200829704 九、發明說明： 【發明所屬之技術領域】 本發明係關於 本發明係關於一種鐵基粉末。特定言之 種適用於製造耐磨產品之粉末。 【先前技術】 具有高耐磨性之產品已得到廣泛使用，且不斷需要具有 與現有產品相同或比其更佳之效能的價格較低廉之產品。200829704 IX. INSTRUCTIONS OF THE INVENTION: TECHNICAL FIELD OF THE INVENTION The present invention relates to an iron-based powder. In particular, it is suitable for the manufacture of powders for wear resistant products. [Prior Art] Products having high abrasion resistance have been widely used, and there is a constant need for a less expensive product having the same or better performance as the existing products.
ϋ 製造具有高耐磨性之產品可基於（例如）粉末，諸如鐵或 鐵基粉末，包括碳化物形式之碳。 碳化物通常極硬且具有高㈣，此可在許多應用中提供 高耐磨性之特徵。由於該耐磨性，碳化物常合乎作為需要 高财磨性之鋼中之組件的需要，例如高速鋼（hss)，=如 用於鑽床、車床、閥座及其類似物之鋼。 具有高耐磨性之習知鐵基粉末之實例揭示於（例如）關於 包括工具鋼粉末與精細分散之碳化物之粉末混合物的美國 專利苐6 679 932 $虎及關於不鐘鋼粉末之美國專利第$ 856 625號中。 W、V、Mo、Ti及Nb為能強力形成碳化物之元素，此使 得該等元素尤其受到製造耐磨產品之關注。Cr為另一種能 形成碳化物之元素。然而，大多數該等習知能形成碳化物 之金屬皆係昂貴的且導致不便利之高價產品。因此，粉末 冶金工業中需要一種能向諸如用於閥座或其類似物之壓製 及燒結產品提供足夠耐磨性且價格較低廉之鐵基粉末或高 速鋼。 125100.doc 200829704 絡與用於具有高耐磨性之習知粉末及硬質相之其他該等 金屬相比，乃為更便宜及可更易獲得之能形成碳化物之金 屬’因此宜將鉻作為主要之形成碳化物之金屬。以該方 式’可更廉價地製造該粉末且因此製造壓實產品。 一般高速鋼之碳化物通常相當小，但根據本發明，現已 出乎意料地展示用於（例如）閥座應用之具有同等有利之耐 磨性之粉末可由以鉻作為主要之形成碳化物之金屬而獲 得’其限制條件為碳化物需足夠大。 【發明内容】 因此，本發明之一目的為提供一種用於製造具有高耐磨 性之粉末冶金產品的廉價鐵基粉末。 根據本發明’該目的以及由以下論述顯而易見之其他目 的係藉由退火預合金水霧化鐵基粉末來實現，該粉末包含 15至30重量％之（^、各自〇·5至5重量％之]^0、冒及v中之至 少一者及0.5至2重量％(較佳〇·7至2重量％且最佳1至2重量 %)之C ’其中鐵基粉末具有包含小於10重量％之Cr之基 吳’且其中鐵基粉末包含大石炭化鉻。 儘管發現15至30重量％範圍内之Cr含量產生足量之具有 合適類型、尺寸及硬度的碳化物，但發現丨8重量Q/。或丨8重 ϊ %以上之Cr含量進一步增強此效應且產生尤其高量之具 有合適類型、尺寸及硬度的碳化物。因此，在一些實施例 中’退火預合金水霧化鐵基粉末包含18至3〇重量％之Cr。 在一些實施例中，退火預合金水霧化鐵基粉末包含15至 30重量°/〇之Cr、0.5至5重量％之Mo及1至2重量％之C。 125100.doc 200829704 根據本發明，實現上述目的之此新賴粉末可藉由-種製 造鐵基粉末之方法而獲得，該方法包含使包括15至30重量 %^Cr、〇.5至5重量％之_、WAV中之至少_者及至2 重量％、較佳0.7至2重量％且最佳&重量％之〇之鐵基熔 融物經受水霧化以獲得鐵基粉末顆粒，及以足以在該等顆 粒内獲得大碳化物之溫度及㈣段使料粉末顆粒退火。 在較佳實施例中，已發現900至1 lOOt範圍内之溫度及 1 5至7 2小時範圍内之退火時間係足以在該等顆粒内獲得所 需碳化物。 在一些實施例中，鐵基熔融物包含18至3〇重量％之Cr。 在一些實施例乍，鐵基熔融物包含15至3 0重量％之cr、 〇·5至5重量。/。之Mo及1至2重量％之C。 【實施方式】 本發明之預合金粉末含有15至30重量％、較佳18至25重 里％之鉻，各自0.5至5重量％之铜、鶴及飢中之至少一 者；及0.5至2重量。/〇、較佳0.7至2重量％且最佳1至2重量％ 之石反，其餘為鐵、可選之其他合金元素及不可避免之雜 質。 預合金粉末可視情況包括其他合金元素，諸如至多3重 量％之鎢、至多3重量％之釩及至多2重量％之矽。亦可視 情況包括其他合金元素或添加物。在一實施例中，預合金 粉末包括至多2重量％之矽。 特定言之，應注意本發明之粉末中無需極為昂貴之碳化 物形成金屬鈮及鈦。 125100.doc 200829704 預合金粉末較佳具有40至100 μιη範圍内、較佳約80 μιη 之平均粒徑。 在較佳實施例中，預合金粉末由20至25重量％之Cr、1 至2重量❶/◦之Mo、1至2重量％之冒、0·5至1.5重量％之V、 0-2至1重量％之以、1至2重量％之c及餘量之Fe組成，或由 20至25重量％之Cr、2至4重量％之Mo、1至2重量％之C及 餘量之F e組成。 在其他較佳實施例中，預合金粉末由19至23重量❶/〇之 Cr、1至2重量％之Mo、1.5至3.5重量％之W、0.5至1.5重量 %之V、0.2至1重量％iSi、1至2重量％之(：及餘量之Fe組 成’或由20至25重量％之〇、2至4重量％之Mo、1至2重量 %之C及餘量之F e組成。 本發明粉末之碳化物較佳具有8至45 μιη範圍内、更佳8 至30 μπι範圍内之平均尺寸，且較佳佔總粉末之2〇至4〇體 積％。 由於碳化物具有不規則形狀，因此”尺寸"意謂如以顯微 鏡所量測之最長延伸部分。 儘官其他類型之大碳化物係合適的，但在一些實施例 中’本發明粉末之大碳化物為％3(：6型（M=Cr、Fe、Μ〇、 w)，亦即除作為主要碳化物形成元素之Cr以外，亦可存在 Fe、Mo及W中之一或多者。大碳化物亦可少量地含有除上 文規疋之奴化物形成元素以外之元素。 為獲彳于大奴化物’較佳在真空下使預合金粉末經受長時 間退火。退火較佳在9〇〇至11〇〇。〇範圍内、最佳在約 125100.doc 200829704 1000°C下進行，在此溫度下預合金粉末之鉻與碳反應形成 碳化鉻。 