In order to improve the service life of the smoothing boots,40CrNi2Si2MoVA coatings were prepared on the substrate of the smoothing boots by four scanning methods,long side unidirectional,short side unidirectional,long side bi-directional,and short side bi-directional.The macroscopic morphology,microstructure,hardness and wear resistance of the coatings were studied,and the comprehensive service life of the smoothing boots with different coatings was evaluated by on-machine experiments.The results show that the clad layers by four scanning methods have good metallurgical bonding with the substrate,and there are no obvious pores and cracks on the surface.The microstructure of the clad layer mainly consists of cellular crystals,dendrites,columnar crystals and equiaxed crystals.When using the long-sided unidirectional scanning mode,the clad layer has a finer and denser grain size and the best quality organization.The microhardness of the clad layer by unidirectional scanning method is higher than that by bidirectional scanning method.The wear resistance of the clad layer by short-sided unidirectional scanning method has obvious advantages.The experiments on the machine show that the 40CrNi2Si2MoVA coating has a great improvement on the service life of the smoothing boots.