Effect of laser power and deposition environment on the microstructure and properties of direct laser metal-deposited 12CrNi2 steel

Direct laser metal deposition was used for preparing blocks of steel 12CrNi2 using four different laser powers under two different deposition environments including atmospheric environment and Ar-protected chamber.The results showed that microstructures and mechanical properties were significantly affected by different laser powers.Increasing laser power and deposition in Ar chamber will lead to a decrease in the quantity and size of the voids,which brings more elongation to the samples.Bainitic microstructure was replaced by Widmanstatten ferrite and pearlite,and the amount of proeutectoid ferrite increased with increasing laser power.Moreover,microstructures of previous layers were completely altered in high laser power.Excessive heat accumulation by using high heat input can produce equiaxed ferritic grains with the pearlites in previously deposited layers.Hardness of deposited samples increased from the bottom layer toward the top layer.By using a diode laser with a spot diameter size of 2 mm,the 900-W laser power is suitable for producing crack-and void-free samples.However,post-deposition heat treatment is necessary for obtaining homogeneous desired microstructure and grain size in the manufactured samples.