Οϋ The manufacture of products having high abrasion resistance can be based on, for example, powders such as iron or iron-based powders, including carbon in the form of carbides. Carbides are generally extremely hard and have a high (four), which provides high wear resistance characteristics in many applications. Due to this wear resistance, carbides often meet the needs of components in steels that require high grindability, such as high speed steel (hss), such as steel for drill presses, lathes, valve seats and the like. Examples of conventional iron-based powders having high wear resistance are disclosed, for example, in U.S. Patent No. 6,679,932, for a powder mixture comprising a tool steel powder and finely dispersed carbides, and a US patent for a non-Clock steel powder. No. $856,625. W, V, Mo, Ti, and Nb are elements capable of strongly forming carbides, which makes these elements particularly attractive for the manufacture of wear resistant products. Cr is another element that forms carbides. However, most of these conventionally known carbide-forming metals are expensive and result in inconvenient, high-priced products. Accordingly, there is a need in the powder metallurgy industry for an iron-based powder or high speed steel that provides sufficient wear resistance to a pressed and sintered product such as a valve seat or the like at a lower cost. 125100.doc 200829704 It is a cheaper and more readily available carbide-forming metal compared to other such metals for high wear resistance of conventional powders and hard phases. Therefore, it is preferable to use chromium as the main The metal forming the carbide. In this way, the powder can be produced more cheaply and thus a compacted product can be produced. In general, carbides of high speed steel are generally quite small, but in accordance with the present invention, it has now unexpectedly been shown that powders having equally advantageous wear resistance for, for example, valve seat applications can be formed from chromium as the primary carbide. The metal is obtained 'with the proviso that the carbide needs to be large enough. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an inexpensive iron-based powder for use in the manufacture of a powder metallurgy product having high wear resistance. According to the invention, this object and other objects which are apparent from the following discussion are achieved by annealing a pre-alloyed water atomized iron-based powder comprising 15 to 30% by weight of each of 5 to 5% by weight. And at least one of v and v and 0.5 to 2% by weight (preferably 〇7 to 2% by weight and most preferably 1 to 2% by weight) of C' wherein the iron-based powder has less than 10% by weight The base of Cr is 'and the iron-based powder contains large carbonized chromium. Although it is found that the Cr content in the range of 15 to 30% by weight produces a sufficient amount of carbide of a suitable