Laser Heat Treating Fundamentals and Practice NSF Workshop – Fluid Power Advanced Manufacturing May 24th, 2016

Joel DeKock, PhD Preco, Inc.

www.precoinc.com 6/2/2016

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Outline     

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Introduction Materials & Transformation Hardening Laser Light Sources Delivery of Light to the Workpiece Case Studies

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Introduction Heat treating is a rather vague term that can mean something different to each individual based upon their experiences. This presentation will emphasize transformation hardening of steels and irons, but the laser can be used to heat affect materials in other ways. As a process it is very dependent upon the efficient absorption of the energy from light and the control of this energy.

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Introduction - Laser Materials Processes

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Materials & Transformation Hardening  Phase Equilibrium of Steels  Crystalline Structure Change  Alloy Elements and Their Effects  Hardness as a Function of Carbon  Carbon/Martensite Relationship  Carbon/Retained-Austenite Relationship  The Time-Temperature Constraint  ‘Ideal’ Materials for Laser Treating

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Materials – Phase Equilibrium

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Materials – Phase Equilibrium

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Materials - Crystalline Structure Change

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Materials - Crystalline Structure Change

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Materials – Alloy Elements      

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Fe – Base element (‘Solvent’) Carbon – Solute atom effective in Austenite stabilization, which occupies interstitial sites in the crystalline structure. Manganese & Nickel – Austenite stabilizers. Silicon, Chromium & Niobium – Ferrite stabilizers. Ferrite & Austenite stabilizers expand the respective phase fields and affect hardenability. Some elements are strong carbide formers.

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Materials – Hardness & Carbon Relationship

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Materials – Carbon/Martensite Relationship

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Materials – Carbon/Retained-Austenite Relationship

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Materials – Time & Temperature Constraint

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‘Ideal’ Materials for Laser Hardening Common materials treated include plain-carbon steels (1045), low-alloy steels(4140), grey iron, ductile iron and martensitic stainless steels (420) Materials respond favorably when mircrostructure has fine and uniform distribution of carbon. Normalized and quenched & tempered are materials ideal High-alloy and tool steels typically are not well suited to laser hardening Laser hardened products are often used as treated so chemistry is an important consideration for each application Sufficient mass or hardenability needed for self-quenching

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Laser Light Sources

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Nd:YAG Lasers CO2 Lasers Direct Diode Lasers Fiber & Disk Lasers

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Laser Light Sources - Laser Wave Lengths  10.6 microns - CO2  1 micron - Direct Diode, Fiber Deliver Direct Diode, Disk and Fiber, and Nd:YAG

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Laser Light Sources - Absorption

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Laser Light Sources – Beam Quality

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Delivery of Light to the Workpiece

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CO2 Lasers – Mirrors in a rigid sealed system Diode Lasers - Direct, and flexible glass fiber

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Fiber & Disk – Flexible glass fiber

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Delivery of Light to the Workpiece • Needs to be considered in application evaluation phase • Complex component for laser processing, difficult and expensive to source and get custom optics. Usually end up using generic products • Poor beam delivery + good laser = bad results and vice a versa • Optics for polarization (sometimes overlooked with new products)

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Delivery of Light to the Workpiece - Integration

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Delivery of Light to the Workpiece – Square Fiber

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Delivery of Light to the Workpiece – Axicon

Ring Analysis ~29.7mm ~15.6mm

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Delivery of Light to the Workpiece - Scanner

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Delivery of Light to the Workpiece - Scanner

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Delivery of Light to the Workpiece – Multi-Spot

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Case Studies – Large Surface Challenge Two or more passes needed

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Circular part

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Case Studies – Multi-Pass Shaft

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Case Studies – Multi-Pass Engine Liner

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Case Studies – Basic Single Spot with Integration

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Thus no extraordinary processing procedures are necessary in order to heat treat steels to an acceptable case depth using a laser with a wavelength of 1.07um. A single beam through optic integrator was used to modify the beam into a usable tool to heat treat the surface. As shown, a laser with using an integrated beam can produce a wide and deep heat treated zone. The width of the HAZ at a minimum depth of 0.020” is 0.745” and can be accomplished with one pass without pre treating the surface of the component. 31

Case Studies – Drive Side of Gear Tooth  One side of the gear required case hardening.  The gear material: AISI 4140  The base material normalized with a hardness was in the low 30’sHRC.  The case hardness ranged from 56-58HRC  The hardness path could not extend to the root, and minimum case depths were specified.  A fiber laser with a through optic focusing optic was used to apply a case hardened zone as shown in the photo.

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Case Studies – Multi-Spot on Flute Profile Dual-Beam Heat Treating  Increased Productive  Reduced Heat Effects

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Case Studies – Camshaft Lobes with Power Control

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Case Study- Camshaft Lobe Case Hardened Zone

•A cross-section of a cam lobe is shown (left). The white arrow shows the case hardened location. •The corresponding Process Diagram created during the case hardening of this part is shown at right

Process Diagram

• The ATemp (Actual temp); STemp (Set temp) and ConOut (Control power out) is displayed in the Process Diagram. • The power is steady until the 7 ½ second mark. • •

The lobe tip approaches the laser beam. Control system senses that less power is required to maintain the set temperature.

• At 10 seconds, the lobe tip is rotating through the beam, the system senses that even less power (20%) is required to maintain the ideal hardening temperature. • As the component is rotated beyond the tip of the cam lobe, the Thermal Feedback System increases laser power to maintain the ideal hardening temperature.

Preco Thermal Feedback Sensor

• Added a closed loop, thermal feedback control sensing system to our tool box. • Used in many case hardening processes. • Measures surface temperature of the component being case hardened. • Increases consistency of case hardened zone. • Prevents overheating/ under heating due to surface absorption characteristic changes. • Controls the laser power to maintain the set temperature . • The surface temperature of the component is continuously monitored during the heat treating (surface hardening) process. • A thermal history of each heat treated part is created as a Process Diagram.

Preco, Inc.

Preco Headquarters 9705 Commerce Parkway Lenexa, Kansas 66219 Toll Free: 800.966.4686 Phone: 913.541.0066 Fax: 913.541.9088

Preco Somerset 500 Laser Drive Somerset, Wisconsin 54025 Toll Free: 800.775.2737 Phone: 715.247.3285 Fax: 715.247.5650

Other Locations:

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Preco United Kingdom

Preco LMI AB Sweden

Preco Miwa China

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