Incorporation of 3μm SiCp into Titanium surfaces using a 2.8kW laser beam of 186 and 373MJm−2 energy densities in a nitrogen environment

Abstract

The formation of composite layers using a 2.8 kW laser beam of 186 and 373 MJ m −2 energy densities, on commercial purity titanium surfaces preplaced with 3 m size, 1-4 vol.% SiC p powder in a 100% nitrogen environment, produced gold colour tracks. The tracks gave reflective surfaces after glazing at an energy density of 373 MJ m −2 and dull or a mixture of dull and shiny surfaces at 186 MJ m −2 energy density. Surface cracks were visible in tracks containing 1 and 2 vol.% SiC p , but none were observed in the 4 vol.% SiC p tracks glazed at both energy densities. In the track cross sections, vertical cracks were seen in the 373 MJ m −2 tracks but it was absent in 186 MJm −2 tracks. The SiC p particles completely dissolved in all the tracks processed in this investigation producing a complex and inhomogeneous microstructure of dendrites and needle particles. At the half way of the melt depth from the surface, the dendrites were larger and densely populated, especially after glazing at 373 MJ m −2 . The hardness measurement of the MMC layer recorded a wide range of hardness values which gave loops in the hardness profiles. Hardness values ranging from 700 to 1000 Hv were observed up to a melt depth of 1 mm in many tracks and the maximum surface hardness of 2250 Hv was measured in the track containing 1 vol.% SiC p and glazed at 373 MJ m −2 . The surface hardness developed 5.6-15 times the base hardness (150 Hv) depending on the dendrite population. The 3 m size SiC p produced MMC layers 1.5-2 times greater than those previously observed with 6 m SiC p . The large surface area for an equivalent volume fraction of the three micron carbide particles is considered to have a high laser coupling action and hence absorbed more heat energy to produce deeper melt depth compared to those produced using the 6 m SiC p .

Melting of multipass surface tracks in steel incorporating titanium carbide powders

“…Their formation is associated with the rapid solidification of the melt, entrapping gases which may arise from the shielding gas and also through burning off the binder used for adhering the TiC powder on to the substrate surface. 4,11,19 Pores have been reported when other melting techniques were used for surface modification work.…”

“…High energy laser and electron beam melting techniques are established means of processing such composite layers, which are reported to increase wear and corrosion resistance significantly. [1][2][3][4][5][6][7][8] However, application of these techniques is limited in practice because of the high costs of the equipment. Previous surface engineering work using the tungsten inert gas (TIG) welding torch melting technique, [9][10][11][12][13][14][15][16][17][18][19] produced either a small hemispherical volume of a modified surface, or a single melt track with a width of a few millimetres running the length of the specimen.…”

Microstructure, wear resistance and microhardness of W-particle-strengthened Ti6Al4V composite produced with laser metal deposition

“…[15][16][17] Previously, various technologies for making metalmatrix composites (MMC) of various Ti mixes were utilised. [18][19][20][21][22] LMD is viewed as a reasonable technology for this purpose. 23,24 The LMD process entails the use of the laser power that melts the top layer of a metal substrate.…”

FABRICATION OF TI/SIC SURFACE NANO-COMPOSITE LAYER BY FRICTION STIR PROCESSING

“…However, their usage is hindered in wear resistance applications due to their poor tribological properties including poor wear resistance, low hardness values and high coefficient of friction 6 . Thus, a number of surface modification techniques have been developed to fabricate surface titanium matrix composites [7][8][9] . However, the existing techniques are generally involved in surface melting and its associated solidification problems, including creation of defects, separation of particulates from the matrix due to differences of thermal expansion coefficients and formation of unwanted phases.…”