激光表面熔覆SiCp/Ni-Cr-B-Si-C涂层的组织演化及其相确定

运用激光熔覆技术在ＡＩＳＩ１０４５钢表面制备了３０ｖｏｌ－％ＳｉＣｐ／Ｎｉ－Ｃｒ－Ｂ－Ｓｉ－Ｃ涂层。ＳＥＭ和ＴＥＭ观察分析表明：ＳｉＣｐ在熔覆过程中完全溶解；涂层结合区组织为共晶结构；涂层组织由初生石墨球Ｇ，分布在γ－Ｎｉ固溶体枝晶中的Ｍ２３（Ｃ，Ｂ）６细小网状树枝晶以及少量Ｎｉ＋Ｎｉ３（Ｂ，Ｓｉ）层片状共晶组成；Ｓｉ在Ｎｉ固溶体中的固溶度显著增大，高达１４．４１ｗｔ－％；Ｍ２３（Ｃ，Ｂ）６含有高密度堆垛层错；Ｎｉ３（Ｂ，Ｓｉ）相具有长周期结构。

Microstructural Evolution and Phase Identification of the Laser Surface Clad SiCp/Ni-Cr-B-Si-C Coating

The laser surface cladding technique was used to form a 30vol-% SiCp/Ni-Cr-B-Si-C composite coating on the AISI1045 steel substrate. The microstructure of the coating was investigated by SEM and TEM. SiCp had completely dissolved in the Ni based alloy during the laser processing. The bonding zone between the coating and the substrate had an eutectic structure, characterized by directional solidification and enrichment in Fe. The clad layer had a very fine microstructure which consisted of primary graphite G in the upper part of the Clad, closely spaced M23(C,B)6 dendrites in γ-Ni solid solution, and a small amount of lamellar eutectic Ni+Ni3(B,Si). TEM EDX compositional analysis showed a marked extension in solid solubility of Si in Ni solid solution because of the high cooling rate. M23(C,B)6 contains a high density of stacking faults. The microdiffraction pattern revealed a long periodicity of Ni3(B,Si).