Fiber Laser Cladding of WS2 + Cr on SS316 Substrate and its Characterization

In the present study, continuous wave fiber laser of 400W capacity with CNC controller is used for the cladding operation. SS316 +WS2+Cr powder mixture is taken as clad materials and SS316 of 5 mm thick plate as substrate materials. A homogeneous powder mixture is pasted over the substrate surface and laser beam is scanned by imparting motion to the XY table to get required cross-section area of the clad surface. By adjusting the (±) z–axis of working table the required size of spot diameter (divergence of laser beam) is obtained. For getting the required scan cross-section area, a CNC programmed was built with the help of SINUMERIK 828D SIEMENS controller. A gas chamber made of perpesx sheet having quartz window with different gas purging facility is used to creating required working environment. The laser beam is passed through a quartz window and strike on the surface of the powder layer. Various input process parameters were consider during the experiment such as laser power: 100-200 W, scanning speed: 500-1000 mm/min, % v/v composition of WS2: 5-15 and % v/v composition of Cr: 10 considered as variable process parameters and laser spot diameter: 0.4 mm, hatching gap: 0.2 mm, powder layer thickness: 0.7 mm. The prepared clad specimens were cut with the help of wire-EDM machine for characterization purpose. Then the sectioned specimens were polished using emery paper of different grit size followed by diamond paste polishing to get mirror finishing. Field emission scanning electron microscope (FESEM) (Model: Supra 55, Make: Zeiss, Germany) was used to study the microstructure and to do the elemental analysis. X- Ray diffraction (XRD) technique was used for phase analysis. The diffraction angle (2θ) was kept in the range of 20°-120° to detect the range of chemical compounds formed during the laser cladding process. From XRD analysis, it is can be observed that different intermetallic compounds were formed during laser cladding operation such as WS2, FeS2, FeS, CrS. The micro-hardness of the sectioned surface was measured along the clad depth using a Vickers micro hardness tester (Model: Economet VH-1 MD, Make: Chennai Metco, India). The dry sliding wear behaviour of the clad samples was analysed using a pin on disk tribometer (Make-DOCUM, India, Model: TR 201LE). The wear tests were conducted at an angular speed of 500 rpm at a radial distance of 60 mm. A dead load of 3kgf was maintained during the test for a period of 10 minutes