Effects Of QPQ And Galvanization Composite Processing On Mechanical Properties And Corrosion Resistance Of Hight Strength Fastence

QPQ technology is one of new technology for metal surface strengthening. It will not pollute the environment. It has anti-corrosion and heat treatment effect. It had been developed successfully in resent years,offering superior surface properties such as high hardness, good wear-resistance,improved fatigue resistance and very good corrosion resistance for the treated components. Processing specimen deformation is small. It is energy saving .In this article ,QPQ and galvanized composite processing was applied for surface modified of 35CrMo. Galvanization technology has a lot of research . We mainly study of QPQ carbonitriding layer organization influence . The treated surface microstructure was observed by using Metallographic microscope,meanwhile the thickness and the quclity of the compound-layer were analyzed.Effect of different process parameters on corrosion resistance for QPQ treated work-pieces was researched. Galvanization is very small On the mechanics properties. We mainly study QPQ process parameters on the influence of mechanical properties . Temperature on mechanical properties of infiltration nitrogen worst affected . We design the 500℃, 550℃,630℃, 580℃.We match permeability nitrogen time, mass fraction of cyanate root according to QPQ process parameters on the effect of carbonitriding layer organization . Above600℃QPQ is deep QPQ. Deep QPQ have a middle layer. Cooling way affecte intermediate organizations. We adopt water-cooled, air cold, with furnace cold . Through the tensile tests and impact tests ,the tensile strength ,yield strength,elongation and impact energy were attained.We analyzed the relations of processing parametre and mechanical properties. The corrosion resistance of treated steel 35CrMo was investigated throung electrochemical tests and salt spray tests.The results indicated that: Tensile strength, yield strength, elongation and reduction of mechanical properties of 500℃processing sample is990Mpa , 815 Mpa , 15.2% ,55.13%and112 J.cm-2 which is much more perfect than the other. The compound layer is brittle fracture. The fracture types of the middle layer is related to the cooling product,ratio and distribution. The diffusion layer is intergranular fracture.The corrosion resistance of composite processing sample is far stronger than single QPQ processing and galvanizing. Corrosion potential of composite layers decrease with increase of Cl- and temperature:this exhibits corrosion resistance of composite layers decrease with increase of Cl- and temperature;corrosion potential of composite layers remove to cathode in the acidity NaCl solution comparing with alkaline solution.corrosion potential of composite layers remove to cathode in the alkaline NaCl solution comparing with neutrality solution. This showed corrosion resistance of composite layers was preferable in the neutrality environment, the second in the alkaline environment, the third in the acidity environment.