MOLDS WEAR AND ITS ECONOMIC CONSEQUENCES
GLOSSARY
WEAR The removal of material from surfaces in contact and in relative movement.
FRICTION The force generated between two surfaces in contact and in relative motion.
ABRASION The process of material removal from loose particles or asperities on an opposing surface that are
moving against the abraded surface.
EROSION The process of material removal from particles that impact against a surface.
INTRODUCTION
In the world of manufacturing, molds play a pivotal role in shaping products across a multitude of industries. From
automotive components to food packaging, molds are indispensable tools that help create precise and uniform
products. However, like any other equipment, molds are not immune to the wear and tear of time and usage.
Mold wear is a silent but significant issue that often goes unnoticed until its economic consequences become
apparent. In this article, we will explore the economic losses, increased self-cost of products, equipment
downtime, and other ramifications associated with mold wear.
MAIN TYPES OF WEAR
Figure 1, as depicted in Gee & Neale’s work from 2002, illustrates the primary modes of wear. Concerning
hardmetals, the significant categories include abrasion, erosion, and sliding wear, with a more comprehensive
examination of the first two available in this chapter. Impact and thermal fatigue also assume significance in some
specific scenarios. It’s noteworthy that, in many instances, multiple types of wear concurrently influence the wear
damage, rendering its interpretation complex and challenging. This confluence often results in an accelerated
removal rate compared to when individual wear types act independently. Encouragingly, recent strides in sample
preparation and high-resolution imaging techniques hold the promise of supplying additional quantitative insights
into wear mechanisms, which are anticipated to materialize over the next decade.
Substantial progress has already been achieved, particularly through the application of orientation imaging studies
(like electron backscattered diffraction or EBSD) on deformed materials near tool surfaces, which is contributing
significantly to our understanding, as indicated by Gee & Mingard in 2009. Furthermore, single-point abrasion tests
are gaining popularity as a means of employing these high-resolution characterization techniques to gain an indepth comprehension of microstructural wear processes that prove challenging to interpret in multifaceted
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multibody abrasion systems. Consequently, this chapter also delves into crucial aspects of this innovative
approach.
It’s pertinent to acknowledge that, in many wear scenarios, a synergy can develop between the environment and
the tool/workpiece system. This synergy can amplify wear rates to a degree greater than what might be projected
by considering each mechanism in isolation. Frequently, this amplification occurs due to the formation of
exceptionally thin tribofilms, which pose considerable challenges in terms of characterization, particularly within
sliding wear systems. Additionally, wear processes involve the exposure of surface layers to elevated
temperatures. The extent of this temperature elevation and its distribution through the material’s depth arguably
represents one of the least comprehended aspects when endeavoring to fathom wear processes in their entirety.
Both of these facets of tool wear behavior unquestionably warrant further dedicated research efforts.
THE UNSEEN COSTS OF MOLD WEAR:
• Increased Scrap and Rework Costs: As molds deteriorate, they lose their precision and ability to produce
high-quality parts. This can result in an increase in defective products, which must either be scrapped or
undergo costly rework to meet quality standards. These additional expenses can significantly impact a
company’s bottom line.
• Reduced Productivity: Mold wear can slow down production lines, leading to decreased output and lost
revenue. When molds no longer function optimally, it takes more time to produce each unit, leading to
inefficiencies and increased labor costs.
• Equipment Downtime: When molds reach a point of excessive wear, they often require maintenance or
even complete replacement. This downtime can be expensive, as it halts production and may necessitate
costly repairs or the procurement of new molds.
• Increased Self-Cost of Products: Mold wear directly affects the cost per unit of the products being
manufactured. When molds produce more defective parts or require longer production times, the selfcost of each product increases, eating into profit margins.
• Quality Control and Reputation: Molds that are not maintained properly or replaced in a timely manner
can compromise product quality. This can damage a company’s reputation, leading to decreased
customer trust and potential loss of market share.
PREVENTING AND MITIGATING MOLD WEAR
While mold wear is inevitable to some extent, there are several steps manufacturers can take to minimize its
economic impact:
• Regular Maintenance: Implement a rigorous maintenance schedule to inspect and maintain molds. This
includes cleaning, lubricating, and replacing worn components.
• Quality Materials: Use high-quality materials for molds, as they tend to wear less and have a longer
lifespan.
