Formation of Wear-Resistant Chromium-Nickel Coating with Extra High Thermal Stability by Combined Laser-and-Heat Treatment

Abstract

The influence of heat impact at 200 -1050°C on the structure, phase composition, microhardness and tribological characteristics due to sliding over a NiCrBSi fixed abrasive (corundum) is studied for a PG-10N-01 coating deposited by a gas-powder laser method. A combined laser-and-heat treatment is suggested, which yields a heat-resistant chromium-nickel coating containing a thermally stable high-strength wear-resistant skeleton of coarse carbides and chromium borides.

Eddy-current testing of fatigue degradation in additionally heat-treated gas powder laser clad NiCrBSi coating under contact fatigue loading

“…This suggests the possibility of improving the quality of the coatings by additional heat treatment, this being supported by the data found in the literature [2,3]. It was first shown in [3] that high-temperature stabilization annealing at a temperature of 1000 to 1050 °C sharply increases the hardness and tribological properties of the Ni-18.2Cr-3.3B-4.2Si coating to the levels corresponding to the characteristics of this coating after laser cladding, or even exceeds them. Simultaneously, the thus formed coating is heat-stable and, consequently, retains high values of hardness and abrasive wear resistance when heated up to the temperature of stabilization annealing.…”

“…During laser cladding of nickel-chromium coatings, rapid cooling (up to 10 3 -10 4 °C/s) of the clad metal through heat conduction [1] results in the formation of metastable structural states characterized by the presence of a supersaturated solid solution and fairly dispersed particles of strengthening phases [2]. This suggests the possibility of improving the quality of the coatings by additional heat treatment, this being supported by the data found in the literature [2,3]. It was first shown in [3] that high-temperature stabilization annealing at a temperature of 1000 to 1050 °C sharply increases the hardness and tribological properties of the Ni-18.2Cr-3.3B-4.2Si coating to the levels corresponding to the characteristics of this coating after laser cladding, or even exceeds them.…”

“…However, additional heat treatment of the clad coating may also cause its embrittlement. For example, 1050 °C annealing of nickel-based alloy specimens prepared by direct laser deposition [4], as in [3], increased abrasive wear resistance of the clad specimens. Simultaneously, the strength characteristics of the heat-treated specimen decreased 5 times under conditions of static tension for three-point bending, its plasticity being 2.5 times as low as that of clad specimen.…”

Thermal stability of a laser-clad NiCrBSi coating hardened by frictional finishing

“…A considerable thermal softening of a NiCrBSi coating at temperature ranging between 900 and 950 С was reported in [8], where a new phenomenon of an increase in the hardness and wear resistance of a laser coating due to high-temperature (1000 С and higher) annealing forming a wear-resistant framework from large particles of strengthening phases (carbides, borides) was also demonstrated. The above-mentioned large particles precipitate under cooling (from the annealing temperature) from metastable oversaturated solid solutions formed when metal is rapidly cooled in the course of laser cladding.…”

“…The discovered phenomenon is used to develop a combined method including laser cladding and stabilizing annealing [9]. The method provides producing Ni-based coatings with an especially high level of heat resistance [8].…”