Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall ...Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall performance for applications such as aerospace satellite parts,shafts,gears,and bushings.The addition of functional fillers can overcome the limitations of single-polymer coatings and extend the service life of the coatings by providing a combination of low friction,high wear resistance,high load bearing,high temperature resistance,and high adhesion.This paper compares the heat resistance,and the tribological and mechanical properties of common polymer matrices,as well as the categories of functional fillers that improve the coating performance.Applicable scopes,process parameters,advantages,and limitations of the preparation methods of polymer coatings are discussed in detail.The tribological properties of the composite coatings with different matrices and fillers are compared,and the lubrication mechanisms are analyzed.Fillers reduce friction by promoting the formation of transfer films or liquid shear films.Improvement of the mechanical properties of the composite coatings with fillers of different morphologies is described in terms of strengthening and toughening mechanisms,including a stress transfer mechanism,shear yielding,crack bridging,and interfacial debonding.The test and enhancement methods for the adhesion properties between the coating and substrate are discussed.The coating adhesion can be enhanced through mechanical treatment,chemical treatment,and energy treatment of the substrate.Finally,we propose the design strategies for high-performance polymer composite coating systems adapted to specific operating conditions,and the limitations of current polymer composite coating research are identified.展开更多
Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with diffe...Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with different morphologies,were investigated by X-ray diffractometer （XRD）,scanning electron microscopy （SEM） and electron probe micro analyzer （EPMA）. In addition,the effects of the addition of Y on mechanical properties （in terms of microhardness and the cracking susceptibility） were also highlighted. The results showed that the coatings were composed of α-Ti cellular dendrites,coarse needle-shaped TiB phase and an eutectic in which a large number of needle-shaped TiB whiskers and a few equiaxial TiC particles were uniformly embedded. Y was not stable and was transformed into Y2O3 during laser cladding. The addition of Y could refine the microstructure of the coating by hastening the spheroidization of primary phase structure. Moreover,it could also decrease the activity of carbon and prevent solute atoms from traversing the interface and moving into primary phase structure,namely,increase the fraction volume of TiC in the coating. All of there factors made the cracking susceptibility of the coating containing Y reduced on the premise that microhardness of the coating was increased. Microhardness of the coating without Y ranged from HV 875.6 to HV 659.8,the average microhardness was about HV 747.9. For the coating with Y,microhardness changed from HV 876.5 to HV 741.5 and the average michardness was about HV 795.3. Fracture toughness of the upper,middle,bottom and interface of the coating without Y were 6.33,8.91,11.94 and 11.93 MPa.m1/2. Fracture toughness of the similar positions of the coating with Y were 8.58,12.93,13.81,17.11 MPa.m1/2,respectively. The coating with Y presented higher microhardness and fracture toughness in comparison with that without Y. Obviously,the addition of Y had a very positive effect on the microstructure and mechanical properties of the coatings.展开更多
Ni-P-nano Al2O3 composite coatings were deposited by electroless plating,and their microstructures were observed by SEM（scanning electron microscope）.The microhardness and the wear resistance of the Ni-P-nano Al2O3 ...Ni-P-nano Al2O3 composite coatings were deposited by electroless plating,and their microstructures were observed by SEM（scanning electron microscope）.The microhardness and the wear resistance of the Ni-P-nano Al2O3 composite coatings were measured using microhardness tester and block-on-ring tribometer,respectively,and the comparison with those of Ni-P coatings or Ni-P-micro Al2O3 coating was given.The influences of aging temperature on their hardness and wear resistance were analyzed.The results showed that the nano Al2O3 particles were distributed uniformly in the Ni-P-Al2O3 coatings.Among three kinds of Ni-P based coatings,the hardness and wear resistance of Ni-P-nano Al2O3 coatings were largest,and the maximum values could be obtained at 400 ℃.This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the Ni-P coatings.展开更多
Poor corrosion resistance is a serious drawback of Mg alloys, restricting their practical applications. Coating is one of the effective techniques for improvement in the poor corrosion resistance. In this paper, the c...Poor corrosion resistance is a serious drawback of Mg alloys, restricting their practical applications. Coating is one of the effective techniques for improvement in the poor corrosion resistance. In this paper, the coating processes for Mg alloys so far developed are reviewed. Among several processes, the coating processes based on mechanical energy, including metal forming, are attractive because the corrosion resistance and formability of Mg alloys are simultaneously improved.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
基金This work was supported by National Natural Science Foundation of China(Grant No.51822505)Beijing Natural Science Foundation of China(Grant No.3182010)+1 种基金Major Scientific Research and Development Project in Jiangxi(Grant No.20173ABC28008)the National Key Research and Development Program of China(Grant No.2018YFB2000202).
