Study on the alleviating fretting wear property of Ni-Tl-B coatings

Activation process and preparation technology of electroless plating on titanium alloy TA7 and 45 steel were studied. Both of lead nitrate as stabilizer Ni-B coating (common Ni-B coating) and thallium sulfate as stabilizer Ni-B coating (NTB coating) were prepared based on TA7 and 45# steel substrate. Surface morphology was observed with TM-1000 scanning electron microscope, and the fretting damage resistance property was tested on DELTALAB-NENE high-precision hydraulic servo fretting wear tester. The fretting test parameters were as follows: Φ40mm GCr15 ball as fretting dual pieces, room temperature 25 ± 5°C, humidity 60% ± 10%RH, dry friction, maximum displacement D=20 μ m, normal load Fn=100N, frequency f=3Hz, maximum cycles N=3000. The results showed that: friction coefficient of NTB coating was 0.13 in running-in stage, which reduced compared with substrate and common Ni-B coating respectively. Both of the alleviating fretting damage property and the surface morphology of the coating are connected with the content of thallium salt in plating solution. NTB coating has outstanding fretting damage resistance property. Application of NTB coating can prolongs the life cycle of the products and cuts the cost of reproducing significantly.