柱塞表面激光熔覆铁基涂层的强韧化机理

Strengthening and toughening mechanism of laser cladding Fe-based coating on plunger surface

关键词:  柱塞  激光熔覆  铁基涂层  耐磨性  强韧化机理

Key words:  plunger  laser cladding  iron-based coating  wear resistance  strengthening and toughening mechanism

摘要:

文中在柱塞表面激光熔覆制备高硬度铁基涂层,采用SEM,XRD,EPMA和TEM等手段研究熔覆层组织特征及耐磨性,阐述其强韧化机理.结果表明,激光熔覆铁基合金涂层成形良好,无裂纹及气孔等缺陷,熔覆层与基体呈冶金结合,组织由(Ni,Fe)固溶体、(Cr,Fe)₂₃C₆碳化物和少量孪晶马氏体组成.铁基熔覆层的强化机制主要有细晶强化、固溶强化、弥散强化以及马氏体强化;熔覆层内(Ni,Fe)固溶体及细晶强化的综合作用,保证了高硬度铁基涂层的韧性.铁基熔覆层显微硬度较45钢提高4倍,最大值H_HV0.2=850 GPa;熔覆层耐磨性明显高于45钢,45钢表面出现大面积疲劳剥落,铁基熔覆层磨损面平整,磨痕很浅且少,磨损机制为轻微的磨粒磨损.

Abstract:

Iron-based coating with high hardness are prepared on the plunger surface by laser cladding technology,and the structure characteristic and wear resistance are studied by means of SEM,XRD,EPMA and TEM,and then the strengthening and toughening mechanism is presented. The results show that the laser clad Fe-based coating has good forming without cracks and pores,as well as metallurgical bonding with the matrix, which composed of (Ni,Fe) solid solution,(Cr,Fe)₂₃C₆ carbides and a little twin martensite. The strengthening and toughening mechanism is grains refinement, solid solution strengthening,dispersion strengthening and martensite strengthening. The combined effects of (Ni,Fe) solid solution and refined grains ensure the toughness of Fe-based coating. The microhardness of the coating is 4 times higher than the one of 45 steel,with the maximum value of 850HV_0.2. The resistance of laser clad coating is also higher than the one of 45 steel,and the worn surface of 45# steel is fatigue flake,which of clad coating is smooth,and the scratch is shallow,and the wear mechanism is abrasive wear.