Study On Laser Cladding Fe-based Anti-wear Coatings On The Middle Chute In Scraper Conveyor

Scraper conveyor is the core equipment of mechanized coal mining,which undertakes the important tasks of coal transportation,shearer operation guidance and hydraulic support.The middle chute,the key part of the scraper conveyor,will continue to be affected by the scraper,scraper chain and coal in the operation of the violent friction,becoming the most serious wear parts of the scraper conveyor.The wear failure of the middle chute often results in frequent failures of the scraper conveyor,shortened life and other supporting equipment can not work normally,thus reducing the production efficiency and safety of the coal mine.Therefore,it is of great economic benefit and social value to study the wear resistance of the middle chute in scraper conveyor.Surface strengthening technology is a general term of the method to make products meet the needs of various working conditions and prolong their service life through physical,chemical,mechanical and other means.In recent years,with the development and application of lasers,laser cladding technology is a new surface strengthening technology developed after thermal spraying,surfacing,plasma cladding and other traditional technologies.Owing to the advantages of high efficiency,low cost,little damage to the matrix,high machining accuracy and the improvement of the hardness and wear resistance of mechanical parts,laser cladding technology has a broad application prospect in surface strengthening of mechanical parts.In this paper,the middle chute in scraper conveyor is taken as the research object.Through the design of cladding material system,laser cladding Fe-based anti-wear coatings on the middle chute can improve the surface properties of the middle chute.Main results of this study are as follows:（1）To solve the problem of easy wear of middle chute,the laser cladding surface strengthening of middle chute is studied.The Fe60 alloy powder is used as the cladding material.Firstly,the microstructure of laser cladding single-track Fe-based anti-wear coating on the middle chute is studied.Secondly,the effect of the overlapping rate on the formability of laser multi-track overlapping cladding on the middle chute is studied and the overlapping rate is optimized.Finally,the microhardness and wear resistance of the Fe-based anti-wear coating on the middle chute are studied.Results show that the Fe-based anti-wear coating on the middle chute has the compact structure without metallurgical defects such as cracks and pores,and forms a firm metallurgical bonding with the middle chute.When multi-track overlapping laser cladding is carried out on the surface of the middle chute,the overlapping rate of 50%is the optimal parameter for the Fe-based anti-wear coating with high thickness and good surface smoothness.The Fe-based anti-wear coating on the surface of the middle chute has higher hardness than the middle chute,and has higher wear resistance under the same friction conditions.The wear mechanism of the middle chute is severe adhesion wear and abrasive wear,while the wear mechanism of the middle chute changes to abrasive wear after the Fe-based anti-wear coating is produced on the middle chute by laser cladding.（2）Considering the poor abrasion resistance of the Fe-based anti-wear coating on the surface of the middle chute,laser cladding WC reinforced Fe-based anti-wear coatings on the middle chute to strengthen middle chute.Effects of amount and particle size of WC on formability,microstructure,microhardness,crack-sensitivity and wear resistance of Fe-based anti-wear coatings on the middle chute are studied.Results show that the wear resistance of Fe-based anti-wear coatings on the middle chute is significantly improved with the addition of WC,especially when the amount of WC is 20wt.%,the abrasion resistance of the Fe-based anti-wear coating on the middle chute are excellent,but the addition of WC will have the high crack sensitivity in Fe-based anti-wear coatings on the middle chute.By reducing the particle size of WC,the wear resistance of Fe-based anti-wear coatings on the middle chute is not only further improved,but also can effectively reduce the crack-sensitivity.（3）WC reinforced Fe-based anti-wear coatings on the middle chute doped with Ce O₂ are produced by laser cladding,and the microstructure and properties of Fe-based anti-wear coatings on the middle chute doped with Ce O₂ are studied.Results show that the dilution rate of Fe-based anti-wear coatings on the middle chute is decreased with the addition of Ce O₂.For Fe-based anti-wear coatings on the middle chute,the doping of Ce O₂ can also refine the microstructure,improve the uniformity of the microstructure and increase the microhardness and wear resistance.When the doping amount of Ce O₂ is 2.0wt.%,the modification effect of it is excellent.Furthermore,the doping of Ce O₂ increases the crack-sensitivity of Fe-based anti-wear coatings on the middle chute.（4）Considering the problem of poor toughness and high crack sensitivity of WC reinforced Fe-based anti-wear coatings on the middle chute,laser cladding Nb,Ti elements reinforced Fe-based anti-wear coatings on the middle chute to strengthen middle chute due to the characteristics of Nb and Ti elements in laser cladding.The microstructure,microhardness,toughness and wear resistance of Fe-based anti-wear coatings reinforced with Nb and Ti elements alone and compound are studied.Results show that the introduction of Nb and Ti can improve the toughness of Fe-based anti-wear coatings on the middle chute,but obviously decrease the wear resistance.The toughness and wear resistance of Fe-base wear-resistant coating reinforced by Nb and Ti elements are better than those reinforced by Nb and Ti elements alone,especially when the atomic ratio of Ti:Nb is 1:1,the strengthening effect of Nb and Ti elements is the best.The wear resistance of the middle chute is enhanced by laser cladding Nb and Ti elements reinforced Fe-based anti-wear coating on the middle chute,which is difficult to meet the requirements of wear resistance service conditions of the middle chute.（5）In order to improve the wear resistance and toughness of Fe-based anti-wear coatings on the middle chute,laser cladding WC,Nb and Ti reinforced Fe-based anti-wear coatings on the middle chute to strengthen the middle chute.The formability,microstructure,microhardness,crack sensitivity and wear resistance of WC,Nb and Ti reinforced Fe-based anti-wear coatings on the middle chute are studied.Results show that WC,Nb and Ti reinforced Fe-based anti-wear coatings on the middle chute has excellent formability,uniform microstructure and low crack-sensitivity.When the contents of WC,Nb and Ti are 20wt.%,2.72wt.%and 5.28wt.%,respectively,WC,Nb and Ti reinforced Fe-based anti-wear coatings on the middle chute without cracks,pores and other metallurgical defects show the bidirectional improvement in the toughness and wear resistance due to the second phase dispersion strengthening of in-situ（Ti,Nb,W）C particles.The results can effectively solve the important bottleneck problem that restricts the development of laser cladding technology in the field of surface repair and strengthening of the middle chute.