{"id":1256,"date":"2025-11-19T16:45:09","date_gmt":"2025-11-19T08:45:09","guid":{"rendered":"https:\/\/reliablecncmachining.com\/?p=1256"},"modified":"2025-11-19T16:45:09","modified_gmt":"2025-11-19T08:45:09","slug":"key-points-of-metallographic-inspection-in-cnc-machining-services","status":"publish","type":"post","link":"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/","title":{"rendered":"Key points of metallographic inspection in CNC machining services"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_73 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Basculer la table des mati\u00e8res\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Key_Points_of_Metallographic_Testing_for_CNC_Machining_Services\" title=\"Key Points of Metallographic Testing for CNC Machining Services\">Key Points of Metallographic Testing for CNC Machining Services<\/a><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Sample_Preparation_for_Metallographic_Testing\" title=\"Sample Preparation for Metallographic Testing\">Sample Preparation for Metallographic Testing<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Selection_of_Sampling_Locations\" title=\"Selection of Sampling Locations\">Selection of Sampling Locations<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Sampling_Directions\" title=\"Sampling Directions\">Sampling Directions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Sampling_Methods\" title=\"Sampling Methods\">Sampling Methods<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Microstructure_Observation_Techniques\" title=\"Microstructure Observation Techniques\">Microstructure Observation Techniques<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Optical_Microscope_Observation\" title=\"Optical Microscope Observation\">Optical Microscope Observation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Scanning_Electron_Microscope_Observation\" title=\"Scanning Electron Microscope Observation\">Scanning Electron Microscope Observation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Electrolytic_Etching_and_Chemical_Etching\" title=\"Electrolytic Etching and Chemical Etching\">Electrolytic Etching and Chemical Etching<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Quality_Evaluation_Based_on_Metallographic_Testing_Results\" title=\"Quality Evaluation Based on Metallographic Testing Results\">Quality Evaluation Based on Metallographic Testing Results<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Grain_Size_Evaluation\" title=\"Grain Size Evaluation\">Grain Size Evaluation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Phase_Composition_Analysis\" title=\"Phase Composition Analysis\">Phase Composition Analysis<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/reliablecncmachining.com\/fr\/key-points-of-metallographic-inspection-in-cnc-machining-services\/#Non-Metallic_Inclusion_Detection\" title=\"Non-Metallic Inclusion Detection\">Non-Metallic Inclusion Detection<\/a><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h1><span class=\"ez-toc-section\" id=\"Key_Points_of_Metallographic_Testing_for_CNC_Machining_Services\"><\/span>Key Points of Metallographic Testing for CNC Machining Services<span class=\"ez-toc-section-end\"><\/span><\/h1>\n<h2><span class=\"ez-toc-section\" id=\"Sample_Preparation_for_Metallographic_Testing\"><\/span>Sample Preparation for Metallographic Testing<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Selection_of_Sampling_Locations\"><\/span>Selection of Sampling Locations<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>The accuracy of metallographic testing results largely depends on the rationality of sampling locations. For CNC-machined components, sampling should be carried out in areas that can truly reflect the material\u2019s performance or failure characteristics. For example, in parts with cracks, the crack source area and the crack propagation area should be included. In welded components, samples should be taken from the base material, heat-affected zone, fusion line, and weld seam area to comprehensively evaluate the welding quality. Avoid areas affected by cutting, processing, or environmental factors, such as overheated zones, oxide layers, or deformed layers.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Sampling_Directions\"><\/span>Sampling Directions<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>The sampling direction should be selected according to the testing purpose. For rolled or forged parts, a longitudinal section can be used to observe the deformation direction of grains or fibrous tissues. A transverse section is suitable for analyzing grain size, the distribution of non-metallic inclusions, or surface treatment layers like carburized layers and coating thickness. For anisotropic materials such as composite materials or 3D-printed parts, a normal section can be used to study their anisotropic properties.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Sampling_Methods\"><\/span>Sampling Methods<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Different materials require appropriate cutting methods to minimize damage. For hard materials like quenched steel, wire cutting or slow-speed cutting is preferred to reduce heat accumulation and prevent tissue changes due to high temperatures. For soft materials such as copper and aluminum, excessive extrusion during cutting should be avoided to prevent deformation. During the cutting process, mechanical stress should be controlled to prevent sample deformation or cracking. For materials prone to oxidation, such as magnesium alloys, rapid sample preparation or sealed storage is necessary.