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Surface condition, microstructure and microhardness of boronized layers produced on Vanadis-6 steel after modification by diode laser

Abstract

The paper presents the study results of surface condition, microstructure and microhardness of Vanadis-6 tool steel after diffusion boriding and laser modification by diode laser. As a result of diffusion boriding the layers consisted of two phases: FeB and Fe2B. A bright area under the continuous boronized layers was visible. This zone was probably rich in boron. As a result of laser surface modification of boronized layers, the microstructure composed of three zones: remelted zone, heat affected zone and the substrate was obtained. The microstructure of remelted zone consisted of boron-martensite eutectic. The depth of laser track (total thickness of remelted zone and heat affected zone) was dependent on laser parameters (laser beam power density and scanning laser beam velocity). The microhardness of laser remelting boronized layer in comparison with diffusion boronized layer was slightly lower. The presence of heat affected zone was advantageous, because it allowed to obtain a mild microhardness gradient between the layer and the substrate.

Open access
Tribology of nitrided-coated steel-a review

Abstract

Surface engineering such as surface treatment, coating, and surface modification are employed to increase surface hardness, minimize adhesion, and hence, to reduce friction and improve resistance to wear. To have optimal tribological performance of Physical Vapor Deposition (PVD) hard coating to the substrate materials, pretreatment of the substrate materials is always advisable to avoid plastic deformation of the substrate, which may result in eventual coating failure. The surface treatment results in hardening of the substrate and increase in load support effect. Many approaches aim to improve the adhesion of the coatings onto the substrate and nitriding is the one of the best suitable options for the same. In addition to tribological properties, nitriding leads to improved corrosion resistance. Often corrosion resistance is better than that obtainable with other surface engineering processes such as hard-chrome and nickel plating. Ability of this layer to withstand thermal stresses gives stability which extends the surface life of tools and other components exposed to heat. Most importantly, the nitrogen picked-up by the diffusion layer increases the rotating-bending fatigue strength in components. The present article reviews mainly the tribological advancement of different nitrided-coated steels based on the types of coatings, structure, and the tribo-testing parameters, in recent years.

Open access
Wear Analysis of Cemented Carbide during Turning of Cast Iron Considering Economical Machining Speed

Abstract

The purpose of this paper is to find economical machining speed during turning of grooves for piston rings with various feeds. In the first part of the paper, literature analysis concerning durability of cutting tools is presented. Next, the wear of cemented carbide cutting tools during turning of cast iron is researched. The research has been done for seven cutting tools. During conducted turning trials, angular speed has been altered from n=530rev/min to n=710rev/min and feeds from f=0.007mm/rev to f=0.105mm/rev. On the basis of Taylor’s equation, which relates cutting speed to tool life, the economical cutting speed is established with the application of two various methods.

Open access
Determination of emissivity coefficient of heat-resistant super alloys and cemented carbide

Abstract

This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples’ temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.

Open access
The influence of cooling techniques on cutting forces and surface roughness during cryogenic machining of titanium alloys

Abstract

Titanium alloys are one of the materials extensively used in the aerospace industry due to its excellent properties of high specific strength and corrosion resistance. On the other hand, they also present problems wherein titanium alloys are extremely difficult materials to machine. In addition, the cost associated with titanium machining is also high due to lower cutting velocities and shorter tool life. The main objective of this work is a comparison of different cooling techniques during cryogenic machining of titanium alloys. The analysis revealed that applied cooling technique has a significant influence on cutting force and surface roughness (Ra parameter) values. Furthermore, in all cases observed a positive influence of cryogenic machining on selected aspects after turning and milling of titanium alloys. This work can be also the starting point to the further research, related to the analysis of cutting forces and surface roughness during cryogenic machining of titanium alloys.

Open access
The influence of laser re-melting on microstructure and hardness of gas-nitrided steel

Abstract

In this paper, modification of nitrided layer by laser re-melting was presented. The nitriding process has many advantageous properties. Controlled gas nitriding was carried out on 42CrMo4 steel. As a consequence of this process, ε+γ’ compound zone and diffusion zone were produced at the surface. Next, the nitrided layer was laser remelted using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were arranged as single tracks with the use of various laser beam powers (P), ranging from 0.39 to 1.04 kW. The effects of laser beam power on the microstructure, dimensions of laser tracks and hardness profiles were analyzed. Laser treatment caused the decomposition of continuous compound zone at the surface and an increase in hardness of previously nitrided layer because of the appearance of martensite in re-melted and heat-affected zones

Open access
Laser alloying of bearing steel with boron and self-lubricating addition

Abstract

100CrMnSi6-4 bearing steel has been widely used for many applications, e.g. rolling bearings which work in difficult operating conditions. Therefore, this steel has to be characterized by special properties such as high wear resistance and high hardness. In this study laser-boriding was applied to improve these properties. Laser alloying was conducted as the two step process with two different types of alloying material: amorphous boron only and amorphous boron with addition of calcium fluoride CaF2. At first, the surface was coated with paste including alloying material. Second step of the process consisted in laser re-melting. The surface of sample, coated with the paste, was irradiated by the laser beam. In this study, TRUMPF TLF 2600 Turbo CO2 laser was used. The microstructure, microhardness and wear resistance of both laser-borided layer and laser-borided layer with the addition of calcium fluoride were investigated. The layer, alloyed with boron and CaF2, was characterized by higher wear resistance than the layer after laser boriding only.

Open access
Laser borided composite layer produced on austenitic 316L steel

Abstract

Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides) and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

Open access
Microstructure and selected properties of boronized layers produced on C45 and CT90 steels after modification by diode laser

Abstract

The paper presents the study results of macro- and microstructure, microhardness and corrosion resistance of C45 medium carbon steel and CT90 high carbon steel after diffusion boriding and laser modification by diode laser. It was found that the increase of carbon content reduced the thickness of boronized layer and caused change in their morphology. Diffusion boronized layers were composed of FeB and Fe2B iron borides. As a result of laser surface modification of these layers, the microstructure composed of three areas: remelted zone, heat affected zone (HAZ) and the substrate was obtained. Microhardness of laser remelting boronized layer in comparison with diffusion boronized layer was lower. The presence of HAZ was advantageous, because mild microhardness gradient between the layer and the substrate was assured. The specimens with laser boronized layers were characterized by better corrosion resistance than specimens without modified layer.

Open access