Abstract
The high-velocity oxy-fuel spraying process was used to investigate and improve the surface properties of a workpiece. The research was focused on the spherical surface of a workpiece made of high-strength steel, a ball and socket assembly. After spraying with a nickel alloy, the surface was machined by milling. The coating was carried out as a process in which a very thin layer of coating of the required thickness and the required specific properties, i.e., high Vickers hardness, adhesion to the surface, wear resistance and other important characteristics, which must be respected in other machining methods, was applied to the already finished, heat-prepared metal substrate. This article deals with the milling of complex surfaces of steel substrate EN 10060 after spraying with NiCrBSi alloy. After spraying, a total of 15 milling experiments were performed in order to determine precisely the optimal cutting parameters of milling and surface adhesion, based on newly acquired prediction relations. The main presented results are new relations for the determination of optimal technological milling conditions based on the identification of adhesive sections using derived equations. The new relations were verified and also compared with the current literature in the field.
Highlights
The aim of the application of coatings created by high-velocity oxy-fuel is the modification or restoration of functional surfaces with specific properties on machine parts while reducing production and operating costs [1,2,3]
During the process of coating using the thermal spraying technology [6], the base material is not heated above 100 ◦ C, in exceptional cases, it is heated to 150 ◦ C, i.e., during the application of the coating material, there is neither deformation of the coated part nor degradation of the structure due to thermal effects on the base material
Except for the presence of Ni and Ni–Cr phases, it was observed a layer of Cr2 O3 in the thickness of a few nanometers. There is another interesting study [16] of the NiCrBSi coatings with a different extent of tungsten carbide particles prepared by the flame method on spring steel
Summary
The aim of the application of coatings created by high-velocity oxy-fuel is the modification or restoration of functional surfaces with specific properties on machine parts while reducing production and operating costs [1,2,3]. An interesting comparison was made by Houdková et al [14] They studied the mechanical properties, microstructure, wear and friction properties of thermally sprayed NiCrBSi coatings with consequent post-heat-treatment by different technologies. Except for the presence of Ni and Ni–Cr phases, it was observed a layer of Cr2 O3 in the thickness of a few nanometers There is another interesting study [16] of the NiCrBSi coatings with a different extent of tungsten carbide particles prepared by the flame method on spring steel. When verifying the above properties, it is decisive whether the tests are performed on testing machines, possibly directly under operating conditions, or on experimental equipment that only simulates the operating conditions and effects on the coating With these experimental devices, it is complicated to simulate the specific working conditions in a given device, so the results obtained when comparing different types of materials can be misleading in some cases. The presented publication was created in order to improve the surface properties of a spherical steel surface after HVOF spraying of a nickel alloy, which is subsequently machined by milling
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