Basic Study On QPQ Treatment Of Steel For New Gun Barrel

The life of the barrels in our country's current firearms equipment can‘t meet the needs of modern military training and combat capabilities.We usually need to backup gun barrels to meet the use of firearms,which brings challenges to cost,firearms mobility,logistics and other aspects.At the same time,The life of the barrel has an impact on the development of automatic weapons along the high initial speed and high precision.The improvement of barrel life can be studied from barrel material,optimization of gun,cartridge and charge matching design and manufacturing process,and barrel bore surface treatment technology.In view of the problems of ablative wear caused by inherent cracks and environmental pollution caused by Cr⁶⁺in the chromium plating surface treatment of gun barrel.In this paper,the new QPQ salt bath composite technology was used to process and analyze the new gun barrel material.The research will provide some reference value for the improvement of the accuracy and life of the barrel,the reliability of the equipment,the survivability of the battlefield and the adaptability to the environment.The main contents of this study are as follows:(1)The most suitable salt bath permeating agent was selected from a large number of previous experiments.A certain amount of lanthanum chloride,yttrium chloride and yttrium carbonate rare earth accelerator compounds were selected to test the accelerator effect of samples in the early stage.The best yttrium rare earth carbonate compounds were selected according to the thickness of the compound layer,keeping the nitriding temperature,nitriding time and cyanate content unchanged.(2)The thickness,microstructure,microhardness,brittleness and phase morphology of the permeable layer were analyzed.The salt-bath treated samples exhibited better performance at 550?,reaching a compound layer thickness of 68?m and a total permeable layer thickness of 108?m.The compound layer is dense and uniform.From the surface to the inside,it is oxidized film,loose layer,compound layer and diffusion layer.The microhardness test showed that the surface hardness of 490? and 550? increased by 2.75 times and 2.89 times,respectively.The brittleness tests show that the brittleness of the samples treated at490?is level 1,and that at 550?is level 2.The phases of the samples treated by salt bath at 490? and 550? are the same,and the phases content of the samples treated at 550?are higher,which are?(Fe_2-3N),(?)'(Fe₄N),Fe₃O₄and Cr N.The diffraction peak deviates to a small Angle and becomes wider,which is due to the increase of lattice constant and grain refinement caused by nitriding.(3)Electrochemical workstation and high temperature friction and wear testing machine were used to analyze the corrosion resistance and friction and wear properties of samples treated by salt bath at 490? and 550? respectively.It was found that the corrosion potential Ecorr and corrosion current density Icorr of the treated samples decreased,which was due to the precipitation of Cr N,which inhibited the formation of passivation film on the metal surface,leading to the decrease of the corrosion resistance of the samples.In the wear test,the higher the wear temperature is,the better the wear performance is.The samples treated at 490?have better wear performance at normal temperature,and the samples treated at 550? have better wear performance at high temperature.The wear mechanism of untreated samples is mainly adhesion and abrasive wear at normal temperature,and oxidation wear at high temperature.The wear mechanisms of samples treated at 490?and 550?are mainly adhesion and oxidation wear at normal and high temperatures.