本文選題：B2模具鋼　切入點：激光熔覆層　出處：《吉林大學》2015年碩士論文　論文類型：學位論文

【摘要】：沖壓模具在使用過程因承受交變載荷作用而發(fā)生腐蝕、磨損、疲勞和斷裂等各種形式的失效。本文針對沖壓模具使用過程中的失效問題，特別是模具刃角部位的性能與模具整體壽命不匹配的問題，采用激光熔覆的方法，對沖壓模具失效表面進行修復。試驗在B2模具鋼基體制備了Ni60A熔覆層和Ni60A+WC熔覆層，研究了熔覆層的組織與性能，分析了工藝參數(shù)和熔覆合金成分對熔覆層組織與性能的影響。 熔覆試件由熔覆層、熱影響區(qū)和基體三部分組成。Ni60A熔覆層組織由底部胞狀晶和上部樹枝晶組成，胞狀晶為γ-(Fe,Ni)相，樹枝晶為Cr2Ni3，，樹枝晶間分布著M23C6和CrB等強化相。熔覆層顯微硬度在570~580HV之間，基體顯微硬度在400~420HV之間。熔覆層表面的磨痕犁溝窄且淺，凹坑數(shù)量較少，耐磨性能優(yōu)于基體。加載載荷F=15KN，循環(huán)次數(shù)N=2×104時，熔覆層氣孔處產(chǎn)生裂紋源；N=3×104時，熔覆層在硬質(zhì)相處產(chǎn)生裂紋源；N=4×104時，熔覆層與基體熔合線處產(chǎn)生裂紋源；N=5×104時，熔覆層在γ相內(nèi)部產(chǎn)生疲勞裂紋。 試驗研究了工藝參數(shù)對Ni60A熔覆層組織和性能的影響。結果表明，隨脈沖電流增大，熔覆層底部胞狀晶變得均勻致密，脈沖電流大于80A時，基體與熔覆層之間形成亮白色的條帶狀區(qū)域；隨脈寬值增加，熔覆層上部樹枝晶形態(tài)變得粗大；頻率的變化對熔覆層的組織沒有顯著影響。熔覆層顯微硬度隨脈沖電流增大而降低，由熔覆層到基體的變化趨勢隨脈寬增加而變得顯著，隨頻率的改變變化不明顯。熔覆層稀釋率隨脈沖電流、頻率和脈寬的增加而增大。 試驗研究了WC含量對Ni60A+WC熔覆層組織和性能的影響。ω(WC)=10wt%時，WC大部分熔解在熔覆層中，促進了Cr23C6、Cr4Ni15W和Cr3Ni2Si等強化相的形成；ω(WC)=20wt%時，熔覆層上部樹枝晶消失，形成塊狀晶，組織更為細化；ω(WC)=30wt%時，熔覆層的組織為富W塊狀共晶，其間含有未熔解的WC和部分W、Cr的碳化物和硼化物。Ni60A+WC熔覆層顯微硬度隨WC含量增加而增大，最高為1520HV，明顯高于Ni60A熔覆層。Ni60A+WC熔覆層的耐磨性因WC顆粒的加入得以改善，磨痕表面犁溝較Ni60A熔覆層窄且淺，凹坑數(shù)量也較少。WC含量為35%時，Ni60A+WC熔覆層磨痕表面有大塊硬質(zhì)相顆粒脫落。承受F=15KN，N=5×104的交變載荷時，Ni60A+WC熔覆層以剝離裂紋的形式從基體表面脫落。ω(WC)≤15wt%時，熔覆層剝落的厚度較小，疲勞性能較好；ω(WC)≥20wt%時，熔覆層剝落的厚度隨WC含量的增加而增加；ω(WC)≥30wt%時，熔覆層全部從基體脫落。
[Abstract]:In the process of using stamping die, corrosion, wear, fatigue and fracture occur due to the action of alternating load. Especially, the failure surface of stamping die was repaired by laser cladding, the Ni60A cladding layer and Ni60A WC cladding layer were prepared on B2 die steel substrate. The microstructure and properties of the cladding were studied, and the effects of process parameters and alloy composition on the microstructure and properties of the cladding were analyzed. The cladding specimen consists of a cladding layer, a heat-affected zone and a matrix. The microstructure of the cladding layer is composed of cellular crystal at the bottom and dendrite in the upper part, and the cellular crystal is 緯 -fen Fe Ni) phase. The microhardness of the cladding layer is between 570,580HV and 400-420HV. The surface of the cladding layer is narrow and shallow, and the number of pits is relatively small, and the microhardness of the cladding layer is Cr _ 2Ni _ 3, and M23C6 and CrB are distributed among the dendrites, and the microhardness of the cladding layer is between 570,580HV and 400-420HV. The wear resistance of the cladding is better than that of the matrix. When the loading load is F _ (15) KN, the cycle number is N ~ (2 脳 10 ~ 4), the crack source is 3 脳 10 ~ 4 at the porosity of the cladding layer, the crack source N _ (4 脳 10 ~ 4) is produced in the cladding layer when the crack source is N4 脳 10 ~ 4, the crack source is N _ (5) 脳 10 ~ 4 at the fusion line between the cladding layer and the matrix. Fatigue cracks occur in the 緯 phase of the cladding layer. The effect of process parameters on the microstructure and properties of Ni60A cladding coating was studied. The results show that the cellular crystal at the bottom of the cladding layer becomes uniform and compact with the increase of pulse current, and the pulse current is greater than 80A. A bright white stripe region was formed between the substrate and the cladding layer, and the dendritic morphology of the upper cladding became coarse with the increase of the pulse width. The change of frequency has no significant effect on the microstructure of the cladding layer. The microhardness of the cladding layer decreases with the increase of pulse current, and the change trend from the cladding layer to the substrate becomes obvious with the increase of pulse width. The dilution rate of cladding layer increases with the increase of pulse current, frequency and pulse width. The effect of WC content on the microstructure and properties of Ni60A WC cladding coating was studied. When the content of WC was 10 wt%, most of WC was melted in the cladding layer, which promoted the formation of strengthening phases such as Cr23C6C6Cr4Ni15W and Cr3Ni2Si. The microhardness of the cladding layer increases with the increase of WC content, the microstructure of the cladding layer is W-rich bulk eutectic, and the microhardness of WC and boride. Ni60A WC cladding coating increases with the increase of WC content, while the microstructure of the coating is more fine, and the microhardness of the cladding coating increases with the increase of WC content, and the microhardness of the cladding coating increases with the increase of WC content. The wear resistance of WC cladding layer is obviously higher than that of Ni60A cladding coating. The wear resistance of WC cladding coating is improved because of the addition of WC particles, and the ploughing groove on the surface of wear mark is narrower and shallower than that of Ni60A cladding coating. The number of pits is also less .WC content is 35% and Ni60A WC cladding layer has large hard phase particles falling off on the surface of wear mark. The Ni60A WC cladding layer shedding from the substrate surface in the form of peeling crack when the FN 15KN NU 5 脳 10 4 AC cladding layer is subjected to the alternating load. 蠅 WC鈮

本文編號：1632204