Effect of Preliminary Laser Surface Treatment on Mechanical Properties of Diffusion Welded Joints of Fe–Ni Alloy

Abstract

Experimental studies of the effect of preliminary laser pulsed surface treatment on the mechanical properties of the diffusion welding joints of Fe–Ni alloy were carried out. The alloy surfaces was treated in an inert gas (Ar) environment by a scanning beam of nanosecond laser pulses with a wavelength of 355 nm, repetition rate of 100 Hz, and scanning speed of 1 mm/s. The laser spot was 220 μm; the energy density was 2 and 3 J/cm2. The treated samples as well as the control untreated ones were placed in the same container and were diffusion bonded by hot isostatic pressing (HIP) at the temperatures of 1000 and 1160°С. The ultimate strength and elongation of weld joint materials were determined by tensile testing. It is shown that laser pulse treatment leads to improvement in both the ultimate strength and the relative elongation of the weld joints. The mechanical properties of the weld joints depend on the laser energy density. The weld joint properties can be increased by optimization of the laser treatment parameters. The best results were achieved at a laser energy density of 2 J/cm2. The ultimate strength was increased by 12% and 29% for HIP temperatures of 1160 and 1000°С respectively. The elongation values also increased from 42% for untreated samples to 51% for samples treated at the energy density of 2 J/cm2. Preliminary laser treatment of welded surfaces makes it possible to reduce the HIP temperature by 160°С and thereby reduce the power consumption during the HIP process.