Microstructures And Properties Of Light Metal-ceramic Composites Manufactured By Laser Melting Deposition

Titanium alloy is suitable for the aerospace and shipbuilding industries owing to its low density and excellent corrosion resistance,which can reduce the weight of aircraft parts,showing the wide application prospect.Laser cladding（LC）technology can be used to manufacture advanced composites on the surface of metal materials via high-energy laser beam.Laser melting deposition（LMD）technology makes use of the basic principle of LC and rapid prototyping manufacturing,it takes alloy powders as the raw material,uses high-energy laser as the energy source,and melts the pre-melted alloy powders according to the predetermined processing path.Furthermore,lots of Ti in the titanium alloys can enter in to the puddle due to dilution effect during a LMD process,which can reinforce the properties of light alloy materials.Currently,the environmental requirements for material use in many fields are becoming more severe,the parts should be working for a long time under the action of extremely harsh environments,especially in the oil,aviation,shipbuilding and other industrial fields.Lots of the failure of these parts is caused by corrosion or sliding,so these parts are required to have the excellent surface performance.The wear resistance of titanium alloy is relative poor,limiting its application.For example,turbine blade made of titanium alloys can be worn by air during the high-speed rotation,which significantly decreases its service life to a certain extent.TiB₂ is proper for the LMD fields to produce ceramic reinforced composites owing to its high hardness also the well corrosion resistance;FeCrBSi amorphous alloys can strength to properties of materials,which can be ascribed to the excellent corrosion and wear performance;the microstructure of the manufactured composites can be refined with Cu-added;monolayer grahpene oxide sheets（MGOSs）have good mechanical properties,belonging to the advanced nano-materials.In this study,FrCrBSi-TiB₂-Cu-MGOSs composites were produced on the TC4 titanium alloys’surfaces by means of a LMD technique,reinforcing the properties of substrates.The temperature distribution field during LMD process was simulated by the SYSWELD software,preliminarily determining the parameters.The research was split into three parts:the impact of TiB₂ on the LMD composites’microstructures and surface properties was analyzed in the first part,the FeCrBSi-TiB₂ ceramic composites were produced via LMD（laser power 1000 W,scanning speed 10 mm/s）and then were characterized.Besides,the microstructure evolution and performance strengthening mechanism of the composites were analyzed under the action of TiB₂,showing that the microstructure of the FeCrBSi composites were composed mainly of martensite and austenite,also the defects were produced;the highest micro-hardness of the composites was848 HV_0.2,which was about 2.5 times of that of a substrate.TiB₂-added led needle and bulk microstructures to be produced in the composites,also the number of the needle precipitates increased with the rise of TiB₂.Massive fine needle precipitates were produced in the85wt%FeCrBSi-15wt%TiB₂ composites,which can be attributed to the release of B from TiB₂under the action of high temperature.Meanwhile,lots of Ti in the substrate entered into puddle,which increased the Ti content,favoring the needle TiB to be formed;the highest micro-hardness of the composites was 1297 HV_0.2,which was about 3.8 times of that of a substrate.The mechanism of the formation of defects in the LMD composites was mainly researched in the second part,indicating that the pores were favored to be formed in the FeCrBSi-TiB₂-Cu composites under the parameters of the laser power 1000 W and the scanning speed 10 mm/s,which can be ascribed to the short existence of puddle where the gas did not have enough time to escape from.When the scanning speed was dropped to 5 mm/s,the heat dissipation of the puddle was slow also the brittleness of the ceramic was high,leading the micro-crack to be produced in such fabricated composites.The microstructure and properties of the composites were improved by proper content of Cu-added.In the third part,the effect of MGOSs on the properties and microstructure of the FeCrBSi-TiB₂-Cu LMD composites were investigated,indicating that when MGOSs were located above the LMD FeCrBSi-TiB₂-Cu pre-placed layer,the MGOSs zone free of the defects was produced.Nevertheless,the pores and micro-crack were produced in the LMD fusion zone,decreasing the properties to a certain extent.When MGOSs were located below the FeCrBSi-TiB₂-Cu pre-placed coating,lots of the needle-shape precipitates with disorderly growth and relatively uniform distribution were produced.The surface property tests of both mentioned MGOSs reinforced composites were carried out.The test results showed that when MGOSs were located below the FeCrBSi-TiB₂-Cu pre-placed coating,the micro-hardness of such LMD composites was high,the corrosion performance and wear resistance of the composites were improved.This research can offer the vital theoretical significance and application value for promoting the lightweight structure in the aviation,energy power also other industrial fields.