Wear Characteristic Analysis And Wear Resistant Technique Study Of Soil-engaging Component

China is a great agricultural country,there is an enormous usage amount for agricultural machinery products.However,more than 70%agricultural machinery products depend on import for the lower stability,reliability and durability of domestic agricultural products than that of abroad.This status in China isn't matching the name of manufacturing power.Among them,low abrasive resistance of critical wearproof component is the key element.Statistically,the failure probability of agricultural machinery increased about 50%due to the failure of critical wearproof component.During the farming,soil-engaging components,such as harrow disk,plough shovel share,subsoiler and rotary blade and so on,broked off the field operation for the abrasion failure of key wearproof parts.In addition,the repair and replacement of those parts also consumed time.Those shortcomings decreased the farming efficiency of agricultural machinery greatly.Therefore,it is very significant for improving the performance,quality and developmental level of agricultural machinery in China that studying the wearing characteristic,contributing factor and laws,wear resistance methods.The experiment of cultivated land and soil composition were measured and analyzed in this dissertation.The results showed that the size and amount of particles in soil were the principle factors which caused the abrasion of soil-engaging component.The major wear forms of the soil-engaging components were studied and analyzed,and came to a conclusion that abrasive wear and fatigue wear were the major wear forms.We studied the abrasion mechanism and influence factors of agricultural machinery soil-engaging components through several kinds of soil particles.The results indicated that the wear resistance of soil-engaging component can be improved by increase their hardness.According to techniques for improving the abrasive resistance of soil-engaging components domestic and overseas,three methods were chosen to research,"boronizing and isothermal quenching process","plasma spray welding" and "surfacing",which could improve the abrasive resistance of soil-engaging components,and revealed the wear resistance properties and wear mechanism of the materials obtained through the methods mentioned above from the microcosmic point of view.And then,the wear-resisting property and economy evaluation of the three methods mentioned above and wear resistance materials get form them were studied through field experiments,and the evaluation index of relative wear resistance value were given,as follow:(1)Boronizing and isothermal quenching process were proposed on the surface of 65Mn successively.The results showed that typical hard-surface and toughening-core microstructures was obtained after the treatment of two processes of 65Mn.Surface of boride layer was characterized by high hardness(about HV 1400)and good wear resistance.There were lower bainite with good strength and toughness in the core of boronized layer.The main phase of boronized layer was transformed from FeB to Fe2B after isothermal quenching.With the phase change,the brittleness decreased rapidly,and the hardness and wear resistance reduced slightly,but the hardness of treated 65Mn was larger than that of ordinary 65Mn(415-540HV).(2)Ni-based alloy composite WC particle was chosen as the powder in plasma spray welding process.Using orthogonal optimum design,optimum technology parameters for plasma spray welding of soil-engaging component were obtained:spray welding currents I=55A,spray welding distance S=14mm,spray welding speed V=35mm/min,feeding speed Q=25g/min and the addition of WC particles was 45%.Soil-engaging components were treated by plasma spray welding according the aforementioned optimum technology parameters,the results showed that the quality of spraying layer was improved obviously and the hardness also improved.(3)Using the surfacing technology,a hardfacing layer was prepared on the parts that easy to wear of plough shovel share.The surfacing layer had the features of clear grain boundary,compact and continuous organization and good metallurgical bonding with substrate.Quadratic regression equations of hardness were built according to three important parameters,surfacing speed,current and powder spraying amount.The primary and secondary sequence of factors that affected the hardness is determined by ANOVA analysis.(4)Wear properties of four kinds of 65Mn plough shovel,no treated,treated by boronizing and isothermal quenching process,plasma spray welding and surfacing,were tested by actual field tillage,and contrast tests of wear law also were tested,respectively.The results showed that the wear resistance of plough shovel made by different methods mentioned above in turn were plasma spray welding surfacing and boronizing and isothermal quenching.(5)The relationship between improving wear resistance of soil-engaging components and economy were studied.The concept of relative wear resistance cost performance coefficient was put forward for the first time,the evaluation index also be completed.Three kinds of technology to improve wear resistance of soil-engaging component were evaluated according the index.