MICROSTRUCTURE EVOLUTION OF STELLITE 6+WCBY HIGH POWER LASER CLADDING
MICROSTRUCTURE EVOLUTION OF STELLITE 6+WCBY HIGH POWER LASER CLADDING
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作者：
Li Wenjin
研究了在低碳钢E24表面采用高功率CO2激光熔覆Stellite+WC的熔覆层组织演变规律，采用送粉器分别以不同的送粉速率送粉Stellite和WC。结果表明：当WC含量为0%~ 36%（体积分数）时，合金的凝固组织主要由枝晶和枝晶间共晶组成，其中WC完全熔化进入熔池，再凝固组织中含有α-Co、α-CoCr和M7 C3等多种碳化物;当WC含量为45%~ 100%时，由基体和各种花状、蝴蝶状和星星状的小面枝晶组成，其中WC大部分熔化，组织中含有再凝固WC、Co 3和各种Co-W-C/Fe-W-C复合碳化物。W在基体中的溶解最大仅为26%，但在小面枝晶中达到64.6%。在激光熔覆纯WC时发现了一种独特的组织结构，即在较大的块状小面枝晶中出现了不同成分的双色组织，内部组织中W的质量分数高达91.2%，外部组织中W的质量分数为68.1%。这种组织可能是激光熔覆快速凝固过程中周晶反应冻结的结果。
The microstructure evolution of the cladding layer formed by high power CO2 laser cladding Stellite+WC on low carbon steel E24 was investigated, the Stellite and WC powders were delivered respectively with different feeding rates by a powder feeder. Two significantly different solidification structures were found. The first is consisted of dendrites and inter-dendrite eutectics when WC content from 0% to 36%(volume fraction), in which the added WC was completely melted into the melt pool and the re-solidified structure contained a-Co, -CoCr and various carbides such as M7C3. The second is consisted of the matrix and various faceted dendrites with flowery, butterfly and star shapes when WC content from 45% to 100%, in which most of WC was melted, the microstructure contained re-solidified WC, Co3 and various Co-W-C/Fe-W-C complex carbides. The dissolution of W into the matrix was limited to maximum of about 26% but reached to 64.6% in the faceted dendrites. A unique microstructure was discovered in laser cladding pure WC, in which a double colored structure with different compositions appeared in the larger block shaped faceted dendrite, the inner structure contained W up to 91.2%(mass fraction) while its exterior contained 68.1% W. Such a structure is probably the frozen result of the peritectic reaction during laser cladding rapid solidification.