Laser coating (laser cladding) is a useful method to produce metal matrix composite (MMC) coatings. The selection of the metallic matrix can be done on the base of the intended application and environment, whereas the additional wear resistance improvement is provided by mixing various carbides with the metallic matrix. In the present work, various types of MMC coatings were prepared by laser coating methods. The coatings consisted of vanadium, tungsten, titanium and chromium carbide hard phases mixed with metallic tool steel M2, Stellite 21, NiCrBSi-alloy and Inconel 625. Different levels of carbide contents were used. The abrasion resistance of the MMC coatings has been tested using a rubber-wheel abrasion apparatus. The wear surfaces were examined and the microstructures of MMC coatings were analysed in order to determine microstructures and carbide dissolution. The best abrasion results were achieved by the correct choice of carbide for each matrix material.

Microstructure and properties of hard and wear resistant MMC coatings deposited by laser cladding

https://profdoc.um.ac.ir/articles/a/1055852.pdf

Welding processes for wear resistant overlays

Laser cladding is a process whereby a new layer of material is deposited on a substrate by laser fusion of blown powders or pre-placed powder coatings. Multiple layers can be deposited to form shapes with complex geometry. This manufacturing process has been used for material surface property modification and for the repair and manufacture of three-dimensional components. Laser cladding has attracted extensive research over the past 30 years. Over 2000 research papers have been published in journals and international conferences. Research in laser cladding covers many scientific issues, including processing techniques, physical and chemical properties of deposited materials and clad—substrate interfaces, microstructure and phases, rapid solidification phenomena, modelling and simulation, and systems engineering and applications. This article, focusing on the rapid heating/cooling processes and material response, summarizes the state of the art on two fundamental scientific aspects: rapid solidific...

Laser surface cladding: The state of the art and challenges

Abrasive wear performance and microstructure of laser clad WC/Ni layers

In the present study, laser cladding of AISI H13 tool steel powder has been undertaken on hardened and tempered AISI H13 tool steel components using a 6 kW fiber coupled diode laser both in continuous wave and pulsed mode with coaxial powder feeder to explore the possibility of reclamation/refurbishment of large AISI H13 tool steel components. Laser parameters in terms of laser power, processing speed and powder feed rate have been optimized to achieve acceptable clad-substrate integrity with optimum deposition height and width without any surface cracks and porosity. A detailed study of the effect of post-cladding heat treatment (both by laser assisted surface heating and conventional tempering at 550 °C) on the microstructure, phase aggregate, crystallite size, micro-strain and residual stress was carried out. Subsequently, the microhardness of the clad zone was evaluated. Pulsed laser cladding (heat input controlled) with 50 Hz frequency and 50% duty cycle with 10 ms ON-time developed a microstructure comprising martensite, retained austenite and mixed carbides. The maximum improvement in hardness (considered as a convenient index of strengthening) by laser cladding reached up to 650 VHN, which is about 45% higher than the hardness of hardened and tempered substrates. Post-cladding tempering at 550 °C for 2 h led to the development of uniform microstructure without fine carbide precipitated along grain boundaries or inter-dendritic regions taking the hardness to 600–650 VHN level. Laser reheating (tempering) of the clad zone with a 1000 W laser power showed a more refined microstructure with maximum hardness up to 680–700 VHN. Residual stress, developed on the surface after laser cladding, was compressive in nature and measured higher in magnitude after pulsed laser cladding. Magnitude of this residual compressive stress marginally decreased after post-cladding tempering either by conventional or laser assisted route. Thus, the novelty of the present study lies in the continuous or pulsed mode laser cladding assisted reclamation of AISI H13 hot working dies with similar composition powder, followed up with conventional or laser assisted tempering, leading to the development of about 45% higher hardness (than as hardened and tempered conditions) and retention of residual compressive stress on the surface after cladding.

Effect of laser parameters on microstructure and hardness of laser clad and tempered AISI H13 tool steel

Composites of three different tungsten carbide powders and two matrix alloys of the Co–Cr–C and Ni–B–Si type were cladded on to mild steel using a 6kW CO2 laser. The effects of parameter variation,...

R. C. Gassmann

Papers

Laser cladding with (WC+W2C)/Co–Cr–C and (WC+W2C)/Ni–B–Si composites for enhanced abrasive wear resistance