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標題: | 利用惰性氣體鎢極銲覆之被覆層微觀結構及磨耗特性研究 A Study on Microstructures and Wear Behaviors of Cladding Layer Generated by Gas Tungsten Arc W elding |
作者: | Yu-Chi Lin 林育奇 |
指導教授: | 陳永傳 |
關鍵字: | 氣體遮護鎢弧銲被覆,被覆層,顯微結構,碳化矽,碳化鎢,硼化鎢,氮化鈦,工具鋼,鈦合金, Gas tungsten arc welding,Clad layer,Microstructure,Silicon carbide,Tungsten carbide,Tungsten boride,Titanium nitride,Tool steel,Titanium alloy, |
出版年 : | 2014 |
學位: | 博士 |
摘要: | 本論文將JIS SKD11 工具鋼、JIS SKD61 模具鋼及Ti-6Al-4V 鈦合金基材表
面施以氣體遮護鎢弧銲被覆(Gas Tungsten Arc Welding, GTAW)表面強化處理,研究強化材料種類對於被覆層之顯微組織、機械性質及耐磨耗能力的影響,並將相關結果整理成可供人們參考使用的資料庫,資料庫中包含被覆參數、硬度及被覆層的強化相等相關資料。本論文主要分為三大部分進行探討: (一) 分別被覆四種不同陶瓷粉末做為JIS SKD11 工具鋼基材之強化 JIS SKD11 工具鋼表面分別被覆不同的四種陶瓷粉末(碳化矽(SiC)、碳化鎢 (WC)、硼化鎢(WB)與氮化鈦(TiN))後進行被覆層厚度之量測,其中以WB 粉末 之被覆層最厚(約6 mm),而TiN 粉末之被覆層最薄(約0.3 mm)。經由被覆層組 成相之分析結果得知SiC 粉末之被覆層主要由 [Cr,Fe]7C3+Fe0.905Si0.095 共晶組織與Fe0.905Si0.095 等相為主,WC 粉末之被覆層中主要以FexWxC(x=2,3) 與M3C(M=Fe,Cr,W) 等相為主, WB 粉末之被覆層則以α -Fe 與Fe23B6+M23C6(M=Fe,Cr,W)共晶組織等相為主,最後TiN 粉末之被覆層以TiN 與α-Fe+Cr1.97Ti1.07 等相為主。經維克氏硬度量測後得知,TiN 粉末之被覆層有最高的硬度(約2200-2300 HV),SiC 粉末之被覆層硬度最低(約750-820 HV)。雖然SKD11 工具鋼被覆層有高硬度,但是在被覆過後的熱影響區卻因為基材本身高Cr 及C 的含量,導致顯微組織中殘留較多的沃斯田鐵,使熱影響區明顯軟化。利用奈米壓痕器針對被覆層中各組成相進行硬度及彈性係數之量測,其結果顯示WB粉末之被覆層中的Fe23B6+M23C6(M=Fe,Cr,W)共晶組織有最高的硬度(約21.9GPa),而TiN 粉末之被覆層中的TiN 相有最高的彈性係數(374 GPa)。經由耐磨耗實驗評估,結果顯示所有的被覆層耐磨耗能力皆比原材好,也優於熱處理過後的SKD11,其中以WC 粉末之被覆層有最佳的耐磨耗能力,其歸因於WC 粉末之被覆層中幾何形狀複雜的FexWxC(x=2,3)與M3C(M=Fe,Cr,W)所產生的機械固鎖效應,使強化相在磨耗過程中不易脫落或移除。 (二) 分別被覆四種不同陶瓷粉末做為JIS SKD61 模具鋼基材之強化 為了瞭解基材的種類對於被覆層之組成相及機械性質等之影響,在JIS SKD61 模具鋼表面分別被覆上述四種陶瓷粉末後進行被覆層厚度之量測,其同 樣地以WB 粉末為強化來源之被覆層最厚(約6 mm),而TiN 粉末之被覆最薄(約 0.3 mm),然而被覆SiC 粉末與WC 粉末之被覆層厚度相較於SKD11 工具鋼約厚 0.4 mm。經由被覆層組成相之分析得知SiC 粉末之被覆層主要由 Fe8Si2C、 α-Fe+Fe8Si2C 共晶組織、Fe3C+Fe8Si2C 共晶組織與graphite 等相為主,WC 粉末之被覆層中主要以FexWxC(x=2,3)與M7C3(M=Fe, W, Cr)等相為主,WB 粉末之被覆層則以α-Fe 與FeWB 等相為主,最後TiN 粉末之被覆層以TiN、α-Fe 與Fe9.64Ti0.36 等相為主。經維克氏硬度量測後得知,TiN 粉末之被覆層有最高的硬度(約2100-2200 HV),WB 粉末之被覆層硬度最低(約1050-950 HV)。SKD61 之熱影響區與SKD11 之熱影響區不同,SKD61 之熱影響區沒有軟化區產生,經由SEM 觀察發現,其組織為麻田散鐵。利用奈米壓痕器針對被覆層中各組成相進行硬度及彈性係數之量測,其結果顯示WC 粉末之被覆層中的FexWxC(x=2,3)有最高的硬度(約22.1 GPa),而TiN 粉末之被覆層中的TiN 相有最高的彈性係數(375GPa)。經由耐磨耗實驗評估,結果顯示所有的被覆層耐磨耗能力皆比原材好,也優於熱處理過後的SKD61,其中以TiN 粉末之被覆層在低滑度速度條件下有最佳的耐磨耗能力,其歸因於高硬度的TiN 強化相,而在高滑度速度條件下WC粉末之被覆層有最佳的耐磨耗能力,這是因為在高滑度速度時磨耗表面易生成氧化膜,氧化膜產生的裂縫及黏著磨耗使TiN 強化相易於磨耗表面脫落,因此使磨耗量略高於WC 粉末之被覆層。 (三) 藉由氮氣保護氣體與Ti-6Al-4V 鈦合金的高溫化學反應來強化基材 有別於傳統的GTAW 被覆處理,本研究將常用來當作保護氣體的氬氣改變 為氮氣,藉由氮氣與鈦合金的高溫化學反應生成氮化鈦來強化鈦合金基材。經由 不同的被覆參數結果得知以7.2 kJ/cm 的入熱量進行被覆能有最佳的氮化鈦被覆 層,其中包含了最佳的表面粗糙度及最厚的氮化鈦被覆層。經由被覆層組成相之 分析結果指出氮化鈦被覆層中主要以TiN 相及α’-Ti 為主,而熱影響區之顯微組 織為麻田散體。由維克氏硬度量測得知,被覆層硬度為1800 HV,其熱影響區硬 度約為450 HV。利用奈米壓痕器針對被覆層中各組成相進行硬度及彈性係數之 量測,其結果顯示氮化鈦被覆層中的TiN 相硬度為18.16 GPa,彈性係數為227 GPa。經由磨耗試驗評估,氮化鈦被覆層的耐磨耗能力遠優於基材。 In this study, JIS SKD11 tool steel, JIS SKD61 die steel and Ti-6Al-4V titanium alloy were treated by gas tungsten arc welding (GTAW) surface modification. The influences of the mechanical properties and wear resistance of the clad layers were investigated and the following three topics discussed: 1. Cladding the four different ceramic powders on JIS SKD11 tool steel Four different ceramic powders (silicon carbide (SiC), tungsten carbide (WC), tungsten boride (WB) and titanium nitride (TiN)) are clad on the JIS SKD11 tool