\n| Signs requiring corrective action<\/td>\n | Delamination from the base metal, cracking into the base metal or significant porosity<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n The 3 to 12 mm range, with a maximum of 18 mm, is reference data from two-component wear-resistant plates manufactured under controlled factory conditions.<\/p>\n This range should not be used as the default thickness for every on-site hardfacing application.<\/p>\n The actual thickness must still be determined according to the material, component and applicable welding procedure.<\/p>\n 8. Not all cracks in the wear-resistant layer have the same significance<\/span><\/h2>\nIn certain carbide-rich hardfacing deposits, small, regular cracks running across the weld direction may be a characteristic of the hardfacing system.<\/p>\n These cracks are associated with shrinkage stresses as the deposited layer cools.<\/p>\n The important distinction is whether the cracks remain within the deposited layer or extend into the base metal.<\/p>\n \n\n\n| Indication<\/th>\n | Assessment according to the documentation<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Small, regular cracks running across the weld direction and terminating within the deposited layer<\/td>\n | May be a characteristic of the wear-resistant layer<\/td>\n<\/tr>\n | \n| Cracks extending into the base metal<\/td>\n | Require inspection and corrective action<\/td>\n<\/tr>\n | \n| Delamination of the deposited layer in sections<\/td>\n | The underlying layer, deposited thickness and bond condition need to be reassessed<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Acceptance criteria should therefore not simply state that the surface must be free of cracks.<\/p>\n Crack location, morphology and depth must be described.<\/p>\n Check cracking should not be assessed based on terminology alone. Cracks around an indentation on the working surface and a regular crack network within the hardfacing layer do not necessarily have the same technical significance.<\/p>\n 9. The functional profile must be recorded before restoration<\/span><\/h2>\nFor components such as:<\/p>\n \n- Fan blades<\/li>\n
- Separator blades<\/li>\n
- Pump casings<\/li>\n<\/ul>\n
surface geometry directly affects operating performance.<\/p>\n A hardfacing layer may achieve the required hardness, but the component may still fail to perform correctly if its profile has changed during restoration.<\/p>\n Before hardfacing, the required geometry should be recorded using one of the following methods:<\/p>\n \n- Profile measurement<\/li>\n
- Profile tracing<\/li>\n
- Template preparation<\/li>\n<\/ul>\n
If measurements are only taken after hardfacing has been completed, the original reference needed to verify the restored geometry may already have been lost.<\/p>\n This reinforces an important principle from the overview article: achieving the required hardness does not guarantee component performance if the restored profile is incorrect.<\/p>\n 10. Restoration history is part of the technical decision<\/span><\/h2>\nEach hardfacing restoration introduces an additional thermal cycle into the base metal.<\/p>\n After multiple restorations, the condition of the heat-affected region may continue to change.<\/p>\n The number of previous restorations is therefore more than administrative information. It is essential technical data when determining whether a component remains suitable for further hardfacing.<\/p>\n The maintenance records must clearly indicate:<\/p>\n How many times has this component been restored?<\/p>\n The available documentation does not specify a universal maximum number of restorations applicable to all components.<\/p>\n This limit must be determined for each component type and should not be established through estimation.<\/p>\n 11. Items to inspect after restoration<\/span><\/h2>\nAfter hardfacing, at least four groups of items must be inspected.<\/p>\n \n\n\n| Inspection item<\/th>\n | Method<\/th>\n | Signs requiring corrective action<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Hardfaced surface hardness<\/td>\n | Appropriate hardness testing equipment<\/td>\n | Hardness below the specified requirement<\/td>\n<\/tr>\n | \n| Crack condition<\/td>\n | Visual inspection and assessment of crack location<\/td>\n | Cracks extending into the base metal or delamination in sections<\/td>\n<\/tr>\n | \n| Component profile<\/td>\n | Compare against the template or profile recorded before restoration<\/td>\n | Deviation from the required restored geometry<\/td>\n<\/tr>\n | \n| Mating dimensions<\/td>\n | Calipers, micrometers or other appropriate measuring instruments<\/td>\n | Dimensions outside the applicable tolerances<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n During crack inspection, a fine crack network confined to the deposited layer must not be treated as equivalent to cracking that extends into the base metal.<\/p>\n When inspecting the component profile, the results are only meaningful if the reference geometry was recorded before restoration began.