Direct laser deposition of 410L stainless steel for surface enhancement of ASTM A36 steel

• Main Author: Guo, Yibo
• Other Authors: Zhou Wei
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/157890
• Institution: Nanyang Technological University

Direct laser deposition (DLD) is a promising technology for improvement of surface property, researchers have been performing many related studies. ASTM A36 steel is a widely applied steel for its economical and mechanical superiority. But this steel cannot undergo severe corrosion and large impact, so improving the surface properties is necessary. 410L stainless steel contains certain percentage of Cr, has outstanding corrosion resistance, hardness, ductility and high-temperature oxidation resistance. In this dissertation, 410L stainless steel powders were deposited on the surface of A36 steel. Different parameters, i.e., laser power, scanning speed and powder flow rate, were set to compare and help to select the best parameters. With optical and scanning electron microscopes, observed the morphology and microstructure of samples. Enhancement on surface hardness was measured by microhardness tests. The results point out that DLD produced three kinds of bond. For zero dilution ratio, the bond type is brazing; for samples with small molten pool depths are brazing and fusion bond type; with a large depth of molten pool, the bond type is fusion. DLD also has significant effect on microstructure evolution, thus influences the microhardness values. Laser and powder parameters act on the dilution ratio and cause phase transformation in deposit part and HAZ. Widmanstatten structure was found in fusion bond type deposition, and lath martensite appeared in HAZ. Hardness of the deposit part and HAZ are higher than substrate. The highest microhardness of the deposit part can reach 434.5 HV.