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Microstructure_Observation_Techniques\"><\/span>Microstructure Observation Techniques<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Optical_Microscope_Observation\"><\/span>Optical Microscope Observation<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Optical microscopes are commonly used in metallographic testing. When observing samples, the appropriate magnification should be selected based on the sample\u2019s tissue characteristics and testing requirements. For example, to observe the overall distribution of grains, a lower magnification (e.g., 100x) can be used. To analyze the fine structure of phases, a higher magnification (e.g., 500x or 1000x) is more suitable. The light settings of the microscope should be adjusted to make the sample tissue present the best contrast, allowing for clear observation of grain morphology, phase distribution, and non-metallic inclusions.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Scanning_Electron_Microscope_Observation\"><\/span>Scanning Electron Microscope Observation<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Scanning electron microscopes (SEMs) offer higher resolution and can observe the surface morphology and microstructure of samples in greater detail. SEMs can be used to analyze the fracture morphology of failed components, helping to determine the failure mode, such as ductile fracture, brittle fracture, or fatigue fracture. They can also observe the fine structure of phases and the distribution of non-metallic inclusions at a higher magnification, providing more detailed information for material performance evaluation.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Electrolytic_Etching_and_Chemical_Etching\"><\/span>Electrolytic Etching and Chemical Etching<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>To observe the microstructure of samples under a microscope, etching is usually required. Chemical etching uses chemical reagents to selectively corrode the sample surface, highlighting grain boundaries and phase boundaries. The choice of etchant depends on the material composition. For example, a 4% nitric acid alcohol solution is commonly used for carbon steel, while Keller\u2019s reagent (a mixture of HF, HCl, and HNO3) is suitable for aluminum alloys. Electrolytic etching is used for materials with high chemical stability, such as precious metal alloys. It applies a direct current to the sample, and the different phases corrode at different rates due to their different electrode potentials, thus revealing the microstructure.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Quality_Evaluation_Based_on_Metallographic_Testing_Results\"><\/span>Quality Evaluation Based on Metallographic Testing Results<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Grain_Size_Evaluation\"><\/span>Grain Size Evaluation<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Grain size is an important indicator of material properties. Generally, smaller grain size leads to higher strength, hardness, and better toughness and fatigue resistance. The grain size can be evaluated using image processing technology to automatically measure the grain size distribution. According to relevant standards, the average grain size or grain size grade can be determined, and the material\u2019s mechanical properties can be predicted based on the relationship between grain size and properties.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Phase_Composition_Analysis\"><\/span>Phase Composition Analysis<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>The phase composition of an alloy has a significant impact on its performance. By analyzing the phase composition in the metallographic structure, the material\u2019s chemical composition and phase transformation process can be evaluated. For example, in steel, the proportion of ferrite, pearlite, bainite, and martensite affects its strength, hardness, and toughness. In non-ferrous alloys, the type and distribution of phases also determine their performance characteristics. Through phase composition analysis, the heat treatment process can be optimized to obtain the desired phase structure and improve material performance.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Non-Metallic_Inclusion_Detection\"><\/span>Non-Metallic Inclusion Detection<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Non-metallic inclusions in metals come from various sources during the melting and casting process, such as oxides, nitrides, and refractory residues. These inclusions can act as stress concentration points, reducing the material\u2019s mechanical properties, especially fatigue strength and corrosion resistance. According to relevant standards, non-metallic inclusions can be classified and detected, such as sulfides (A-type), alumina (B-type), silicates (C-type), and nitrides (D-type). By analyzing the type, quantity, size, and distribution of non-metallic inclusions, the material\u2019s quality can be evaluated, and measures can be taken to reduce their harmful effects during the smelting and processing process.<\/p>","protected":false},"excerpt":{"rendered":"<p>Key Points of Metallographic Testing for CNC Machining Services Sample Preparation for Metallographic Testing Selection of Sampling Locations The accuracy of metallographic testing results largely depends on the rationality of sampling locations. For CNC-machined components, sampling should be carried out in areas that can truly reflect the material\u2019s performance or failure characteristics. For example, in [\u2026]<\/p>","protected":false},"author":1,"featured_media":704,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[86],"class_list":["post-1256","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","tag-cnc-machining"],"acf":[],"_links":{"self":[{"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/posts\/1256","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/comments?post=1256"}],"version-history":[{"count":0,"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/posts\/1256\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/media\/704"}],"wp:attachment":[{"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/media?parent=1256"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/categories?post=1256"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/reliablecncmachining.com\/fr\/wp-json\/wp\/v2\/tags?post=1256"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}