type, size and hardness, it is found that 8 weight Q/ Or a Cr content of more than 8% 进一步 further enhances this effect and produces a particularly high amount of carbide of suitable type, size and hardness. Thus, in some embodiments the 'annealed prealloyed water atomized iron-based powder comprises 18 to 3 wt% of Cr. In some embodiments, the annealed prealloyed water atomized iron-based powder comprises 15 to 30 wt%/〇 of Cr, 0.5 to 5 wt% of Mo, and 1 to 2 wt% of C. 125100.doc 200829704 According to the present invention, this is achieved The lye powder can be obtained by a method for producing an iron-based powder, which comprises including 15 to 30% by weight of Cr, 〇.5 to 5% by weight of _, at least _ of WAV, and to 2% by weight, Preferably, 0.7 to 2% by weight and optimal &% by weight of the iron-based melt is subjected to water atomization to obtain iron-based powder particles, and at a temperature sufficient to obtain large carbides in the particles and (four) The powder particles are annealed. In a preferred embodiment, it has been found that temperatures in the range of 900 to 1 lOOt and annealing times in the range of 15 to 72 hours are sufficient to obtain the desired carbides within the particles. In an example, the iron-based melt contains 18 to 3 wt% of Cr. In some embodiments, the iron-based melt contains 15 to 30 wt% of cr, 〇·5 to 5 wt% of Mo and 1 Up to 2% by weight of C. [Embodiment] The prealloyed powder of the present invention contains 15 to 30% by weight, preferably 18 to 25% by weight of chromium, and 0.5 to 5% by weight of each of copper, crane and hunger. And 0.5 to 2% by weight, preferably 0.7 to 2% by weight and most preferably 1 to 2% by weight of the stone, the balance being iron Optional other alloying elements and unavoidable impurities. The prealloyed powder may optionally include other alloying elements such as up to 3% by weight of tungsten, up to 3% by weight of vanadium and up to 2% by weight of bismuth. Other alloys may optionally be included Element or additive. In one embodiment, the prealloyed powder comprises up to 2% by weight of niobium. In particular, it should be noted that the powder of the present invention does not require extremely expensive carbides to form niobium and titanium. 125100.doc 200829704 Pre The alloy powder preferably has an average particle diameter in the range of 40 to 100 μm, preferably about 80 μm. In a preferred embodiment, the prealloyed powder consists of 20 to 25% by weight of Cr, 1 to 2 parts by weight of lanthanum/lanthan Mo, 1 to 2% by weight of escaping, 0.5 to 1.5% by weight of V, 0-2. To 1% by weight, 1 to 2% by weight of c and the balance of Fe composition, or from 20 to 25% by weight of Cr, 2 to 4% by weight of Mo, 1 to 2% by weight of C and the balance F e composition. In other preferred embodiments, the prealloyed powder is from 19 to 23 parts by weight of