Advanced Materials & Processes

NOV-DEC 2013

Covers developments in engineering materials selection, processing, fabrication, testing/characterization, materials engineering trends, and emerging technologies, industrial and consumer applications, as well as business and management trends

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HTPRO LASER SURFACE HEAT TREATMENT AND MODIFICATION LASER SURFACE MODIFICATION TECHNIQUES PROVIDE A NEW PATH TO ENHANCE A MATERIAL'S RESISTANCE TO THE DETRIMENTAL EFFECTS OF CORROSION, ABRASION, AND WEAR. 9 Hitesh D. Vora* and Narendra B. Dahotre, FASM* University of North Texas, Denton Researchers are continually looking for ways to enhance materials performance by developing both new materials and processing methods including nontraditional fabrication/processing/manufacturing techniques, such as laser surface modification (LSM). Lasers have emerged as a versatile tool in a wide variety of industrial applications[1]. Newer, more efficient lasers (especially fiber lasers) along with advancements in automation techniques, enable expanded use of this technology as a costeffective processing and manufacturing tool to enhance materials surface and subsurface performance[2], beyond conventional applications such as drilling, cutting, and welding. LSM plays a key role in improving many materials properties as shown in Fig. 1[1, 3–5]. This article provides a brief overview of LSM techniques and their use in a wide variety of engineering applications at multidimensional scales (nano to meso) to meet ever increasing industrial demands. Fig. 1 — Applications of laser surface modification techniques. based computational simulation and experimental studies. The authors adopted integrated computational and experimental approaches (Fig. 2) to optimize LSM parameters based on targeted values for a few key attributes, such as hardness, microstructure, dilution, and corrosion/wear properties[6, 7]. LSM enhances surface properties either by altering surface metallurgy or surface chemistry, or by The effectiveness of LSM can be further improved using integrated computational methodologies such as finite-element modeling (FEM) and optimization techniques, such as analysis of variance Fig. 2 — Schematic of integrated computational and experimental approach for laser surface modification. (ANOVA). These integrated approaches overcome difficulties associated with insitu measurement (e.g., temperature, melt-pool geometry, and concentration adding a surface layer of strategic mategradient) encountered during laser prorials to meet application requirements cessing, because heating/melting/vaporwithout losing the physical ization occur in a small confined zone characteristics of the for a very short time. In addition, LSM is bulk material, as shown influenced by many factors such as laser in Fig. 3[2, 3]. processing parameters (e.g., power, beam scanning speed, and overlap beAltering surface metallurgy tween successive laser tracks), materials In the past, strengthening thermal properties, heat transfer phemechanisms (e.g., solid-solution hardnomena, and convection-induced mixening, grain refinement, and solid-state ing in the molten pool. These factors can phase transformation) were developed be addressed by using optimization apby altering surface metallurgy to yield Fig. 3 — Array of laser surface modification proaches, such as regression analyses higher surface strength, hardness, techniques with examples of and ANOVA, in conjunction with FEMtoughness, and ductility for both cryscorresponding processes. *Member of ASM International and ASM Heat Treating Society ADVANCED MATERIALS & PROCESSES • NOVEMBER-DECEMBER 2013 45

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