steel. The X-ray diffraction analyses indicates the existence of [Cr,Fe]7C3+Fe0.905Si0.095 and Fe0.905Si0.095 in the SiC clad layer, FexWxC(x=2,3) and M3C(M=Fe,Cr,W) in the WC clad layer, α-Fe and Fe23B6+M23C6(M=Fe,Cr,W) in the WB clad layer and TiN and α-Fe+Cr1.97Ti1.07 in the TiN clad layer. In addition, the experimental results show the WB clad layer to be the thickest, at about 6 mm, while the TiN clad layer has the highest hardness, about 2200-2300 HV. The nanoindentation technique is used to measure the hardness and elastic modulus of the reinforcements and matrix. According to the experimental results, the Fe23B6+M23C6(M=Fe,Cr,W) phase in the WB clad layer has the highest hardness, of about 21.9 GPa, and the TiN phase in the TiN clad layer has the highest elastic modulus, of about 374 GPa. The wear resistances of the clad layers surpass those of the untreated specimens, even after heat-treatment. The WC clad layer has the best wear resistance, indicating that the wear resistance abilities of the clad layer are obviously affected by the mechanical locking effect of the complex reinforcements. 2. Cladding the four different ceramic powders on JIS SKD61 die steel. In order to understand the influences of the different substrates, four different ceramic powders (SiC, WC, WB and TiN) are clad on the JIS SKD61 tool steel. The X-ray diffraction analyses indicate the existence of Fe8Si2C, α-Fe+Fe8Si2C, Fe3C+Fe8Si2C and graphite in the SiC clad layer, FexWxC(x=2,3) and M7C3(M=Fe, W, Cr) in the WC clad layer, α-Fe and FeWB in the WB clad layer and TiN and Fe9.64Ti0.36 in the TiN clad layer. According to the experimental results, the TiN clad layer has the best wear resistance, because of the TiN phase in the clad layer. However, in the high sliding speed condition, the wear loss of the TiN clad layer is slightly higher than that of the WC clad layer, because the oxides films dominate the wear behavior of the TiN clad layer at the high sliding speed condition in the wear test. 3. Using nitrogen shielding gas to enhance Ti-6Al-4V titanium alloy. In this study, the nitrogen source is changed from a shielding gas of nitrogen. The effects of the processing parameters on the microstructural evolution, mechanical properties and wear behavior in the Ti-6Al-4V surface are presented. Nitrogen gas as the nitrogen source consists primarily of the TiN phase. The average size of the TiN dendrites is affected by the heat input. When 7.2 kJ/cm heat input is used, a complex dendritic microstructure is achieved, and this is attributed to the higher solubility. It is observed that under all the processing parameters used in this investigation, the clad layer thickness increases with increases in the heat input. Moreover, nanoindentation indicates that the TiN phase has an 18.16 GPa hardness and a 227 GPa elastic modulus. During the sliding wear test, the hard TiN phase in the TiN clad layer provides a strengthening effect. Therefore, the wear performance of the TiN clad layer is substantially better than that of the other specimens under the same test conditions. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/56959 |
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