ruthenium/iridium, from 1 to 2% by weight of Mo, from 1.5 to 3.5% by weight of W, from 0.5 to 1.5% by weight of V, from 0.2 to 1 by weight. %iSi, 1 to 2% by weight of (and the balance of Fe composition' or from 20 to 25% by weight of bismuth, 2 to 4% by weight of Mo, 1 to 2% by weight of C and the balance of F e The carbide of the powder of the present invention preferably has an average size in the range of 8 to 45 μm, more preferably 8 to 30 μm, and preferably 2 to 4% by volume of the total powder. Shape, and thus "size" means the longest extension as measured by a microscope. It is desirable to use other types of large carbides, but in some embodiments 'the large carbide of the powder of the invention is %3 ( : Type 6 (M=Cr, Fe, Μ〇, w), that is, in addition to Cr which is a main carbide forming element, one or more of Fe, Mo and W may be present. Large carbides may also be small. The ground contains elements other than the sulphate forming elements of the above formula. In order to obtain the large slag, it is preferred to subject the prealloyed powder to a vacuum. Annealing time. Preferably, annealing, performed the best in the range of about 9〇〇 to 11〇〇.〇 at 125100.doc 200829704 1000 ° C, the chromium carbide is formed at a temperature of chromium prealloyed powder reacts with carbon. O
在退火期間，新穎碳化物形成並生長，且現有碳化物藉 由鉻與碳之間之反應而繼續生長。退火較佳持續15至72小 時、更佳持續48小時以上，以便獲得所需尺寸之碳化物。 退火持續時間愈長，則碳化物晶粒生長愈大。然而，若退 火持續报長時間，則其消耗大量能量且可能成為生產流程 瓶頭因此，雖然約20至3 0 μηι之平均碳化物晶粒尺寸可 為农仏的但當平均碳化物晶粒尺寸為約1 0 μιη時，視優 先級而定，就經濟學觀點而言更便利的為較早地終止退 火0 使用自退火溫度極緩慢冷卻，較佳為12小時Μ工、 冷卻：使得碳化物可進一步生長，因為較大量之碳化物: 車低m度下係熱力學穩定的。緩慢冷卻亦將確保基質變成 鐵磁體itb對於粉末之可壓縮性而言係重要的。 示：化物之生長以外，使粉末退火亦具有其他優點。 在U火功間，基質晶粒亦生長且由於水霧化所獲得之粉 末顆粒的固有麻士〜 〜力侍以鬆弛。該等因素使得粉末硬度更低 且更易於壓實，合，丨^ , 、 ^ 例如向粉末提供更高之可壓縮性。 在退火期間可含周 κ ^ P私末之奴及氧含量。通常需要保持低 氧含篁。在退火Λ ^間’碳與氧反應形成氣態碳氧化物，此 降低粉末之氧含息 里。若預合金粉末本身無足夠之碳用以形 = 降低氧含量，則可為退火提供石墨粉末形式之 額外碳。 尽乂骂之 125100.doc 200829704 由於在退火期間，預合金粉末之大部分鉻自基質轉移至 碳化物，因此所得退火粉末之基質具有小於該基質丨〇重量 %、較佳小於9重量％且最佳小於8重量％之溶解鉻含量， 故粉末並非不鏽的。 粉末之基質組合物係經設計以使得肥粒鐵在燒結期間轉 化為沃斯田鐵（austenite)。因此，燒結後一旦冷卻，沃斯 田鐵即可轉化為麻田散鐵（martensite)。麻田散鐵基質中之 〇 大碳化物將向壓製及燒結組件提供良好耐磨性。 雖然本發明粉末之碳化物之主體為碳化鉻，但一些碳化 物亦可由預合金粉末中之其他碳化物形成化合物（諸如上 文提及之鉬、鎢及釩）來形成。 在壓實及燒結之前，可將本發明之退火粉末與其他粉末 ' 組份（諸如其他鐵基粉末、石墨、蒸發潤滑劑、固體潤滑 剤、可加工性增強劑等）混合，以製造具有高耐磨性之產 品。例如，可將本發明粉末與純鐵粉末及石墨粉末混合， Q 或與不鏽鋼粉末混合。可添加有助於壓實且隨後在燒結期 間瘵發之潤滑劑（諸如蠟、硬脂酸鹽、金屬皂或其類似物） 以及固體潤滑劑（諸如MnS、CaF2、M。^，潤滑劑減少在 使用燒結產品期間之摩擦且亦可增強其可加工性。亦可添 加其他可加工性增強劑以及粉末冶金領域之其他習知添加 物0 實例1 將21.5重里％之Cr、j 5重量重量％之界、工 重量％之¥、0.5重量％之以、15重量％之。及餘量之卜的熔 125100.doc 200829704 融物水霧化以形成預合金粉末。隨後將所獲得之粉末在 1000°C下真空退火約48小時，總退火時間為約60小時，此 後粉末顆粒在鐵磁體基質中含有約3 〇體積％之平均晶粒尺 寸為約10 μιη之碳化鉻。 