensile properties of 40Cr alloy steel with bionic texture is studied.The relationship equation of the tensile properties of bionic texture samples with respect to the distribution angle is established.The effect of distribution angle on the enhancement effect of bionic texture sample is discussed.Finally,through the control of different laser energy density,adjusting the process parameters of laser processing,getting the microstructure and hardness of different bionic texture,the width,depth and cross sectional area for fitting under different laser energy density,meanwhile obtaining the relationship equation between bionic texture feature parameters and the laser energy density within a fixed parameter range.Furthermore,The influence of different laser energy densities on the anti-wear performance of 40Cr alloy steel is studied.The main conclusions are as follows:1.The influence of morphological coupling element on the anti-wear performance of bionic texture specimens is illustrated.The internal structure of the bionic texture is transformed into martensite by the original pearlite+ferrite under the action of high-energy laser,and the obtained microstructure is uniform and compact,and the grain is also refined,and the micro-hardness is improved.It is three times as hard as the untreated sample.Compared with the induction quenching samples,the average micro-hardness values of the striped and reticulated bionic samples is increased by 28.57%and 33.93%,respectively.The excellent properties of biomimetic texture samples depend on the grain refinement and phase transformation strengthening during laser rapid heating and cooling.Compared with the untreated sample,the reticulated bionic texture sample has the smallest wear loss weight and the best improvement effect on the wear resistance.The improvement degree of the anti-wear performance of the sample is up to 73.83%.The second is the striped bionic texture sample whose wear resistance improved by 70.22%.Thirdly,the anti-wear performance of induction quenching sample improved by 62.47%.Compared with the sample of induction quenching,the anti-wear performance of the sample with reticulated bionic texture improved by 30.28%.In the wear direction,the bionic texture of reticulated forms an obvious soft and hard bionic model,and at the same time plays a continuous supporting role,so it has the best anti-wear performance.2.The influence of coupling distribution distance on the anti-wear performance of bionic textured specimens is expounded.The relation equation between the anti-wear performance of bionic textured samples and the distribution distance is established as follows:yWL=15.88571-5.01143d+1.64286d2;When the distribution spacing is within the range of 2mm?d?4mm,the anti-wear performance of the material is related to the strengthening area of the laser bionic texture,and the strengthening area is dominant.The anti-wear performance of the material increases with the decrease of the distribution distance.When the distribution distance is within the range of 0mm?d?2mm,the inconsistent deformation between the hard phase and the soft phase plays a dominant role,and the wear resistance of the material decreases with the decrease of the distribution distance.Therefore,when the distribution distance is d=2mm,the anti-wear performance of 40Cr alloy steel reinforced with bionic texture is the best.3.The mechanism of the coupling distribution angle on the anti-wear performance of the bionic textured specimen is revealed.When bionic textures and wear direction intersecting arrangement,surface stress dispersion to an infinite number of shear stress plane is the most effective to reduce the stress concentration phenomenon.In addition,the intersection of bionic texture can provide continuous support for the roller in the process of wear and tear,eliminate the possibility of direct contact with the roller and base and significantly improve the service life of 40Cr alloy steel.4.It is clarified that the laser biomimetic texture technology can improve the strength and plasticity of 40Cr alloy steel simultaneously.The relationship between distribution angle and tensile properties of 40Cr alloy steel is revealed.It is found that stripe bionic texture strength effect is influenced by the distribution angle.When the stripe shape bionic texture is parallel to the tensile direction,namely,? is 0°,bionic texture sample T1 strengthen effect is best,the yield strength(YS)and tensile strength(TS)reach maximum,compared with the untreated sample,the yield strength increased by 24.77%,the tensile strength increased by 20.73%.With the increase of distribution angle,the yield strength(YS)and tensile strength(TS)of the biomimetic texture samples decrease,but the elongation increases.When the striped bionic texture is perpendicular to the tensile direction,i.e.,a is 90°,the plastic deformation resistance of T5 specimen increases significantly,and the elongation(EL)reaches the maximum value,which increases by 48.98%compared with the untreated specimen.In addition,through regression analysis,the relationship equation of the tensile properties of bionic texture samples with respect to the distribution angle is established:The linear relationship between the yield strength and the distribution angle of the bionic texture sample:yYS=679.69672-0.69754?The relation equation between the tensile strength of bionic textured samples and the distribution angle is established as follows:yTS=792.82787-0.7959?The quantitative relationship between elongation and distribution angle of bionic texture samples:yEL=18.48187+0.07372?-0.000393444?2The significance test shows that the confidence of the regression equation can reach 99%.5.The influence of different energy densities on the anti-wear performance of bionic texture specimens is discussed.Energy density is the main factor that affecting surface forming quality.When the laser energy density is 18.00-3 +3J/mm2,the laser bionic texture technology can effectively obtain better surface forming quality and the arithmetic mean of surface roughness is 1046.81nm.With the increase of energy density,the width,depth and area of the cross section of bionic texture increase.Through fitting the influence law of energy density on the width,depth and area of the cross section respectively,and establishing the mathematical models respectively.The relationship equation of the width of the cross section with energy density is obtained:;ywidth=2.01854+0.0743x;The linear equation expression of the cross-section depth with energy density is as follows:ydepth=0.26422+0.02609x;The linear equation of the area of a cross section as a function of energy density is as follows:yarea=-0.0974+0.1013x.At the same time,the hardness of bionic textured samples S1 to S5 increased by 194.55%,205.45%,220.45%,228.64%and 239.09%,respectively,compared with the matrix hardness.The composite strengthening effect of grain refinement and martensitic transformation makes the biomimetic texture samples have good mechanical properties.Moreover,with the increase of energy density,the wear weight loss of the sample decreases.Compared with untreated samples,the weight loss reduction percentage of S1 to S5 bionic texture samples decreased by 64.71%,67.97%,71.90%,73.20%and 73.86%,respectively.This indicates that the existence of bionic texture can significantly improve the anti-wear performance of the sample surface.Moreover,with the increase of laser energy density,its anti-wear performance increases. |
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