文摘Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall performance for applications such as aerospace satellite parts,shafts,gears,and bushings.The addition of functional fillers can overcome the limitations of single-polymer coatings and extend the service life of the coatings by providing a combination of low friction,high wear resistance,high load bearing,high temperature resistance,and high adhesion.This paper compares the heat resistance,and the tribological and mechanical properties of common polymer matrices,as well as the categories of functional fillers that improve the coating performance.Applicable scopes,process parameters,advantages,and limitations of the preparation methods of polymer coatings are discussed in detail.The tribological properties of the composite coatings with different matrices and fillers are compared,and the lubrication mechanisms are analyzed.Fillers reduce friction by promoting the formation of transfer films or liquid shear films.Improvement of the mechanical properties of the composite coatings with fillers of different morphologies is described in terms of strengthening and toughening mechanisms,including a stress transfer mechanism,shear yielding,crack bridging,and interfacial debonding.The test and enhancement methods for the adhesion properties between the coating and substrate are discussed.The coating adhesion can be enhanced through mechanical treatment,chemical treatment,and energy treatment of the substrate.Finally,we propose the design strategies for high-performance polymer composite coating systems adapted to specific operating conditions,and the limitations of current polymer composite coating research are identified.
基金Project supported by the National Natural Science Foundation of China (51002093)the Shanghai Science and Technology Development Foun-dation, China (08QA14035)+2 种基金the Special Foundation of the Shanghai Education Commission for Nano-Materials Research, China (0852nm01400)the Crucial Project of the Shanghai Science and Technology Commission, China (08520513400)the Shanghai Leading Academic Discipline Project, China (J51402)
文摘Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with different morphologies,were investigated by X-ray diffractometer （XRD）,scanning electron microscopy （SEM） and electron probe micro analyzer （EPMA）. In addition,the effects of the addition of Y on mechanical properties （in terms of microhardness and the cracking susceptibility） were also highlighted. The results showed that the coatings were composed of α-Ti cellular dendrites,coarse needle-shaped TiB phase and an eutectic in which a large number of needle-shaped TiB whiskers and a few equiaxial TiC particles were uniformly embedded. Y was not stable and was transformed into Y2O3 during laser cladding. The addition of Y could refine the microstructure of the coating by hastening the spheroidization of primary phase structure. Moreover,it could also decrease the activity of carbon and prevent solute atoms from traversing the interface and moving into primary phase structure,namely,increase the fraction volume of TiC in the coating. All of there factors made the cracking susceptibility of the coating containing Y reduced on the premise that microhardness of the coating was increased. Microhardness of the coating without Y ranged from HV 875.6 to HV 659.8,the average microhardness was about HV 747.9. For the coating with Y,microhardness changed from HV 876.5 to HV 741.5 and the average michardness was about HV 795.3. Fracture toughness of the upper,middle,bottom and interface of the coating without Y were 6.33,8.91,11.94 and 11.93 MPa.m1/2. Fracture toughness of the similar positions of the coating with Y were 8.58,12.93,13.81,17.11 MPa.m1/2,respectively. The coating with Y presented higher microhardness and fracture toughness in comparison with that without Y. Obviously,the addition of Y had a very positive effect on the microstructure and mechanical properties of the coatings.
基金Item Sponsored by Jiangsu Natural Science Foundation of China(04KJB430013)Jiangsu Key Laboratory of Friction Wear Opening Foundation
文摘Ni-P-nano Al2O3 composite coatings were deposited by electroless plating,and their microstructures were observed by SEM（scanning electron microscope）.The microhardness and the wear resistance of the Ni-P-nano Al2O3 composite coatings were measured using microhardness tester and block-on-ring tribometer,respectively,and the comparison with those of Ni-P coatings or Ni-P-micro Al2O3 coating was given.The influences of aging temperature on their hardness and wear resistance were analyzed.The results showed that the nano Al2O3 particles were distributed uniformly in the Ni-P-Al2O3 coatings.Among three kinds of Ni-P based coatings,the hardness and wear resistance of Ni-P-nano Al2O3 coatings were largest,and the maximum values could be obtained at 400 ℃.This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the Ni-P coatings.
文摘Poor corrosion resistance is a serious drawback of Mg alloys, restricting their practical applications. Coating is one of the effective techniques for improvement in the poor corrosion resistance. In this paper, the coating processes for Mg alloys so far developed are reviewed. Among several processes, the coating processes based on mechanical energy, including metal forming, are attractive because the corrosion resistance and formability of Mg alloys are simultaneously improved.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