• Monitoring and Data Analysis: Employ sensors and monitoring systems to track mold performance. This
data can help predict when maintenance or replacement is necessary.
• Training and Skill Development: Train staff in mold maintenance and troubleshooting to detect wearrelated issues early on.
• Invest in Spare Molds: Keep spare molds on hand to minimize downtime when replacements are needed.
• Utilize Advanced Technologies: Explore advanced technologies like 3D printing for molds, which can offer
cost-effective and rapid mold replacement options.
THE TUNGSTEN CARBIDE ADVANTAGE
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Tungsten carbide, often referred to as hardmetal, is a remarkable material that has gained prominence in various
industrial applications, including moldmaking. Its unique properties make it an ideal choice for combating mold
wear:
1. Exceptional Hardness: Tungsten carbide ranks among the hardest materials available,
significantly surpassing the hardness of common mold materials like steel. This exceptional
hardness ensures that molds can withstand prolonged use without undergoing significant wear.
Cemented carbide exhibits an impressive room temperature hardness range of 86 to 93 HRA,
equivalent to 69 to 81 HRC.
2. When compared to high-speed tool steel, cemented carbide tools permit cutting speeds that are
4 to 7 times faster, resulting in a service life 5 to 80 times longer. This exceptional hardness
allows cemented carbide to cut materials with a hardness of up to 50HRC.
3. High Strength and Elastic Modulus:
Cemented carbide boasts a remarkable compressive strength of up to 6000MPa and an elastic
modulus ranging from 4 to 7 × 10^5MPa, surpassing high-speed steel.
However, it should be noted that its bending strength is relatively lower, typically ranging from
1000 to 3000MPa.
4. High Temperature Resistance: Tungsten carbide retains its strength and hardness at elevated
temperatures. Its high hardness is retained at elevated temperatures, typically between 900 to
1000°C, thereby ensuring excellent wear resistance.
5. Wear Resistance: Tungsten carbide’s wear resistance is unmatched, which means molds made
from this material can endure extensive use without deteriorating. This leads to longer mold
lifespans and reduced downtime for replacements.
6. Chemical Inertness: Tungsten carbide is highly resistant to chemical corrosion, ensuring that it
maintains its integrity even when exposed to aggressive materials or corrosive environments.
7. Precision Machining: Tungsten carbide can be precisely machined to create intricate mold
designs, allowing for the production of complex and high-precision components.
8. Minimal Coefficient of Linear Expansion: When in operation, cemented carbide maintains the
stability of its shape and dimensions due to its low coefficient of linear expansion.
COMMON TYPES OF CEMENTED CARBIDE
Cemented carbides can be categorized into three primary groups based on their composition and properties, with
tungsten-cobalt and tungsten-titanium-cobalt alloys being the most prevalent in industrial use.
• TUNGSTEN-COBALT CEMENTED CARBIDES: Predominantly comprised of tungsten carbide (WC) and
cobalt (Co), denoted by the designation YG, followed by the cobalt content percentage. For instance, YG6
designates a tungsten-cobalt cemented carbide containing 6% cobalt (wCo = 6%), with the tungsten
carbide content represented as wWC = 94%.
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• TUNGSTEN-TITANIUM-COBALT CEMENTED CARBIDES: Consist primarily of tungsten carbide (WC),
titanium carbide (TiC), and cobalt (Co). Identified by the label YT, followed by the percentage of titanium
carbide content (wTiC).
• TUNGSTEN-TITANIUM-TANTALUM (NIOBIUM) CEMENTED CARBIDES: Also referred to as universal
hard alloys, these alloys comprise tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC),
or niobium carbide (NbC), in combination with cobalt (Co). Recognized by the YW label, followed by an
ordinal number.
APPLICATIONS OF CEMENTED CARBIDE
TOOL MATERIALS
Cemented carbide is a prevalent choice for tool materials, enabling the production of turning tools, milling tools,
planers, drills, and more.
Its usage varies based on the specific composition, making tungsten and cobalt carbides suitable for processing
non-ferrous metals and non-metallic materials, while tungsten-titanium-cobalt alloys are ideal for ferrous metals,
especially steel.
The carbide content, specifically the cobalt percentage, determines suitability for roughing or finishing tasks.
Cemented carbide tools significantly outperform other materials, particularly when machining challenging
materials like stainless steel.