實例2During annealing, novel carbides form and grow, and existing carbides continue to grow by the reaction between chromium and carbon. Annealing preferably lasts from 15 to 72 hours, more preferably for more than 48 hours, to obtain carbides of the desired size. The longer the annealing duration, the larger the carbide grain growth. However, if the annealing continues for a long time, it consumes a lot of energy and may become the bottle of the production process. Therefore, although the average carbide grain size of about 20 to 30 μηι can be agricultural, but the average carbide grain size When it is about 10 μιη, depending on the priority, it is more convenient from an economic point of view to terminate the annealing earlier. Using self-annealing temperature, very slow cooling, preferably 12 hours of completion, cooling: making carbide It can be further grown because of the larger amount of carbide: the car is thermodynamically stable at low m degrees. Slow cooling will also ensure that the matrix becomes ferromagnetic itb is important for the compressibility of the powder. In addition to the growth of the compound, annealing the powder also has other advantages. During the U-fire work, the matrix grains also grow and the inherent mass of the powder particles obtained by water atomization is relaxed. These factors make the powder less rigid and easier to compact, such as 丨^, , ^, for example, to provide a higher compressibility to the powder. During the annealing period, it may contain weekly κ ^ P private slaves and oxygen content. It is often necessary to maintain a low oxygen content. During annealing, the carbon reacts with oxygen to form gaseous carbon oxides, which reduces the oxygen content of the powder. If the prealloyed powder itself does not have enough carbon to form = reduce the oxygen content, it can provide additional carbon in the form of graphite powder for annealing. 125100.doc 200829704 Since most of the chromium of the prealloyed powder is transferred from the substrate to the carbide during annealing, the matrix of the resulting annealed powder has less than the weight of the substrate, preferably less than 9% by weight and most Preferably, the dissolved chromium content is less than 8% by weight, so the powder is not stainless. The matrix composition of the powder is designed such that the ferrite iron is converted to austenite during sintering. Therefore, once cooled, the Worth Iron can be converted into a martensite. The large carbides in the Ma Tian loose iron matrix will provide good wear resistance to the pressed and sintered components. Although the bulk of the carbide of the powder of the present invention is chromium carbide, some of the carbide may be formed from other carbide forming compounds in the prealloyed powder such as molybdenum, tungsten and vanadium as mentioned above. The annealed powder of the present invention may be mixed with other powder components (such as other iron-based powders, graphite, evaporative lubricants, solid lubricants, workability enhancers, etc.) prior to compaction and sintering to produce high Abrasion resistant products. For example, the powder of the present invention