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Shot Peened Surface Analysis

SHOT PEENED SURFACE ANALYSIS

USING 3D NON-CONTACT PROFILOMETER

Prepared by

CRAIG LEISING

INTRODUCTION

Shot peening is a process in which a substrate is bombarded with spherical metal, glass, or ceramic beads—commonly referred to as “shot”—at a force intended to induce plasticity on the surface. Analyzing the characteristics before and after peening provides crucial insights for enhancing process comprehension and control. The surface roughness and coverage area of dimples left by the shot are especially noteworthy aspects of interest.

Importance of 3D Non-Contact Profilometer for Shot-Peened Surface Analysis

Unlike traditional contact profilometers, which have traditionally been used for shot-peened surface analysis, 3D non-contact measurement provides a complete 3D image to offer a more comprehensive understanding of coverage area and surface topography. Without 3D capabilities, an inspection will solely rely on 2D information, which is insufficient for characterizing a surface. Understanding the topography, coverage area, and roughness in 3D is the best approach for controlling or improving the peening process. NANOVEA’s 3D Non-Contact Profilometers utilize Chromatic Light technology with a unique capability to measure steep angles found on machined and peened surfaces. Additionally, when other techniques fail to provide reliable data due to probe contact, surface variation, angle, or reflectivity, NANOVEA Profilometers succeed.

MEASUREMENT OBJECTIVE

In this application, the NANOVEA ST400 Non-Contact Profilometer is used to measure raw material and two differently peened surfaces for a comparative review. There is an endless list of surface parameters that can be automatically calculated after the 3D surface scan. Here, we will review the 3D surface and select areas of interest for further analysis, including quantifying and investigating the roughness, dimples, and surface area.

NANOVEA

ST400

THE SAMPLE

RESULTS

STEEL SURFACE

ISO 25178 3D ROUGNESS PARAMETERS

SA 0.399 μm Average Roughness
Sq 0.516 μm RMS Roughness
Sz 5.686 μm Maximum Peak-to-Valley
Sp 2.976 μm Maximum Peak Height
Sv 2.711 μm Maximum Pit Depth
Sku 3.9344 Kurtosis
Ssk -0.0113 Skewness
Sal 0.0028 mm Auto-Correlation Length
Str 0.0613 Texture Aspect Ratio
Sdar 26.539 mm² Surface Area
Svk 0.589 μm Reduced Valley Depth
 

RESULTS

PEENED SURFACE 1

SURFACE COVERAGE
98.105%

ISO 25178 3D ROUGNESS PARAMETERS

Sa 4.102 μm Average Roughness
Sq 5.153 μm RMS Roughness
Sz 44.975 μm Maximum Peak-to-Valley
Sp 24.332 μm Maximum Peak Height
Sv 20.644 μm Maximum Pit Depth
Sku 3.0187 Kurtosis
Ssk 0.0625 Skewness
Sal 0.0976 mm Auto-Correlation Length
Str 0.9278 Texture Aspect Ratio
Sdar 29.451 mm² Surface Area
Svk 5.008 μm Reduced Valley Depth

RESULTS

PEENED SURFACE 2

SURFACE COVERAGE 97.366%

ISO 25178 3D ROUGNESS PARAMETERS

Sa 4.330 μm Average Roughness
Sq 5.455 μm RMS Roughness
Sz 54.013 μm Maximum Peak-to-Valley
Sp 25.908 μm Maximum Peak Height
Sv 28.105 μm Maximum Pit Depth
Sku 3.0642 Kurtosis
Ssk 0.1108 Skewness
Sal 0.1034 mm Auto-Correlation Length
Str 0.9733 Texture Aspect Ratio
Sdar 29.623 mm² Surface Area
Svk 5.167 μm Reduced Valley Depth

CONCLUSION

In this shot-peened surface analysis application, we have demonstrated how the NANOVEA ST400 3D Non-Contact Profiler precisely characterizes both the topography and nanometer details of a peened surface. It is evident that both Surface 1 and Surface 2 have a significant impact on all the parameters reported here when compared to the raw material. A simple visual examination of the images reveals the differences between the surfaces. This is further confirmed by observing the coverage area and the listed parameters. In comparison to Surface 2, Surface 1 exhibits a lower average roughness (Sa), shallower dents (Sv), and reduced surface area (Sdar), but a slightly higher coverage area.

From these 3D surface measurements, areas of interest can be readily identified and subjected to a comprehensive array of measurements, including Roughness, Finish, Texture, Shape, Topography, Flatness, Warpage, Planarity, Volume, Step-Height, and others. A 2D cross-section can quickly be chosen for detailed analysis. This information allows for a comprehensive investigation of peened surfaces, utilizing a complete range of surface measurement resources. Specific areas of interest could be further examined with an integrated AFM module. NANOVEA 3D Profilometers offer speeds of up to 200 mm/s. They can be customized in terms of size, speeds, scanning capabilities, and can even comply with Class 1 Clean Room standards. Options like Indexing Conveyor and integration for Inline or Online usage are also available.

A special thanks to Mr. Hayden at IMF for supplying the sample shown in this note. Industrial Metal Finishing Inc. | indmetfin.com

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