MOLD MATERIALS
Cemented carbide is extensively employed in cold drawing dies, cold punching dies, cold extrusion dies, and cold
piercing dies.
Measuring Tools and Wear-Resistant Components:
Cemented carbide is utilized for the inlaying of abrasive surfaces and components in measuring instruments,
precision grinding machine bearings, guide plates, centerless grinding machine guide bars, lathe centers, and other
wear-resistant parts.
In summary, cemented carbide stands as a formidable material known for its outstanding wear resistance, making
it an indispensable element in various industrial applications, particularly those requiring high precision, durability,
and longevity.
REFRACTORY PRESS MOLD LININGS
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Press mold liners are primarily used for molding refractory bricks. Refractory product molds, also known as dies for
refractory bricks, serve as templates for shaping these specialized products. The mold’s shape and geometric
dimensions are meticulously designed to mirror the desired final product. Its structure comprises a mold frame, a
backing plate, and a template. The formwork is subjected to substantial forming pressure from the brick press,
resulting in significant friction between the brick and the formwork. Consequently, the template’s surface is prone
to wear and tear. Generally, if wear reaches a depth of 0.3-0.4mm, it is considered unfit for further use. Therefore,
the template must exhibit exceptional wear resistance, often achieved through the use of cemented carbide,
among other materials.
PRODUCT DEVELOPMENT HISTORY
FIRST GENERATION: The primary materials employed were modified cast iron, A3 steel, mild steel, and 45# steel.
Surface hardness and wear resistance were improved through heat treatment, achieving a hardness of HRC60-64.
This laid the foundation for creating press molds. The advantage of this approach lies in its cost-effectiveness and
speedy delivery. However, it is hampered by a relatively short lifespan measured in hundreds of cycles.
SECOND GENERATION: The main materials shifted to tool steel and ultra-high carbon steel. While this approach
increased costs, it also extended the mold’s lifespan beyond that of normal materials. Nevertheless, it still fell short
of meeting the market’s demand for high efficiency.
THIRD GENERATION: Tungsten carbide emerged as the material of choice. It involves brazing carbide tiles onto
steel backing plates. There are several methods within this generation:
• Brazing the entire carbide plates onto the mold, which, unfortunately, renders the carbide susceptible to
breakage during use.
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• Brazing the entire parts with carbide tiles. This method offers better performance, allowing for
approximately 9,400 cycles. However, it still doesn’t meet customer requirements and may experience
cracks during usage.
• Brazing carbide tiles onto smaller steel backing plates, accompanied by thread holes for convenient
installation. This approach significantly enhances performance, enabling more than 15,000 cycles.
Below are images of the press mold liners produced by our company. This design is favored by our customers, and
the liner’s performance aligns with customer expectations. This advantage greatly extends the refractory brick
mold’s service life, reduces the frequency of mold replacement, and significantly enhances the efficiency of
refractory brick pressing.
Due to variations in refractory brick materials, our skilled craftsmen in Xiamen use different grades of cemented
carbide to produce brazing plates, ensuring a minimum hardness of 91.5HRA.
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ECONOMIC BENEFITS OF TUNGSTEN CARBIDE MOLDS
Utilizing tungsten carbide molds offers several economic advantages to manufacturers:
• Extended Mold Lifespan: Tungsten carbide molds have a significantly longer service life compared to
traditional mold materials, reducing the frequency of mold replacements and associated downtime.
• Lower Scrap and Rework Costs: The enhanced wear resistance of tungsten carbide molds results in fewer
defects and scrap parts, minimizing the need for costly rework and reducing waste.
• Improved Product Quality: Tungsten carbide molds maintain their precision and surface finish over
extended periods, ensuring consistent product quality and reducing the risk of defects.
• Enhanced Production Efficiency: Longer mold lifespans and reduced downtime contribute to higher
production efficiency and increased output, ultimately improving the bottom line.
CONCLUSION
Mold wear is an inherent challenge in manufacturing that can lead to significant economic losses and production
disruptions. Tungsten carbide, with its exceptional hardness, wear resistance, and high-temperature stability,
offers a compelling solution to combat mold wear effectively. By investing in tungsten carbide molds,
manufacturers can extend mold lifespans, lower scrap and rework costs, improve product quality, and enhance
overall production efficiency. In doing so, they not only reduce economic losses but also position themselves for
greater success in an increasingly competitive manufacturing landscape.
