【作者】 静丰羽；

【导师】 孙玉福；

【作者基本信息】 郑州大学 ， 材料工程（专业学位）， 2013， 硕士

【摘要】 磨损是煤矿机械零部件在实际工况条件下最主要的失效形式。为了提高采煤机截齿、刮板输送机中部槽的使用性能及服役寿命,根据其失效形式,本文提出采用等离子熔覆—注射B4C技术在采煤机截齿前端表面制备一层低成本、高耐磨、厚约2-4mm的B4C增强Fe基熔覆层；在中部槽易磨损工作面,按其规格不同,熔覆一定数量、厚约2-4mm的条状熔覆层。通过熔覆—注射优化试验,确定了合适的B4C注射位置和合理的工艺参数,制备出了外观良好、性能优越的含B4C陶瓷相的复合熔覆层。采用金相显微镜、扫描电镜分析了熔覆层、界面和热影响区的组织特征；测试了熔覆层洛氏硬度,并进行耐磨性试验并对磨损形貌观察,评价了熔覆层的耐磨性能。研究了熔覆层的组织及性能的关系,分析了该熔覆层的磨损机理,并进行了生产试验。结果表明：(1)影响等离子熔覆—注射B4C的工艺因素很多,且存在交互作用,经过大量试验,最终优化的等离子熔覆—注射的工艺参数为：喷嘴与基材间的高度25～28mmm；离子气流量10L/min；送粉气流量7.5L/min；熔覆电流215A；熔覆速度420mm/min;送粉量67g/min；注射量12g/min；注射角度30°；注射位置距拖尾边缘的距离2-4mm,验证性试验表明,该工艺参数满足生产要求。(2)等离子熔覆—注射B4C熔覆层表面粗糙度大,这是由于涂层的表面内部镶嵌了粒度较大的B4C陶瓷颗粒。其内部组织具有明显的快速凝固特征,整体具有细小的晶体结构。熔覆层向边缘方向表现出不同的凝固组织形态,在界面处为平面晶,然后过渡为柱状晶,熔覆层表面由于注射B4C,对熔体产生激冷作用,B4C间隙中的组织细小、均匀。(3)混配B4C的铁基熔覆材料,在熔覆加工过程中B4C的剧烈气化导致熔覆层的形貌恶化。熔覆层很薄且不平整,熔覆层表面出现大量的气孔和裂纹。B4C熔化后,元素B、C重新发生冶金反应,形成大量条块状的CrB、Fe2B、(Cr,Fe)2B和(Fe, Cr)23(C,B)6等化合物。该熔覆层具有硬而脆的特点,测量洛氏硬度时,熔覆层表面出现被压头压碎、崩块的现象。(4)在实验室中的测试,等离子熔覆—注射B4C层的表层耐磨性是基体材料Q235的50倍,是16Mn钢的41倍,是42CrMo的22倍,是不含B4C陶瓷相熔覆层的20倍,是混配B4C熔覆层的3-4倍。说明熔覆层中存在B4C陶瓷相对于提高熔覆层的耐磨性来说是十分有效。熔覆—注射B4C复合层的磨损形式主要为微观切削、犁沟,且犁沟很浅,熔覆层耐磨性十分优异。(5)经过该项技术强化后的截齿,和普通的截齿相比,在同等工况下,其使用寿命可延长3-5倍。该工艺强化加工后的中部槽,和普通的中部槽相比,在同等工况下,其使用寿命可延长5-7倍。更多还原

【Abstract】 The wear is the main failure mode for coal mining machinery during use.In order to improve the performance and service life of the middle trough of the scraper conveyor and cutting pick, by plasma cladding-injection B4C technology, high wear resistance, about2mm thickness was fabricated on the cutting pick surface, and2-4mm thick strip cladding layer was fabricated wear face in the middle slot, according to the failure form and shape of the cutting pick. Through the analysis of the process, a suitable the B4C injection position and reasonable process parameters was determined after several tests to verify. Finally a good appearance, superior performance containing B4C ceramic phase composite cladding layer was prepared.Microstructure of the coating, the interface and the heat-affected zone was examined by means of optical microscope (OM) and scanning electron microscope (SEM). Phase compositions were certified by SEM-EDS. The surface Rockwell of the coating were tested on the Rockwell hardness tester. Abrasive wear resistance test was performed to evaluate the wear-resistance property of the coating. The relationship of microstructure and properties, and the wear mechanisms of the cladding layer were studied. The results showed that:(1) The impact of plasma cladding-injection B4C process factors are many, and there were interactions, after a large number of tests ultimately optimized plasma cladding-injection process parameters:the height between the nozzle and the substrate:25-28mm; plasma gas flow.10L/min; feeding gas flow:7.5L/min; the cladding current:215A; cladding speeds:420mm/min; powder feed rate:67g/min; injection volume:12g/min; injection angle:30°; injection location away from the trailing edge distance:2～4mm, confirmatory test, the process parameters to meet production requirements.(2) Plasma cladding-the injection the B4C layer of surface roughness is large, this is due to the larger particle size of B4C ceramic particles inside of the coating. Its organization has obvious rapid solidification characteristics overall having a fine crystal structure. Different microstructure morphology appears in the cladding layer to the edge direction, at the interface plane crystal, then the transition of columnar crystals, the surface of the cladding layer due to the injection of B4C melt, B4C clearance organization also has a small, uniform features.(3) Mixed B4C Fe-based cladding materials, in the process the B4C gasification causes deterioration of the morphology of the cladding layer. Cladding layer is very thin and not flat, the surface of the cladding layer pores and cracks. In B4C melted, the elements B, C re metallurgical reaction occurs, forming a large number of blocks the CrB、Fe2B、(Cr,Fe)2B and (Fe,Cr)23(C,B)6and so on. The cladding layer has a hard and brittle characteristic, the surface of the cladding layer appears the phenomenon of collapse block crushed by the pressure head when measurement of Rockwell hardness.(4) In the laboratory test, plasma cladding-the B4C layer surface of the injection wear resistance is50times to the matrix material Q235,41times to16Mn steel,22times to42CrMo,20times to the cladding layer excluding B4C ceramic phase,3-4times to mixed B4C cladding layer. That’s to say, the B4C ceramic phase is present in the cladding layer is very effective for improving the wear resistance of the cladding layer. Cladding-injection B4C composite layer wear mainly in the form of micro cutting furrows, furrows very shallow, very excellent wear resistance of the cladding layer.(5) After the technology enhanced the middle trough of the scraper conveyor and cutting pick, used in the production performance and in the same conditions, cutting pick’s life can be extended to3-5times, the middle trough’s life may be extended to5-7times.更多还原