Preparation And Properties Of Ta Coating On The 3Y-TZP Surface

3Y-TZP zirconia ceramic has got a widely spread attentions due to their excellent properties such as high strength,fracture toughness,low cost,corrosion resistance,excellent cytocompatibility,fewer bacterial adhesions and osteointegration etc,providing them a good future in dental and prosthetic replacement applications.However,the low-temperature degradation(LTD)deteriorates its mechanical properties and friction properties,leading to the failure as implants at early stage.Tantalum(Ta)is a promising metal for biomedical implants or implant coatings in recent years due to the excellent corrosion resistant and bioactive in vivo and fracture toughen.However,some insufficiencies such as high cost of manufacture,and high density have limited its widespread application as a whole Ta implants.Moreover,Ta implants are hardly formed by using traditional technology due to the high melting point,restricting their further application in biomedical engineering.In this paper,Ta coatings were deposited onto 3Y-TZP surface by using double glow plasma surface alloys(DGPSA)technology.Effects of different deposition temperatures on the microstructure,phase and friction properties of these coatings were investigated.The effect of Ta coatings to limit the phase transformation of 3Y-TZP during LTD was explored.Moreover,the biocompatibility of Ta coating was evaluated.More conclusions were obtained as following:(1)The surface morphology and microstructure of Ta coatings were significantly affected by deposition temperature.When the deposition temperature is 750 ?,the Ta coating surface is composed of many small pits(the diameter is of ~ 300 nm),and each pit consists of fine grains(the size is of ~ 20-30 nm).The surface of Ta coating deposited at 800 ? is flat with the grain size of ~ 60 nm.With the increase of deposition temperature,the surface of Ta coating has clusters,and the due to the grains growing up.With the deposition temperature increased to 900 ?,the cluster diameter is of ~ 300 nm,and the grain size increases to 100-150 nm.The roughness of Ta coating deposited at 800 ? is smallest(108.27 nm),the contact angle is minimum(28.5 °)and the adhesion strength is best(91 N).(2)The friction expreriments were conducted in PBS solution.We found that the friction coefficient decreased firstly,then increased with the rise of deposition temperature.The friction coefficients of Ta coatings deposited at 750 ?,800 ?,850 ? and 900 ? are of 0.356,0.33,0.41 and 0.545,respectively.The wear mechanisms are mainly related with abrasive wear,adhesion wear and corrosion wear because Ta coatings have the good plasticity and small thickness.(3)Ta coatings can effectively inhibit the t?m phase transformation of 3YTZP.As a result,the decrease of biaxial flexural strength and the increase of roughness have been slowed down.Ta coatings show a distingushied protective effect caused by the fact that directly contact between the environment and 3YTZP surface is prevented.After aging 100 h,the monoclinic phase content of uncoated and Ta-coated specimens was 79 % and 36 %,and bending strength decreased by 42.8 % and 22.5 % respectively.(4)The biocompatibility evaluation of Ta coatings prepared on 3Y-TZP surface includes cytotoxicity/proliferation,initial cell adhesion,and cytoskeleton assembly.Although the existence of Ta coatings has a little effect on improving the biocompatibility of 3Y-TZP,the increase of roughness is beneficial to the early adhesion of cells.