may be mixed with pure iron powder and graphite powder, Q or mixed with stainless steel powder. Lubricants (such as waxes, stearates, metal soaps or the like) which aid in compaction and subsequent bursting during sintering, as well as solid lubricants (such as MnS, CaF2, M. Friction during the use of the sintered product can also enhance its processability. Other processability enhancers and other conventional additives in the field of powder metallurgy can also be added. 0 Example 1 21.5 wt% of Cr, j 5 wt% The boundary, the weight of the work%, the 0.5% by weight, the 15% by weight, and the balance of the melt 125100.doc 200829704 The melt water is atomized to form a prealloyed powder. The obtained powder is then 1000. Vacuum annealing at ° C for about 48 hours, the total annealing time is about 60 hours, after which the powder particles contain about 3% by volume of chromium carbide having an average grain size of about 10 μm in the ferromagnetic matrix.
將21.5重量％之〇、3重量％之撾〇、15重量％之〇及餘量 之Fe的熔融物水霧化以形成預合金粉末。隨後將所獲得之 粉末在100(TC下真空退火約48小時，總退火時間為約6〇小 時，此後粉末顆粒在鐵磁體基質中含有約3 〇體積％之平均 晶粒尺寸為約1 〇 pm之碳化鉻。 實例3 將21·0重量％之〇、h5重量％iM〇、2·5重量。之w、ι 重量％之乂、〇·5重量％之8卜重量0/<c及餘量之卜的熔 融物水霧化以形成預合金粉末。隨後將所獲得之粉末在 1000 C下真空退火約48小時，總退火時間為約6〇小時，此 後粉末顆粒在鐵磁體基質中含有約3〇體積％之平均晶粒尺 寸為約10 μιη之碳化鉻。 量％之石墨及0,75 將所獲得之粉末（下文稱為Α3)與〇·5重 重量％之蒸發賴劑混合。在胳之遷力下將混合物 壓實成測試棒。在90^/10¾之氣氛下於U2〇t：之溫度下 燒結所獲得之樣品。燒結後，佶揭口 〜、、口佼便樣口口在液氮中經受低溫冷 卻，接著在550°C下回火。 製備基於已知HSS粉末M3/2之類似混合物，且使用與 文所述方法相同之方法製造測試棒。 125100.doc -12- 200829704 使’則"式棒經受根據維氏方法（Vickers method)之硬度測 減。在二個不同溫度（300/400/500。〇下測試熱硬度。結果 概括於下表中。A melt of 21.5 wt% of bismuth, 3% by weight of lanthanum, 15% by weight of lanthanum and the balance of Fe was atomized to form a prealloyed powder. The obtained powder was then vacuum annealed at 100 (TC for about 48 hours, and the total annealing time was about 6 hrs, after which the powder particles contained about 3% by volume in the ferromagnetic matrix and the average grain size was about 1 〇 pm. Chromium carbide. Example 3 21.0% by weight, h5 wt% iM〇, 2.5 weight, w, ι% by weight, 〇·5 wt%, 8 b weight 0/<c and The remainder of the melt is atomized by water to form a prealloyed powder. The obtained powder is then vacuum annealed at 1000 C for about 48 hours, and the total annealing time is about 6 hours, after which the powder particles are contained in the ferromagnetic matrix. About 3% by volume of chromium carbide having an average grain size of about 10 μm. Amount of graphite and 0,75 The obtained powder (hereinafter referred to as Α3) was mixed with 5% by weight of an evaporation agent. The mixture was compacted into a test rod under the influence of the force of the force. The obtained sample was sintered at a temperature of 90 ° / 103⁄4 at a temperature of U 2 〇 t: After sintering, the 佶 口 mouth, mouth 佼 mouth sample The mouth was subjected to cryogenic cooling in liquid nitrogen followed by tempering at 550 ° C. Preparation based on known HSS powder M3/ A similar mixture of 2, and the test rod was fabricated using the same method as described herein. 125100.doc -12- 200829704 The 'then" bar was subjected to hardness reduction according to the Vickers method. The heat hardness was tested at different temperatures (300/400/500. The results are summarized in the table below.
