Titanium Powder Metallurgy

Science, Technology and Applications

Ma Qian, Francis H. Froes

• Publisher: Butterworth-Heinemann
• Year: 2015
• Print ISBN:
  9780128000540
• eBook ISBN:
  9780128009109
• Topic: Technology & Engineering
• Subtopic: Mining Engineering
• Index: Technology & Engineering

Titanium Powder Metallurgy contains the most comprehensive and authoritative information for, and understanding of, all key issues of titanium powder metallurgy (Ti PM). It summarizes the past, reviews the present and discusses the future of the science and technology of Ti PM while providing the world titanium community with a unique and comprehensive book covering all important aspects of titanium powder metallurgy, including powder production, powder processing, green shape formation, consolidation, property evaluation, current industrial applications and future developments. It documents the fundamental understanding and technological developments achieved since 1937 and demonstrates why powder metallurgy now offers a cost-effective approach to the near net or net shape fabrication of titanium, titanium alloys and titanium metal matrix composites for a wide variety of industrial applications. - Provides a comprehensive and in-depth treatment of the science, technology and industrial practice of titanium powder metallurgy - Each chapter is delivered by the most knowledgeable expert on the topic, half from industry and half from academia, including several pioneers in the field, representing our current knowledge base of Ti PM. - Includes a critical review of the current key fundamental and technical issues of Ti PM. - Fills a critical knowledge gap in powder metal science and engineering and in the manufacture of titanium metal and alloys

1

A historical perspective of titanium powder metallurgy

Francis H. (Sam) Froes Consultant to the Titanium Industry, Tacoma, WA, USA

Abstract

The history of titanium powder metallurgy (PM) is reviewed from the early days of the titanium industry (late 1940s) to the present day (late 2013). The first attempts at a PM approach to fabrication of solid titanium articles were displaced as a commercial process by ingot melting techniques. The blended elemental and prealloyed (PA)/hot isostatic press (HIP) approaches were investigated in the late 1960s and early 1970s with some success but no commercial applications. The status of titanium PM was comprehensively reviewed at a landmark TMS Conference in 1980. Around 1990, some early efforts at metal injection molding (MIM) of titanium with some nonstructural parts were made. This was followed by attempts at spray deposition of titanium in the 2000s and the development of commercial MIM (including structural components), blended elemental (a high point being the qualification of parts for Boeing commercial aircraft), PA/HIP, and additive manufactured technologies. A comprehensive review of titanium PM was documented at a conference in 2012.

Keywords

titanium

historical perspective

early work

prealloyed/HIP

blended elemental

additive manufacturing

metal injection molding

spray deposition

research-based processes

1.1. Introduction

Powder metallurgy (PM) is the production, processing, and consolidation of fine particles to make a solid metal. A primary advantage of the PM approach over other methods lies in the more efficient use of material. Other advantages include greater shape flexibility and reduced processing steps.

For many years a large, well-established PM industry involving materials such as iron, copper, and nickel-based alloys has been in existence. The main driver here is cost reduction; mechanical properties play only a secondary role. During the 1980s, PM of titanium alloys was established. Cost and material savings have been the major goal, with two PM approaches, the prealloyed (PA) technique and the blended elemental (BE) method, mainly on Ti-6Al-4V, the workhorse alloy of the titanium industry.

The PA approach is typically designed to produce demanding aerospace components in which mechanical property levels (particularly fatigue behavior) need to be equivalent to those of cast and wrought ingot metallurgy. These requirements have been met with the establishment of clean powder production and handling procedures.

In contrast, titanium compacts produced by the BE method have generally not achieved the fatigue levels required for critical aerospace components because of inherent salt and porosity. These products are aimed at applications not requiring high dynamic (fatigue) properties. In the late 1980s, low-chloride start-stock became available that led to improved density and enhanced fatigue behavior. Production costs for the BE technique are lower than those for the PA technique.

This chapter reviews the history of titanium PM from the early days of the titanium industry (late 1940s) to the present day (late 2013). The early unsuccessful attempts at producing a solid article was followed by a number of years before the technique was commercialized. A landmark TMS Conference was held in 1980 followed by a gap of almost 20 years before commercialization of titanium PM techniques began to occur. At the present time, a number of approaches are poised for widespread commercialization, including metal injection molding (MIM, for structural and nonstructural components), BE (a high point being the qualification of parts for Boeing Commercial aircraft), PA/hot isostatic press (HIP), and additive manufactured technologies.

1.2. The early years (late 1940s to early 1950s)

The conversion of titanium sponge to a solid article presented very difficult engineering challenges during the early development of the titanium industry in the late 1940s. There were no facilities available at that time for melting the reactive metals without severe contamination. Liquid titanium reacts rapidly with, or dissolves, all solids, liquids, and gases except the inert gases, including argon and helium.

The first serious efforts to consolidate titanium were made by William J. Kroll, the inventor of the magnesium-reduction process bearing his name. Two basic methods were studied by Kroll, the US Bureau of Mines, and private industries. One method employed PM techniques for cold compaction and sintering. These steps were followed, in some cases, by hot or cold working to produce small amounts of metal products suitable for inspection and testing. Such products, however, were found to have serious shortcomings that could not be corrected at that time despite major efforts. Residual magnesium chloride (MgCl₂) salts entrapped within the metal particles impaired the mechanical properties and weldabi...

Table of contents

• Cover
• Title page
• Table of Contents
• Copyright
• List of contributors
• About the editors
• Preface
• 1: A historical perspective of titanium powder metallurgy
• 2: Conventional titanium powder production
• 3: Production of titanium powder by an electrolytic method and compaction of the powder
• 4: Titanium powder production via the Metalysis process
• 5: Direct titanium powder production by metallothermic processes
• 6: Research-based titanium powder metallurgy processes
• 7: Titanium powders from the hydride–dehydride process
• 8: Low-cost titanium hydride powder metallurgy
• 9: Production of titanium by the Armstrong Process®
• 10: Hydrogen sintering of titanium and its alloys
• 11: Warm compaction of titanium and titanium alloy powders
• 12: Pressureless sintering of titanium and titanium alloys: sintering densification and solute homogenization
• 13: Spark plasma sintering and hot pressing of titanium and titanium alloys
• 14: Microwave sintering of titanium and titanium alloys
• 15: Scavenging of oxygen and chlorine from powder metallurgy (PM) titanium and titanium alloys
• 16: Titanium metal matrix composites by powder metallurgy (PM) routes
• 17: Titanium alloy components manufacture from blended elemental powder and the qualification process
• 18: Fabrication of near-net-shape cost-effective titanium components by use of prealloyed powders and hot isostatic pressing
• 19: Metal injection molding of titanium
• 20: Powder-processing linkages to properties for complex titanium shapes by injection molding
• 21: Titanium sheet fabrication from powder
• 22: Cold-spray processing of titanium and titanium alloys
• 23: Thermal spray forming of titanium and its alloys
• 24: The additive manufacturing (AM) of titanium alloys
• 25: Powder-based titanium alloys: properties and selection
• 26: A realistic approach for qualification of PM applications in the aerospace industry
• 27: Powder metallurgy titanium aluminide alloys
• 28: Porous titanium structures and applications
• 29: Microstructural characterization of as-sintered titanium and titanium alloys
• 30: Future prospects for titanium powder metallurgy markets
• 31: A perspective on the future of titanium powder metallurgy
• Index