Laser Surface Engineering

Processes and Applications

Jonathan R. Lawrence, David Waugh

• Publisher: Woodhead Publishing
• Year: 2014
• eBook ISBN: 9781782420798
• Topic: Technology & Engineering
• Subtopic: Industrial Engineering
• Index: Technology & Engineering

Lasers can alter the surface composition and properties of materials in a highly controllable way, which makes them efficient and cost-effective tools for surface engineering. This book provides an overview of the different techniques, the laser-material interactions and the advantages and disadvantages for different applications. Part one looks at laser heat treatment, part two covers laser additive manufacturing such as laser-enhanced electroplating, and part three discusses laser micromachining, structuring and surface modification. Chemical and biological applications of laser surface engineering are explored in part four, including ways to improve the surface corrosion properties of metals. - Provides an overview of thermal surface treatments using lasers, including the treatment of steels, light metal alloys, polycrystalline silicon and technical ceramics - Addresses the development of new metallic materials, innovations in laser cladding and direct metal deposition, and the fabrication of tuneable micro- and nano-scale surface structures - Chapters also cover laser structuring, surface modification, and the chemical and biological applications of laser surface engineering

Part One

Thermal surface treatments using lasers

1

Structures, properties and development trends of laser-surface-treated hot-work steels, light metal alloys and polycrystalline silicon

L.A. Dobrzański^1,2; T. Tański¹; A.D. Dobrzańska-Danikiewicz¹; E. Jonda¹; M. Bonek¹; A. Drygała^{1 1} Silesian University of Technology, Gliwice, Poland
² The Institute of Advanced Manufacturing Technology, Cracow, Poland

Abstract

Several examples have been chosen for presentation from a broad array of laser surface treatment technologies currently researched into and used in industry and the examples are distinguished by their extensive possibilities of future and current applications, especially in the tooling, automotive, and power industry. A newly developed methodology has been employed in order to make an objectivized assessment of the relevant laser surface treatment technologies. Contextual matrices and roadmaps and technology information sheets allowing for the mainly qualitative comparisons of the individual technologies according to harmonized criteria were created as a result of employing the methodology.

Keywords

Laser surface treatment

Hot-work tool steels

Light metals

Polycrystalline silicon

Development perspectives

1.1 Introduction

Several examples of application have been chosen for presentation from a broad array of laser surface treatment technologies currently researched into and used in industry and the examples are distinguished by their extensive possibilities for future and current applications, especially in the tooling, automotive, and power industry.

Hot-work tool steels still represent a widely used group of tool materials that are especially interesting for their advantageous quality-to-price relation and very good functional properties. Heat treatment, heat and chemical treatment, and heat and mechanical treatment have been used traditionally to improve their properties. The laser treatment of surface layers of hot-work alloy tool steels, including laser remelting and/or alloying to enhance their functional properties, especially hardness and wear resistance, is an attractive alternative. The remelted zone (RZ) and the heat-affected zone (HAZ) are created as a result of the laser remelting of steels in the surface layer with their thickness increasing proportionally to the power of the laser used for remelting. If steel remelting is carried out without using carbide powders, then a noticeable, yet slight improvement in the properties of the surface layers of the steels examined is seen as compared to their respective properties obtained in conventional heat treatment, depending on the laser beam power used for remelting. If alloying additives such as different kinds of carbide powders, for example, niobium (NbC), tantalum (TaC), titanium (TiC), vanadium (VC), and tungsten (WC), are introduced into the liquid metal pool, a marked improvement of mechanical and functional properties of the examined steels is seen as compared to those undergoing conventional heat treatment as well as laser remelting without using the powders.

The surface laser treatment of light metal alloys, that is, casting magnesium and aluminum alloys, consisting of cladding carbide particles (TiC, WC, VC, SiC) or oxide particles (Al₂O₃) into their surface has an advantageous effect on their quality and structure and brings a promising enhancement of mechanical and functional properties of the examined material, especially hardness, and is largely dependent on laser power and a concentration of alloy elements. The laser cladding of carbide and oxide powders influences the fragmentation of the structure within the entire range of laser power, and the varied grain size in the specific zones of the investigated alloys’ surface layer. Two zones occur in surface layers: a RZ and a HAZ with their characteristic values (e.g., layer thickness) dependant upon the laser power used and the carbide or oxide powders cladded.

The laser surface treatment of polycrystalline, the crystallization process of which, preceding the production of photovoltaic cells is much faster and cheaper than the crystallization of its monocrystalline form, consists of the texturization of its surface to reduce light reflectivity and ensure reabsorption of a photon already reflected from the surface. Laser texturization involves creating parallel or intersecting grooves on the entire surface of material. The advantage of this technology is that it is contact-free and selective; its drawback is the damages done to the layer in the place where a laser beam operates and in the contiguous area. Therefore, the laser-treated material must next undergo chemical etching to reveal the proper texture in the form of parallel grooves in two directions perpendicular to each other.

All the laser surface treatment technologies mentioned here have very extensive developmental and application prospects, therefore, further scientific and research efforts to develop and improve them are justified. A newly developed methodology of the computer-integrated prediction of materials surface engineering development has thus been employed to make an objective evaluation of the particular technologies; to determine the positive and negative factors conditioning their future development; and to identify the applicable, recommended action strategy. Contextual matrices, road maps, and technology information sheets allowing for the quantitative and qualitative comparisons of the individual technologies according to harmonized materials science and technological and economic criteria are the outcome of the investigations conducted [1–3].

1.2 Laser treatment of hot-work alloy tool steels

A primary aim of the laser remelting of material surface layers is to formulate their structure and properties, which takes place in the process of creating a chemically homogenous, fine-crystalline surface layer without changing the chemical composition of the material [4–6]. Alternatively, laser alloying aims to improve the mechanical and functional properties of the material as a result of strengthening its surface layer with alloying elements from the partially dissolved particles of hard phases of carbides, oxides, or nitrides [7,8]. The following are the strengths of laser surface treatment versus other surface engineering methods: short process duration, flexibility and precision of manufacturing operations that can be performed with various materials, starting with the ones that are hard to work with through the soft ones, ending with brittle materials, and ensuring accuracy and performance of other methods applied up till now [9]. By being able to adjust accurately such process pa...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Woodhead Publishing Series in Electronic and Optical Materials
• Dedication
• Preface
• Part One: Thermal surface treatments using lasers
• Part Two: Laser additive manufacturing in surface treatment and engineering
• Part Three: Laser struturing and surface modification
• Part Four: Chemical and biological applications of laser surface engineering
• Index