M. Cadenas

Tribological properties of laser clad Stellite 6 coatings on steel substrates

Abstract The laser cladding of diesel engine exhaust valves is an emerging technology that provides excellent results in terms of the wear and corrosion resistance of the repaired materials. This work focuses on the deposition by laser cladding of Stellite 6 alloy coatings on two different base materials: an AISI 1045 carbon steel and an AISI 304 stainless steel. Following a process optimisation criterion, several of the fundamental laser treatment parameters were varied in order to obtain defect-free coatings with good adherence and minimal dilution. The metallographic structure of the clad material, irrespective of the substrate used, consists of a typical dendritic microstructure in a solid solution of Co. The mechanical strength of the layers was analysed by measuring HV0·1 microhardness and sliding wear behaviour. Laser coatings achieved hardness greater than 500 HV0·1, and presented excellent dry sliding wear behaviour, with a dimensional wear coefficient k one and a half orders of magnitude lower than that of the substrates. A combined oxidation and abrasion mechanism dominated the wear of the Stellite 6 layers, while in the case of AISI 1045 steel substrate, the wear was caused mainly by a surface oxidation mechanism. For the AISI 304 steel, the wear resulted from a combined adhesion, abrasion and plastic deformation mechanism.

NiCrBSi coatings textured by Nd-YAG laser

This work presents and discusses the influence of Nd-YAG laser parameters on the texturing of a low laser absorptivity NiCrBSi coating obtained by diode laser cladding. In order to obtain statistical significance, different kinds of design of experiments were considered, choosing a central composite inscribed design as the best according to the number of factors and required runs. In the first stage, a diode laser is used to obtain the NiCrBSi coating and in the second stage an Nd-YAG laser is used to generate surface texturing. Finally, results are observed with a confocal microscope, obtaining diameter and depth of the dimples and statistically studied plotting Pareto charts and response surfaces. The study led to the following conclusions: higher energies and spot diameters generate dimples with larger diameters; low energies and shorter pulse duration involves greater diameters; at high energies diameters remain nearly constant versus pulse duration; at higher energies, shorter pulse durations show greater depths; and at low energies depth remains almost constant versus pulse duration.

Microstructure of NiCrBSi Laser Cladding Coatings Textured by Nd-YAG Laser

The use of texturing as a surface treatment that improves the tribological behavior is widespread in industrial and scientific fields, it is used in internal combustion engines [1], in biomechanical applications [2], in manufacturing processes [3] and in a full range of different applications. When texturing is carried out at low energy levels, the material melts superficially in a process governed by convection and thermocapillarity phenomena [4], whereas at high energy levels the reaction of the material could lead to its sudden vaporization [5] and local melting.Copyright

Laser Cladding Of Tungsten Carbide Powder

Cermets ofWC-Co as materials for coatings to resist wear could be considered of frequent use in industry. However, the behaviour of those coatings depends on the deposition technique used: welding, plasma-spray, laser cladding, etc.. This paper presents the study of 83% WC-Co coatings on the surface of AISI 1043 steel. A CO: laser was used to melt the powder and a minimal part of the substrate. The comparison of the characteristics of laser cladding coatings with plasma-spray coatings, both of them obtained with the cermet, shows in the former a very important decrease of the porosity, a higher coating hardness and a very good adherence layer-substrate. In consequence, its wear behaviour also presents differences. The wear evaluation is presented by PV diagrams and the wear rate measures. Block-on-ring in lineal contact test were done with laser cladded layers and plasma sprayed layers versus a tempered and quenched AISI 1043 steel. Tests were done under limit lubrication conditions for different sliding speeds. PV diagrams results show that for sliding speeds over 0.4 m/s. the plasma-spray coatings support higher contact pressures than the laser cladded layers. However to lower speeds, these have a better behaviour. On the other hand, it could be observed that laser cladding coating has a wear rate approximately a 34% lower than the plasma-spray one.

Effect Of Laser Treatment On Tungsten CarbideCoatings

A CO2 laser operating in continuous mode has been employed to refuse tungsten carbide coatings plasma sprayed onto a substrate of steel, in order to reduce their porosity. Wear tests block-on-ring type and hardness estimations have been carried out for both treated and untreated coatings. The results show an increase in the wear resistance and hardness of the coatings after laser treatment.

Wear Behaviour Of Laser Clad WC-Co Powder

This paper shows laser cladding using WC-Co on low carbon steel and the microslructural characteristics of the resulting coating. It also analyses wear behaviour for different load and velocity conditions through a P-V diagram .

Position Problem in Assur’s Groups with Revolute Pairs

This paper shows a methodology to solve the position problem in Assur’s groups of any class exclusively using revolute pairs. The methodology is based on the elimination of a rigid bar of the Assur’s group which you want to get the position. The resulting 1-DOF linkage can be modeled with one group of primary elements and one or more Assur’s groups of class lower than the original group. Then, an optimization problem consisted in finding the optimal value of the DOF for which the pairs, joined by the eliminated rigid bar, are separated by the original distance, is posed. This methodology also allows unequivocally choose the assembly mode to obtain the original Assur’s group.

Improvement Of AISI1045 And AISI1020 By Laser Surface Hardening

The traditional tempering methods induce strong stresses in the tried elements. It is necessary however for numerous industrial applications to maintain the properties of the material in the interior of the bulk at the same time as an elevated superficial hardness. Laser tempering achieves notable increments of hardness whilst modification of the surface is kept to a minimum. The control of the parameters that participate in the process, combined with the characteristics of the material, enable a specific hard layer to be obtained. Two steels were treated, AISI 1045 and AISI 1020, with a laser of CO? of 1700 W of capacity. In this paper, we reveal the working method, and the influence of the different parameters of the laser machining and material. As a result of the process, a superficial layer of more than 500 HV of hardness in the AISI 1020 was obtained. The treatment of AISI 1045 has provided layers of more than 1mm of 500 HV and layers of 0.6 mm thickness over 700 H)/.

Laser Surface Treatment Of A1203 Coatings PlasmaSprayed

Laser surface treatment of A12O3 plasma sprayed coatings is studied in this paper from an experimental viewpoint. A CO2 laser operating in continuous mode is used to refuse a thick layer of 0,3 mm thickness. The changes in microstructure, microhardness and adherence caused by the laser treatment allows a better wear behaviour of this coating after laser treatment. The initial porosity of A12O3 plasma sprayed coating is considerably reduced after laser treatment. However in this case few vertical cracks appear. This fact can be reduced by using a preheating of the specimens to decrease the thermal effects of the laser treatment.