Study On The Technology Of Reducing The Dilution Rate Of Plasma Spray Welding

The wear resistance of materials is effectively improved by surface engineering technology.And plasma spray welding technology with a spray layer and the base metal interface for the metallurgical combination,spray width and height controllable are easy to achieve automation.However,there are some problems in plasma spray welding technology and the widespread use of plasma spray technology,which are largely influenced for the high plasma arc temperature and likely to cause spray layer dilution rate and be more sensitive process parameters.At present,the adjustment and optimization of the parameters of plasma spraying can mainly be realized by practical experience and orthogonal test method,which theirs relevant parameters are to be determined independently and to be coordinate adjusted difficultly.In order to obtain the relatively optimized combination of process parameters,a large number of process tests are often needed,which have not only a high degree of reliance on the operator,but also complexity on operation.And the method of determining the parameters is poorly reproducible.From the thermophysical properties of the material,a rapid adjustment method of welding parameters was studied to solve the problem in controlling the dilution rate and regulate process parameters of spray welding.According to the plasma spray gun,tungsten needle and transfer arc power supply of the three minimum loadable value of the initial,the transfer arc current is established.The welding rate was determined by the case of microfluidation on the surface of the substrate without powder spray.And then the formula of calculating the amount of powder is deduced from the volume thermal expansion formula before and after melting.Finally,the formula of the transfer arc current is deduced based on the energy conversion and the energy law of the plasma spray.A rapid computational method were investigated to quickly attain the appropriate parameters,such as transferred arc current,spray welding speed,and powder feeding rate,and a process parameter combination of plasma spray welding could be easily acquired.To verify this rapid computational method,a process experiment that the Ni60 a alloy powder is sprayed on the Q235 substrates has been set in plasma spray welding with different thickness of spray welding coatings.The experimental result suggests that,the spraying layer can be obtained by using the process parameters calculated by this computational method,showing good adhesion with substrates and high surface hardness,the precipitation phase is chromium compound and γ-Ni solid solution,the minimum and maximum hardness of coating surface is Hv 730 and Hv 804,respectively.The plasma spray welding process can be used for plasma spray repair process and multi-layer multi-channel spray welding process.In order to popularize the application of special surface of plasma spray,this study is of great significance.