<\/p>\n 12. Restoration records must retain sufficient data for future maintenance<\/span><\/h2>\nA restoration record should include at least the following information:<\/p>\n \n\n\n| Record item<\/th>\n | Information to retain<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Component<\/td>\n | Component name and location within the equipment<\/td>\n<\/tr>\n | \n| Restoration history<\/td>\n | Number of previous restorations<\/td>\n<\/tr>\n | \n| Hardfacing materials<\/td>\n | Materials used for the build-up layer and wear-resistant layer, including applicable classification information<\/td>\n<\/tr>\n | \n| Welding process<\/td>\n | Number of passes, actual preheating temperature and interpass temperature<\/td>\n<\/tr>\n | \n| Component profile<\/td>\n | Photographs or measurement data before and after restoration<\/td>\n<\/tr>\n | \n| Personnel<\/td>\n | Welder, inspector and date of work<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Among these records, the number of previous restorations is particularly important.<\/p>\n If this history is lost, the next maintenance team may be unable to determine whether the component is undergoing its first restoration or has already been subjected to several hardfacing cycles.<\/p>\n 13. Responsibilities during component restoration<\/span><\/h2>\nThe decision to restore or replace a component involves more than one department.<\/p>\n \n\n\n| Task<\/th>\n | Responsible department or personnel<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Assess component condition and suitability for further restoration<\/td>\n | Engineering team in coordination with maintenance planning<\/td>\n<\/tr>\n | \n| Provide lead time for a replacement component<\/td>\n | Procurement team<\/td>\n<\/tr>\n | \n| Record the component profile before hardfacing<\/td>\n | Workshop<\/td>\n<\/tr>\n | \n| Select materials for the build-up and wear-resistant layers<\/td>\n | Engineering team, based on the applicable technical documentation<\/td>\n<\/tr>\n | \n| Measure preheating and interpass temperatures<\/td>\n | Welder, with measurements recorded<\/td>\n<\/tr>\n | \n| Maintain records of previous restorations<\/td>\n | Engineering team, in the equipment maintenance records<\/td>\n<\/tr>\n | \n| Inspect the profile and dimensions after restoration<\/td>\n | Inspection team, according to component requirements<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n The lead time for a replacement component is important information, but it is not determined solely by the engineering team.<\/p>\n The restoration-or-replacement decision should therefore combine engineering, maintenance and procurement information rather than relying only on the visible condition of the component surface.<\/p>\n 14. Scope of application and references<\/span><\/h2>\nThis article focuses on the evaluation and control of component restoration by hardfacing, from deciding whether to restore a component through dimensional rebuilding, application of the wear-resistant layer, inspection and recordkeeping.<\/p>\n Several parameters must still be determined according to the specific component and welding procedure, including:<\/p>\n \n- Minimum remaining base-metal thickness required for restoration<\/li>\n
- Number of passes and thickness per pass in certain applications<\/li>\n
- Maximum number of restorations permitted for each component type<\/li>\n<\/ul>\n
These values should not be established through assumptions.<\/p>\n Three points should be considered when applying this article.<\/p>\n First, the maximum number of restorations depends on the component type. This article explains why restoration history must be maintained but does not establish a universal limit.<\/p>\n Second, the functional profile can only be reliably restored and inspected when the required geometry has been recorded beforehand using a template, profile data or another appropriate method.<\/p>\n Third, this article does not replace an approved welding procedure. Preheating, interpass temperature, welding consumables and other related requirements must still be determined according to the applicable procedure.<\/p>\n EN 14700 is referenced for the classification of hardfacing consumables according to their intended applications.<\/p>\n The distinction between dimensional build-up and wear-resistant layers, the effects of accumulated heat, profile documentation and restoration-history management are incorporated into Gia Anh’s technical methodology and practical field experience.<\/p>\n <\/p>\n","protected":false},"featured_media":8723,"parent":9452,"menu_order":8,"template":"","meta":{"_acf_changed":false,"inline_featured_image":false},"danh-muc-kien-thuc":[277],"class_list":["post-9463","kien-thuc","type-kien-thuc","status-publish","has-post-thumbnail","hentry","danh-muc-kien-thuc-machining-fabrication-and-installation"],"acf":[],"_links":{"self":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/kien-thuc\/9463","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/kien-thuc"}],"about":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/types\/kien-thuc"}],"up":[{"embeddable":true,"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/kien-thuc\/9452"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/media\/8723"}],"wp:attachment":[{"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/media?parent=9463"}],"wp:term":[{"taxonomy":"danh-muc-kien-thuc","embeddable":true,"href":"https:\/\/giaanh.vn\/en\/wp-json\/wp\/v2\/danh-muc-kien-thuc?post=9463"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | | | | |