7-Engineering Alloys

carbide forming elements cr mo v ti w austenite

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Unformatted text preview: ation resistance" must be rapidly quenched leading to problems" " 5. "have poor impact resistance at low temperature" ALLOY STEELS Alloying elements added to improve properties." Molybdenum " Chromium " Nickel " Manganese "high temperature strength" "corrosion and oxidation resistance" "corrosion resistance" "high strength" LOW ALLOY STEELS Alloying elements affect phase equilibria." Carbide forming elements: Cr, Mo, V, Ti, W" " Austenite stabilizing elements: Mn, Ni" HARDENABILITY Property of a steel which determines the depth and distribution of hardness induced by quenching from austenite." " " " Good hardenability is indicated by a greater depth of hardening below the surface." HARDENABILITY OF STEEL Depends on:" Composition shift " Austenite grain size "IT or CT diagrams" "Increased grain size increases hardenability." " Structure of austenite "Distribution of alloying elements must be homogeneous with separate phases present." FACTORS AFFECTING DEPTH OF HARDENING " 1. " 2. " 3. " 4. " 5. "Hardenability of steel" "Seventy of quench" "Agitation" "Size and shape of the component" "Surface condition" SEVERITY OF QUENCH Cooling rate of a given component depends upon the" quenching medium." " Air" " Oil " cooling" " Water " rate" " Salt or Brine Water " increases" MEASUREMENT OF HARDENABILITY Jominy Test " Measurement of the effect of composition on the depth of hardening (hardenability)." " All other factors are held constant." JOMINY TEST CONDITIONS Severity of quench " Agitation " Size and shape " Surface condition " Grain size "Use water at 20ºC at a fixed rate of flow." "Fixed." "Fixed. Surface to mass ratio is constant for all comparisons." "Fixed. Heated in a non-oxidizing atmosphere." "Fixed. Time and temperature of heat treatment." STEPS IN JOMINY TEST Heat treatment - austenitize" " Cool in fixture" "Specimen at water end is cooled faster than other end. Variation in cooling rate." " Grind flat on cylinder" " Hardness measurements (Rc) " " Plot hardness vs. distance from quenched end." Jominy Test Results for Different Alloys Aluminum Alloys Aluminum Alloys: Precipitation Aluminum Alloys: Precipitation Aluminum-Copper Phase Diagram Aluminum Alloys: Precipitation Aluminum Alloys: Precipitation Aluminum Alloys: Precipitation Aluminum Alloys: Precipitation Aluminum Alloys: Precipitation Liquid Phase Sintering of Alloys Nickel-based Superalloys: Gamma-Gamma Prime Alloys...
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This document was uploaded on 02/27/2014 for the course NANO 108 at UCSD.

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