A3測試材料之顯微結構（參見圖1)由麻田散鐵基質中之 許多大碳化物組成，而參考材料具有在麻田散鐵基質中具 有顯著較小碳化物之顯微結構（參見圖2)。 A3材料具有稍微高於M3/2材料之孔隙率，此解釋了雖 然兩種材料之顯微硬度值（HV0.025)幾乎相同，但A3硬度 值（HV5)低於M3/2硬度值之原因。在pm VSI組件之製造 Ο 中’通#在燒結期間藉由銅滲入來消除孔隙率且因此可忽 略該等效應。鑒於此，A3材料之硬度值可與參考M3/2材 料之硬度值相當，此良好地指示該等材料應具有相當之耐 磨性。特定言之，在高溫下維持硬度對於VSI應用中之耐 磨性而言係重要的。熱硬度測試結果展示八3材料滿足該等 要求。 實例4 將21·5重篁％之〇、3重量％之撾〇、1.5重量％之c及餘量 之Fe的嫁融物水霧化以形成預合金粉末。隨後將所獲得之 粉末在100(TC下真空退火約48小時，總退火時間為約6〇小 時’此後粉末顆粒在鐵磁體基質中含有約3〇體積％之平均 125100.doc -13- 200829704 晶粒尺寸為約10 μηι之碳化鉻。 处/、〇·5重里/〇之石墨及〇·75重量0/◦之蒸發潤滑劑混合 之該粉末以便以與實例3中相同之方式製造測試棒，導致 與圖1中之顯微結構極為類似之顯微紐 【圖式簡單說明】 、、、。構。 圖1展不A3基測試材料之顯微結構。 圖2展示Μ3/2基測試材料0 〇The microstructure of the A3 test material (see Figure 1) consists of many large carbides in the granulated iron matrix, while the reference material has a microstructure with significantly smaller carbides in the granulated iron matrix (see Figure 2). . The A3 material has a slightly higher porosity than the M3/2 material, which explains why the A3 hardness value (HV5) is lower than the M3/2 hardness value although the microhardness values (HV0.025) of the two materials are almost the same. . In the manufacture of the pm VSI component, the 'passage' is eliminated by copper infiltration during sintering and thus the effects can be neglected. In view of this, the hardness value of the A3 material can be comparable to the hardness value of the reference M3/2 material, which is a good indication that the materials should have comparable wear resistance. In particular, maintaining hardness at elevated temperatures is important for wear resistance in VSI applications. The hot hardness test results show that the eight 3 materials meet these requirements. Example 4 A jelly of 21.5 % by weight of hydrazine, 3% by weight of lanthanum, 1.5% by weight of c and the balance of Fe was atomized to form a prealloyed powder. The obtained powder was then vacuum annealed at 100 (TC for about 48 hours, and the total annealing time was about 6 hrs). Thereafter, the powder particles contained about 3% by volume of the average of 125100.doc -13-200829704 crystal in the ferromagnetic matrix. The powder having a particle size of about 10 μηι is mixed with the graphite of /·············································· The microscopic structure which is very similar to the microstructure in Fig. 1 [simple description of the drawing], , and structure. Figure 1 shows the microstructure of the A3-based test material. Figure 2 shows the Μ3/2-based test material. 〇
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