Preparation And Properties Of W-mo Modification Coating On γ-TiAl By Double Glow Plasma Surface Alloying Technology

Alloys based on γ-TiAl offer an attractive combination of low density,high melting point and exhibit good corrosion resistance performance.As a consequence of these attributes,γ-TiAl is very desirable for applications in advanced aerospace and automobile engines.However,the practical uses of γ-TiAl remains limited due to its poor oxidation resistance and wear resistance.In this research,W-Mo modification layer was manufactured by double glow plasma surface alloying technology.That could effectively improve the surface performance of γ-TiAl.The Mo modification layer and W modification layer were also manufactured for comparison.The most suitable process parameters obtained from orthogonal experiment.The optimum parameters a as below: holding time 3h,substrate voltage 500 V,source voltage 850,working pressure 35 Pa,and distance between the source and substrate 20 mm.The W-Mo modification layer had a thickness of 9μm and well bonded to the γ-TiAl.The coating consisted of pure W and Mo.The surface hardness of W-Mo modification layer was enhanced to 853.2HV0.1,which was 2.8 times that of γ-TiAl.The nano-hardness was 10.337 GPa and the elasticity modulus was 282 GPa.O₂xidation experiments were carried out to study the oxidation resistance of samples at 750℃,850℃and 950℃.In 750℃ and 850℃,oxidation film of W-Mo modification layer was compact and well bonded to the γ-TiAl.The oxidation product is MoO₂,MoO₂₃,WO₂₃,Al₂O₂₃ and TiO₂.In 900℃,the oxidation surface was covered of globular grains and the interior was flocculated grain.The oxidation product is MoO₂₃,WO₂₃,Al₂O₂₃ and TiO₂.The oxidation weight increase of W-Mo modification layer was minimum,which was 4.6324mg/cm2.That was about 21.47% of γ-TiAl,which could effectively protected g-TiAl against oxidation.Reciprocating friction resistance experiments were carried out to study the wear resistance in different load and speed.The results instructed that W-Mo modification layer combined with the lubrication action of Mo modification layer and the high wear resistance of W modification layer.The friction coefficient of W-Mo modification layer was minimum,which was 0.45.The wear volume of W-Mo modification layer was 0.0051mm3 and the wear rate was 0.1487×10-4·mm3·m^-1,which was 8.32% of γ-TiAl.The wear mechanism of W-Mo modification layer was abrasive wear.W-Mo modification layer could effectively improve the wear resistance of g-TiAl.