Preparation And Characterization Of Metal Thermal Protective Coating

The metals and alloys will react with the oxygen when they are exposed to high pressure in the air.The problem of oxidation and decarbonization will become more and more serious with the longer of heating time and the higher temperature.However,the metals or alloys have to be heated the high temperature to complete some processes,such as quenching,annealing,normalizing,rolling and die forging.Therefore,high temperature resistant inorganic nonmetallic materials are generally used as substrates for metal thermal processing protective coatings.However,there exist some drawbacks for inorganic nonmetallic protective coatings.For example,inorganic nonmetallic protective coatings have a low adhesion of the coating to the metal material in production and it does not have enough ability to protect the metal material at low temperature.The purpose of the text is to solve the drawbacks of the Inorganic nonmetal protective coatings,combined with the practical application requirements of hot metal working,designing organic polymer materials as the matrix,matching expansion flame retardant and inorganic flame retardant filler,and preparing metal thermal processing protective coatings.In the lower temperature period,the organic silicon resin is developed the continuous coating protecting the metal surface,while in the higher temperature,expansion flame retardant is decomposed to form a dense carbon layer which plays a role of protection.Firstly,a kind of heat working protective coating was made with epoxy resin as matrixand other additives such as intumescent flame retardant,curing agent,aluminum hydroxide,etc.The morphology and thickness of oxide layer on metal surface were observed by SEM and metallographic microscope,and the tensile properties of the coatings were tested by the universal tensile testing machine,and the thermal properties of each component were studied withthermogravimetric analysis.The results show that in 600?temperature environment,with epoxy resin and curing agent at the ratio of 3:1,curing agent and intumescent flame retardant ratio of 2:1,the coating on the metal protection effect can reach the best.With smooth metal surface,no obvious groove,it can be observed that the minimum thickness of the surface oxide layer is only 20?m by SEM.As the temperature continues to rise,the oxide layer will become thicker accordingly.After the temperature is more than 800?,the oxide layer on the metal surface falls off and the coating will lose efficacy.The TG test results showed that the epoxy resin began to decompose around the temperature of 300?,it will be almost completely decomposed at 500?.The results of mechanical properties test showed that the maximum tensile strength of the coating can reach 67 MPa,and the bonding property of the coating on the metal surface is extremely well.Secondly,because of the epoxy resin coating limiting to the surface of metal protected.heated the metal for 1 h at the constant temperature over 800?,the thickness is over 100?m,and the oxide layer is brightly and hard.The coating lost protecting action.So choosing the better performance of endure heated of the organic silicon resin,which replacing the epoxy resin and let it the substrate of paint.The epoxy resin is used to the substrate and addition the IFR,CaCO₃ and so on.Use them for the metal protection paint of organosilicon resin base.The morphology and thickness of metal surface's oxide is observed by SEM.The Tensile shear property is tested by the universal tensile testing machine.The heat property of the paint is analysed and studied by the TG.The result shows that,keeping 100g 107silicone rubber,15 g 201 silicone oil,1.5 g KH550,1 g KH560,9 g PER,5 g MOS,4 g VOS,adding 100 g CaCO₃?100 g Al?OH?₃?30 g IFR invariably at 800?.,the effect of protection of the Silicon paint is the best to the surface of metal and the surface of the metal smoothly.Oxide phenomenon hasn't happened.The SEM shows that the oxide layer is only14?m at the thinnest place.The TG analysis show that the thermal decomposition temperature can up to 320?.So compare with epoxy resin based paint.The organic silicon resin posses the higher temperature than the epoxy resin based paint.The testing result of the strength of the tensile shear show that the maximum elastic modulus of silicone based paint is 142 MPa and the mechanical properties of the coatings are excellent.At last,the organosilicon resin has crack at the high temperature.So adding the glass fiber to the organic silicon resin can improve the thermal stability.The glass fiber isn't melt at the process of heating,the action is restraining the split of organic silicon resin.Observing the morphology and thickness of the surface of metal oxide by SEM.The tensile and shear properties of the paint were tested by tensile testing machine,and the thermal properties of the paint were analyzed by TG.The result of test show that,the action of improved of glass fiber is notable at 1000?.The thickness is only 9?m.At the condition of enhance the processing temperature,the thickness of oxide is 5?m,which it is thinner than the before modification.The strength of the tensile shear is increased from 13 MPa to47 MPa.